workflow: Split workflow module in API and service module

51 files changed, 431 insertions, 299 deletions

diff --git a/simulator/README.md b/simulator/README.md
index 61ef1d43..d02925d6 100644
--- a/simulator/README.md
+++ b/simulator/README.md
@@ -23,7 +23,7 @@ This component is responsible for modelling and simulation of datacenters and th
 - **[opendc-compute](opendc-compute)**  
   The [Infrastructure as a Service](https://en.wikipedia.org/wiki/Infrastructure_as_a_Service) (IaaS) component of OpenDC for computing infrastructure (similar to 
   [Amazon EC2](https://aws.amazon.com/ec2/) and [Google Compute Engine](https://cloud.google.com/compute)).
-- **[opendc-workflows](opendc-workflows)**  
+- **[opendc-workflow](opendc-workflow)**  
   Workflow orchestration service built on top of OpenDC. 
 - **[opendc-format](opendc-format)**  
   Collection of libraries for processing data formats related to (simulation of) cloud computing and datacenters. 
diff --git a/simulator/opendc-experiments/opendc-experiments-sc18/build.gradle.kts b/simulator/opendc-experiments/opendc-experiments-sc18/build.gradle.kts
index f85d9b19..02e77c7c 100644
--- a/simulator/opendc-experiments/opendc-experiments-sc18/build.gradle.kts
+++ b/simulator/opendc-experiments/opendc-experiments-sc18/build.gradle.kts
@@ -32,7 +32,7 @@ dependencies {
     api(platform(project(":opendc-platform")))
     api(project(":opendc-harness"))
     implementation(project(":opendc-format"))
-    implementation(project(":opendc-workflows"))
+    implementation(project(":opendc-workflow:opendc-workflow-service"))
     implementation(project(":opendc-simulator:opendc-simulator-core"))
     implementation(project(":opendc-compute:opendc-compute-simulator"))
 }
diff --git a/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/UnderspecificationExperiment.kt b/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/UnderspecificationExperiment.kt
index 2be05119..9e305b3d 100644
--- a/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/UnderspecificationExperiment.kt
+++ b/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/UnderspecificationExperiment.kt
@@ -35,13 +35,13 @@ import org.opendc.simulator.compute.SimSpaceSharedHypervisorProvider
 import org.opendc.simulator.utils.DelayControllerClockAdapter
 import org.opendc.trace.core.EventTracer
 import org.opendc.trace.core.enable
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.WorkflowEvent
-import org.opendc.workflows.service.WorkflowSchedulerMode
-import org.opendc.workflows.service.stage.job.NullJobAdmissionPolicy
-import org.opendc.workflows.service.stage.job.SubmissionTimeJobOrderPolicy
-import org.opendc.workflows.service.stage.task.NullTaskEligibilityPolicy
-import org.opendc.workflows.service.stage.task.SubmissionTimeTaskOrderPolicy
+import org.opendc.workflow.service.WorkflowEvent
+import org.opendc.workflow.service.WorkflowService
+import org.opendc.workflow.service.scheduler.WorkflowSchedulerMode
+import org.opendc.workflow.service.scheduler.job.NullJobAdmissionPolicy
+import org.opendc.workflow.service.scheduler.job.SubmissionTimeJobOrderPolicy
+import org.opendc.workflow.service.scheduler.task.NullTaskEligibilityPolicy
+import org.opendc.workflow.service.scheduler.task.SubmissionTimeTaskOrderPolicy
 import java.io.File
 import java.io.FileInputStream
 import kotlin.math.max
@@ -106,8 +106,8 @@ public class UnderspecificationExperiment : Experiment("underspecification") {
 
             hosts.forEach { compute.addHost(it) }
 
-            val scheduler = StageWorkflowService(
-                testScope,
+            val scheduler = WorkflowService(
+                testScope.coroutineContext,
                 clock,
                 tracer,
                 compute.newClient(),
diff --git a/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/WorkflowMetrics.kt b/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/WorkflowMetrics.kt
index dbd04b87..a8356888 100644
--- a/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/WorkflowMetrics.kt
+++ b/simulator/opendc-experiments/opendc-experiments-sc18/src/main/kotlin/org/opendc/experiments/sc18/WorkflowMetrics.kt
@@ -24,7 +24,7 @@ package org.opendc.experiments.sc18
 
 import org.opendc.trace.core.EventStream
 import org.opendc.trace.core.onEvent
-import org.opendc.workflows.service.WorkflowEvent
+import org.opendc.workflow.service.WorkflowEvent
 import java.util.*
 import kotlin.coroutines.resume
 import kotlin.coroutines.suspendCoroutine
diff --git a/simulator/opendc-format/build.gradle.kts b/simulator/opendc-format/build.gradle.kts
index 4c0f6dcd..385e556d 100644
--- a/simulator/opendc-format/build.gradle.kts
+++ b/simulator/opendc-format/build.gradle.kts
@@ -31,7 +31,7 @@ plugins {
 dependencies {
     api(platform(project(":opendc-platform")))
     api(project(":opendc-compute:opendc-compute-api"))
-    api(project(":opendc-workflows"))
+    api(project(":opendc-workflow:opendc-workflow-api"))
     implementation(project(":opendc-simulator:opendc-simulator-compute"))
     implementation(project(":opendc-compute:opendc-compute-simulator"))
     api("com.fasterxml.jackson.module:jackson-module-kotlin:${versions["jackson-module-kotlin"]}")
diff --git a/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/gwf/GwfTraceReader.kt b/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/gwf/GwfTraceReader.kt
index f510271b..e68afeb7 100644
--- a/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/gwf/GwfTraceReader.kt
+++ b/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/gwf/GwfTraceReader.kt
@@ -25,10 +25,10 @@ package org.opendc.format.trace.gwf
 import org.opendc.format.trace.TraceEntry
 import org.opendc.format.trace.TraceReader
 import org.opendc.simulator.compute.workload.SimFlopsWorkload
-import org.opendc.workflows.workload.Job
-import org.opendc.workflows.workload.Task
-import org.opendc.workflows.workload.WORKFLOW_TASK_CORES
-import org.opendc.workflows.workload.WORKFLOW_TASK_DEADLINE
+import org.opendc.workflow.api.Job
+import org.opendc.workflow.api.Task
+import org.opendc.workflow.api.WORKFLOW_TASK_CORES
+import org.opendc.workflow.api.WORKFLOW_TASK_DEADLINE
 import java.io.BufferedReader
 import java.io.File
 import java.io.InputStream
diff --git a/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/wtf/WtfTraceReader.kt b/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/wtf/WtfTraceReader.kt
index 3d969eb7..feadf61f 100644
--- a/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/wtf/WtfTraceReader.kt
+++ b/simulator/opendc-format/src/main/kotlin/org/opendc/format/trace/wtf/WtfTraceReader.kt
@@ -28,10 +28,10 @@ import org.apache.parquet.avro.AvroParquetReader
 import org.opendc.format.trace.TraceEntry
 import org.opendc.format.trace.TraceReader
 import org.opendc.simulator.compute.workload.SimFlopsWorkload
-import org.opendc.workflows.workload.Job
-import org.opendc.workflows.workload.Task
-import org.opendc.workflows.workload.WORKFLOW_TASK_CORES
-import org.opendc.workflows.workload.WORKFLOW_TASK_DEADLINE
+import org.opendc.workflow.api.Job
+import org.opendc.workflow.api.Task
+import org.opendc.workflow.api.WORKFLOW_TASK_CORES
+import org.opendc.workflow.api.WORKFLOW_TASK_DEADLINE
 import java.util.UUID
 import kotlin.math.min
 
diff --git a/simulator/opendc-workflow/build.gradle.kts b/simulator/opendc-workflow/build.gradle.kts
new file mode 100644
index 00000000..3cefa409
--- /dev/null
+++ b/simulator/opendc-workflow/build.gradle.kts
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+description = "Workflow orchestration for OpenDC"
diff --git a/simulator/opendc-workflow/opendc-workflow-api/build.gradle.kts b/simulator/opendc-workflow/opendc-workflow-api/build.gradle.kts
new file mode 100644
index 00000000..d3e67bee
--- /dev/null
+++ b/simulator/opendc-workflow/opendc-workflow-api/build.gradle.kts
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+description = "Workflow orchestration service API for OpenDC"
+
+/* Build configuration */
+plugins {
+    `kotlin-library-conventions`
+}
+
+dependencies {
+    api(platform(project(":opendc-platform")))
+    api(project(":opendc-compute:opendc-compute-api"))
+    implementation(project(":opendc-utils"))
+    implementation("io.github.microutils:kotlin-logging")
+}
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/workload/Job.kt b/simulator/opendc-workflow/opendc-workflow-api/src/main/kotlin/org/opendc/workflow/api/Job.kt
index 53116cb6..5e8b0b9e 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/workload/Job.kt
+++ b/simulator/opendc-workflow/opendc-workflow-api/src/main/kotlin/org/opendc/workflow/api/Job.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +20,7 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.workload
+package org.opendc.workflow.api
 
 import java.util.*
 
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/workload/Metadata.kt b/simulator/opendc-workflow/opendc-workflow-api/src/main/kotlin/org/opendc/workflow/api/Metadata.kt
index 4305aa57..db208998 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/workload/Metadata.kt
+++ b/simulator/opendc-workflow/opendc-workflow-api/src/main/kotlin/org/opendc/workflow/api/Metadata.kt
@@ -22,7 +22,7 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.workload
+package org.opendc.workflow.api
 
 /**
  * Meta-data key for the deadline of a task.
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/workload/Task.kt b/simulator/opendc-workflow/opendc-workflow-api/src/main/kotlin/org/opendc/workflow/api/Task.kt
index 4ccefef9..d91f9879 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/workload/Task.kt
+++ b/simulator/opendc-workflow/opendc-workflow-api/src/main/kotlin/org/opendc/workflow/api/Task.kt
@@ -1,7 +1,5 @@
 /*
- * MIT License
- *
- * Copyright (c) 2019 atlarge-research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,7 +20,7 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.workload
+package org.opendc.workflow.api
 
 import java.util.*
 
diff --git a/simulator/opendc-workflows/build.gradle.kts b/simulator/opendc-workflow/opendc-workflow-service/build.gradle.kts
index 541d379e..12a54235 100644
--- a/simulator/opendc-workflows/build.gradle.kts
+++ b/simulator/opendc-workflow/opendc-workflow-service/build.gradle.kts
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,7 +20,7 @@
  * SOFTWARE.
  */
 
-description = "Workflow service for OpenDC"
+description = "Workflow orchestration service for OpenDC"
 
 /* Build configuration */
 plugins {
@@ -30,6 +30,7 @@ plugins {
 
 dependencies {
     api(platform(project(":opendc-platform")))
+    api(project(":opendc-workflow:opendc-workflow-api"))
     api(project(":opendc-compute:opendc-compute-api"))
     api(project(":opendc-trace:opendc-trace-core"))
     implementation(project(":opendc-utils"))
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/WorkflowEvent.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowEvent.kt
index bcf93562..bb2ad6c6 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/WorkflowEvent.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowEvent.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,11 +20,11 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service
 
 import org.opendc.trace.core.Event
-import org.opendc.workflows.workload.Job
-import org.opendc.workflows.workload.Task
+import org.opendc.workflow.api.Job
+import org.opendc.workflow.api.Task
 
 /**
  * An event emitted by the [WorkflowService].
diff --git a/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowService.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowService.kt
new file mode 100644
index 00000000..2f83e376
--- /dev/null
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/WorkflowService.kt
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.workflow.service
+
+import kotlinx.coroutines.flow.Flow
+import org.opendc.compute.api.ComputeClient
+import org.opendc.trace.core.EventTracer
+import org.opendc.workflow.api.Job
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
+import org.opendc.workflow.service.scheduler.WorkflowSchedulerMode
+import org.opendc.workflow.service.scheduler.job.JobAdmissionPolicy
+import org.opendc.workflow.service.scheduler.job.JobOrderPolicy
+import org.opendc.workflow.service.scheduler.task.TaskEligibilityPolicy
+import org.opendc.workflow.service.scheduler.task.TaskOrderPolicy
+import java.time.Clock
+import kotlin.coroutines.CoroutineContext
+
+/**
+ * A service for cloud workflow management.
+ *
+ * The workflow scheduler is modelled after the Reference Architecture for Topology Scheduling by Andreadis et al.
+ */
+public interface WorkflowService : AutoCloseable {
+    /**
+     * The events emitted by the workflow scheduler.
+     */
+    public val events: Flow<WorkflowEvent>
+
+    /**
+     * Submit the specified [Job] to the workflow service for scheduling.
+     */
+    public suspend fun submit(job: Job)
+
+    /**
+     * Terminate the lifecycle of the workflow service, stopping all running workflows.
+     */
+    public override fun close()
+
+    public companion object {
+        /**
+         * Construct a new [WorkflowService] implementation.
+         *
+         * @param context The [CoroutineContext] to use in the service.
+         * @param clock The clock instance to use.
+         * @param tracer The event tracer to use.
+         * @param compute The compute client to use.
+         * @param mode The scheduling mode to use.
+         * @param jobAdmissionPolicy The job admission policy to use.
+         * @param jobOrderPolicy The job order policy to use.
+         * @param taskEligibilityPolicy The task eligibility policy to use.
+         * @param taskOrderPolicy The task order policy to use.
+         */
+        public operator fun invoke(
+            context: CoroutineContext,
+            clock: Clock,
+            tracer: EventTracer,
+            compute: ComputeClient,
+            mode: WorkflowSchedulerMode,
+            jobAdmissionPolicy: JobAdmissionPolicy,
+            jobOrderPolicy: JobOrderPolicy,
+            taskEligibilityPolicy: TaskEligibilityPolicy,
+            taskOrderPolicy: TaskOrderPolicy
+        ): WorkflowService {
+            return WorkflowServiceImpl(
+                context,
+                clock,
+                tracer,
+                compute,
+                mode,
+                jobAdmissionPolicy,
+                jobOrderPolicy,
+                taskEligibilityPolicy,
+                taskOrderPolicy
+            )
+        }
+    }
+}
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/JobState.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/JobState.kt
index 89849f6a..1bb67169 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/JobState.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/JobState.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,9 +20,9 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service.internal
 
-import org.opendc.workflows.workload.Job
+import org.opendc.workflow.api.Job
 
 public class JobState(public val job: Job, public val submittedAt: Long) {
     /**
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/TaskState.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/TaskState.kt
index ef9714c2..c3ce1492 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/TaskState.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/TaskState.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,10 +20,10 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service.internal
 
 import org.opendc.compute.api.Server
-import org.opendc.workflows.workload.Task
+import org.opendc.workflow.api.Task
 
 public class TaskState(public val job: JobState, public val task: Task) {
     /**
@@ -39,12 +39,12 @@ public class TaskState(public val job: JobState, public val task: Task) {
     /**
      * The dependencies of this task.
      */
-    public val dependencies: HashSet<TaskState> = HashSet<TaskState>()
+    public val dependencies: HashSet<TaskState> = HashSet()
 
     /**
      * The dependents of this task.
      */
-    public val dependents: HashSet<TaskState> = HashSet<TaskState>()
+    public val dependents: HashSet<TaskState> = HashSet()
 
     /**
      * A flag to indicate whether this workflow task instance is a workflow root.
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/TaskStatus.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/TaskStatus.kt
index 99f5bb87..fe941d09 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/TaskStatus.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/TaskStatus.kt
@@ -1,7 +1,5 @@
 /*
- * MIT License
- *
- * Copyright (c) 2020 atlarge-research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,7 +20,7 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service.internal
 
 /**
  * The state of a workflow task.
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/StageWorkflowSchedulerListener.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowSchedulerListener.kt
index 18721889..29c6aeea 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/StageWorkflowSchedulerListener.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowSchedulerListener.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,11 +20,11 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service.internal
 
-public interface StageWorkflowSchedulerListener {
-    public fun cycleStarted(scheduler: StageWorkflowService) {}
-    public fun cycleFinished(scheduler: StageWorkflowService) {}
+public interface WorkflowSchedulerListener {
+    public fun cycleStarted(scheduler: WorkflowServiceImpl) {}
+    public fun cycleFinished(scheduler: WorkflowServiceImpl) {}
 
     public fun jobSubmitted(job: JobState) {}
     public fun jobStarted(job: JobState) {}
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/StageWorkflowService.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowServiceImpl.kt
index c5c4bf97..85a88acd 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/StageWorkflowService.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/internal/WorkflowServiceImpl.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,10 +20,11 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service.internal
 
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.cancel
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.launch
@@ -32,21 +33,24 @@ import org.opendc.compute.api.*
 import org.opendc.trace.core.EventTracer
 import org.opendc.trace.core.consumeAsFlow
 import org.opendc.trace.core.enable
-import org.opendc.workflows.service.stage.job.JobAdmissionPolicy
-import org.opendc.workflows.service.stage.job.JobOrderPolicy
-import org.opendc.workflows.service.stage.task.TaskEligibilityPolicy
-import org.opendc.workflows.service.stage.task.TaskOrderPolicy
-import org.opendc.workflows.workload.Job
-import org.opendc.workflows.workload.WORKFLOW_TASK_CORES
+import org.opendc.workflow.api.Job
+import org.opendc.workflow.api.WORKFLOW_TASK_CORES
+import org.opendc.workflow.service.*
+import org.opendc.workflow.service.scheduler.WorkflowSchedulerMode
+import org.opendc.workflow.service.scheduler.job.JobAdmissionPolicy
+import org.opendc.workflow.service.scheduler.job.JobOrderPolicy
+import org.opendc.workflow.service.scheduler.task.TaskEligibilityPolicy
+import org.opendc.workflow.service.scheduler.task.TaskOrderPolicy
 import java.time.Clock
 import java.util.*
+import kotlin.coroutines.CoroutineContext
 
 /**
  * A [WorkflowService] that distributes work through a multi-stage process based on the Reference Architecture for
  * Datacenter Scheduling.
  */
-public class StageWorkflowService(
-    internal val coroutineScope: CoroutineScope,
+public class WorkflowServiceImpl(
+    context: CoroutineContext,
     internal val clock: Clock,
     internal val tracer: EventTracer,
     private val computeClient: ComputeClient,
@@ -57,6 +61,11 @@ public class StageWorkflowService(
     taskOrderPolicy: TaskOrderPolicy
 ) : WorkflowService, ServerWatcher {
     /**
+     * The [CoroutineScope] of the service bounded by the lifecycle of the service.
+     */
+    internal val scope = CoroutineScope(context)
+
+    /**
      * The logger instance to use.
      */
     private val logger = KotlinLogging.logger {}
@@ -99,17 +108,17 @@ public class StageWorkflowService(
     /**
      * The root listener of this scheduler.
      */
-    private val rootListener = object : StageWorkflowSchedulerListener {
+    private val rootListener = object : WorkflowSchedulerListener {
         /**
          * The listeners to delegate to.
          */
-        val listeners = mutableSetOf<StageWorkflowSchedulerListener>()
+        val listeners = mutableSetOf<WorkflowSchedulerListener>()
 
-        override fun cycleStarted(scheduler: StageWorkflowService) {
+        override fun cycleStarted(scheduler: WorkflowServiceImpl) {
             listeners.forEach { it.cycleStarted(scheduler) }
         }
 
-        override fun cycleFinished(scheduler: StageWorkflowService) {
+        override fun cycleFinished(scheduler: WorkflowServiceImpl) {
             listeners.forEach { it.cycleFinished(scheduler) }
         }
 
@@ -153,7 +162,7 @@ public class StageWorkflowService(
         this.jobQueue = PriorityQueue(100, jobOrderPolicy(this).thenBy { it.job.uid })
         this.taskEligibilityPolicy = taskEligibilityPolicy(this)
         this.taskQueue = PriorityQueue(1000, taskOrderPolicy(this).thenBy { it.task.uid })
-        coroutineScope.launch {
+        scope.launch {
             image = computeClient.newImage("workflow-runner")
         }
     }
@@ -194,6 +203,10 @@ public class StageWorkflowService(
         requestCycle()
     }
 
+    override fun close() {
+        scope.cancel()
+    }
+
     /**
      * Indicate to the scheduler that a scheduling cycle is needed.
      */
@@ -218,7 +231,12 @@ public class StageWorkflowService(
             iterator.remove()
             jobQueue.add(jobInstance)
             activeJobs += jobInstance
-            tracer.commit(WorkflowEvent.JobStarted(this, jobInstance.job))
+            tracer.commit(
+                WorkflowEvent.JobStarted(
+                    this,
+                    jobInstance.job
+                )
+            )
             rootListener.jobStarted(jobInstance)
         }
 
@@ -263,15 +281,25 @@ public class StageWorkflowService(
 
             val cores = instance.task.metadata[WORKFLOW_TASK_CORES] as? Int ?: 1
             val image = image
-            coroutineScope.launch {
-                val flavor = computeClient.newFlavor(instance.task.name, cores, 1000) // TODO How to determine memory usage for workflow task
-                val server = computeClient.newServer(instance.task.name, image, flavor, start = false, meta = instance.task.metadata)
+            scope.launch {
+                val flavor = computeClient.newFlavor(
+                    instance.task.name,
+                    cores,
+                    1000
+                ) // TODO How to determine memory usage for workflow task
+                val server = computeClient.newServer(
+                    instance.task.name,
+                    image,
+                    flavor,
+                    start = false,
+                    meta = instance.task.metadata
+                )
 
                 instance.state = TaskStatus.ACTIVE
                 instance.server = server
                 taskByServer[server] = instance
 
-                server.watch(this@StageWorkflowService)
+                server.watch(this@WorkflowServiceImpl)
                 server.start()
             }
 
@@ -283,13 +311,14 @@ public class StageWorkflowService(
 
     public override fun onStateChanged(server: Server, newState: ServerState) {
         when (newState) {
-            ServerState.PROVISIONING -> {}
+            ServerState.PROVISIONING -> {
+            }
             ServerState.RUNNING -> {
                 val task = taskByServer.getValue(server)
                 task.startedAt = clock.millis()
                 tracer.commit(
                     WorkflowEvent.TaskStarted(
-                        this@StageWorkflowService,
+                        this@WorkflowServiceImpl,
                         task.job.job,
                         task.task
                     )
@@ -299,7 +328,7 @@ public class StageWorkflowService(
             ServerState.TERMINATED, ServerState.ERROR -> {
                 val task = taskByServer.remove(server) ?: throw IllegalStateException()
 
-                coroutineScope.launch {
+                scope.launch {
                     server.delete()
                     server.flavor.delete()
                 }
@@ -311,7 +340,7 @@ public class StageWorkflowService(
                 activeTasks -= task
                 tracer.commit(
                     WorkflowEvent.TaskFinished(
-                        this@StageWorkflowService,
+                        this@WorkflowServiceImpl,
                         task.job.job,
                         task.task
                     )
@@ -334,7 +363,8 @@ public class StageWorkflowService(
 
                 requestCycle()
             }
-            ServerState.DELETED -> {}
+            ServerState.DELETED -> {
+            }
             else -> throw IllegalStateException()
         }
     }
@@ -345,11 +375,11 @@ public class StageWorkflowService(
         rootListener.jobFinished(job)
     }
 
-    public fun addListener(listener: StageWorkflowSchedulerListener) {
+    public fun addListener(listener: WorkflowSchedulerListener) {
         rootListener.listeners += listener
     }
 
-    public fun removeListener(listener: StageWorkflowSchedulerListener) {
+    public fun removeListener(listener: WorkflowSchedulerListener) {
         rootListener.listeners -= listener
     }
 }
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/StagePolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/StagePolicy.kt
index d76579f9..359fc223 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/StagePolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/StagePolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,9 +20,9 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage
+package org.opendc.workflow.service.scheduler
 
-import org.opendc.workflows.service.StageWorkflowService
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 import java.io.Serializable
 
 /**
@@ -32,5 +32,5 @@ public interface StagePolicy<T : Any> : Serializable {
     /**
      * Build the logic of the stage policy.
      */
-    public operator fun invoke(scheduler: StageWorkflowService): T
+    public operator fun invoke(scheduler: WorkflowServiceImpl): T
 }
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/WorkflowSchedulerMode.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/WorkflowSchedulerMode.kt
index cf8f92e0..58e7893f 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/WorkflowSchedulerMode.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/WorkflowSchedulerMode.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,11 +20,11 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service.scheduler
 
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
-import org.opendc.workflows.service.stage.StagePolicy
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * The operating mode of a workflow scheduler.
@@ -44,9 +44,9 @@ public sealed class WorkflowSchedulerMode : StagePolicy<WorkflowSchedulerMode.Lo
      * An interactive scheduler immediately triggers a new scheduling cycle when a workflow is received.
      */
     public object Interactive : WorkflowSchedulerMode() {
-        override fun invoke(scheduler: StageWorkflowService): Logic = object : Logic {
+        override fun invoke(scheduler: WorkflowServiceImpl): Logic = object : Logic {
             override fun requestCycle() {
-                scheduler.coroutineScope.launch { scheduler.schedule() }
+                scheduler.scope.launch { scheduler.schedule() }
             }
         }
 
@@ -59,14 +59,14 @@ public sealed class WorkflowSchedulerMode : StagePolicy<WorkflowSchedulerMode.Lo
     public data class Batch(val quantum: Long) : WorkflowSchedulerMode() {
         private var next: kotlinx.coroutines.Job? = null
 
-        override fun invoke(scheduler: StageWorkflowService): Logic = object : Logic {
+        override fun invoke(scheduler: WorkflowServiceImpl): Logic = object : Logic {
             override fun requestCycle() {
                 if (next == null) {
                     // In batch mode, we assume that the scheduler runs at a fixed slot every time
                     // quantum (e.g t=0, t=60, t=120). We calculate here the delay until the next scheduling slot.
                     val delay = quantum - (scheduler.clock.millis() % quantum)
 
-                    val job = scheduler.coroutineScope.launch {
+                    val job = scheduler.scope.launch {
                         delay(delay)
                         next = null
                         scheduler.schedule()
@@ -85,12 +85,12 @@ public sealed class WorkflowSchedulerMode : StagePolicy<WorkflowSchedulerMode.Lo
     public data class Random(private val random: java.util.Random = java.util.Random(123)) : WorkflowSchedulerMode() {
         private var next: kotlinx.coroutines.Job? = null
 
-        override fun invoke(scheduler: StageWorkflowService): Logic = object : Logic {
+        override fun invoke(scheduler: WorkflowServiceImpl): Logic = object : Logic {
             override fun requestCycle() {
                 if (next == null) {
                     val delay = random.nextInt(200).toLong()
 
-                    val job = scheduler.coroutineScope.launch {
+                    val job = scheduler.scope.launch {
                         delay(delay)
                         next = null
                         scheduler.schedule()
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/DurationJobOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/DurationJobOrderPolicy.kt
index 1190a408..1b5b91b9 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/DurationJobOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/DurationJobOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,21 +20,23 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.workload.Job
-import org.opendc.workflows.workload.Task
-import org.opendc.workflows.workload.WORKFLOW_TASK_DEADLINE
+import org.opendc.workflow.api.Job
+import org.opendc.workflow.api.Task
+import org.opendc.workflow.api.WORKFLOW_TASK_DEADLINE
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [JobOrderPolicy] that orders jobs based on its critical path length.
  */
 public data class DurationJobOrderPolicy(val ascending: Boolean = true) : JobOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<JobState> =
-        object : Comparator<JobState>, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<JobState> =
+        object :
+            Comparator<JobState>,
+            WorkflowSchedulerListener {
             private val results = HashMap<Job, Long>()
 
             init {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/JobAdmissionPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/JobAdmissionPolicy.kt
index 0e5a42c0..ed3acff7 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/JobAdmissionPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/JobAdmissionPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,10 +20,10 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.stage.StagePolicy
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.scheduler.StagePolicy
 
 /**
  * A policy interface for admitting [JobState]s to a scheduling cycle.
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/JobOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/JobOrderPolicy.kt
index 83d42b2d..adaa6671 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/JobOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/JobOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,10 +20,10 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.stage.StagePolicy
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.scheduler.StagePolicy
 
 /**
  * A policy interface for ordering admitted workflows in the scheduling queue.
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/LimitJobAdmissionPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/LimitJobAdmissionPolicy.kt
index 6f6ccb50..6a0bfeb9 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/LimitJobAdmissionPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/LimitJobAdmissionPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,10 +20,10 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowService
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [JobAdmissionPolicy] that limits the amount of active jobs in the system.
@@ -31,7 +31,7 @@ import org.opendc.workflows.service.StageWorkflowService
  * @property limit The maximum number of concurrent jobs in the system.
  */
 public data class LimitJobAdmissionPolicy(public val limit: Int) : JobAdmissionPolicy {
-    override fun invoke(scheduler: StageWorkflowService): JobAdmissionPolicy.Logic = object : JobAdmissionPolicy.Logic {
+    override fun invoke(scheduler: WorkflowServiceImpl): JobAdmissionPolicy.Logic = object : JobAdmissionPolicy.Logic {
         override fun invoke(
             job: JobState
         ): JobAdmissionPolicy.Advice =
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/NullJobAdmissionPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/NullJobAdmissionPolicy.kt
index ac74f090..31f8f8db 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/NullJobAdmissionPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/NullJobAdmissionPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowService
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [JobAdmissionPolicy] that admits all jobs.
  */
 public object NullJobAdmissionPolicy : JobAdmissionPolicy {
-    override fun invoke(scheduler: StageWorkflowService): JobAdmissionPolicy.Logic = object : JobAdmissionPolicy.Logic {
+    override fun invoke(scheduler: WorkflowServiceImpl): JobAdmissionPolicy.Logic = object : JobAdmissionPolicy.Logic {
         override fun invoke(job: JobState): JobAdmissionPolicy.Advice = JobAdmissionPolicy.Advice.ADMIT
     }
 
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/RandomJobOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/RandomJobOrderPolicy.kt
index 6c747261..1b359125 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/RandomJobOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/RandomJobOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,23 +20,23 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.workload.Job
+import org.opendc.workflow.api.Job
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 import java.util.*
 import kotlin.collections.HashMap
-import kotlin.collections.getValue
-import kotlin.collections.set
 
 /**
  * A [JobOrderPolicy] that randomly orders jobs.
  */
 public object RandomJobOrderPolicy : JobOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<JobState> =
-        object : Comparator<JobState>, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<JobState> =
+        object :
+            Comparator<JobState>,
+            WorkflowSchedulerListener {
             private val random = Random(123)
             private val ids = HashMap<Job, Int>()
 
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/SizeJobOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/SizeJobOrderPolicy.kt
index c1c244c3..6998606d 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/SizeJobOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/SizeJobOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowService
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [SizeJobOrderPolicy] that orders jobs based on the number of tasks it has.
  */
 public data class SizeJobOrderPolicy(public val ascending: Boolean = true) : JobOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<JobState> =
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<JobState> =
         compareBy { it.tasks.size.let { if (ascending) it else -it } }
 
     override fun toString(): String {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/SubmissionTimeJobOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/SubmissionTimeJobOrderPolicy.kt
index 005f8153..53d06023 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/job/SubmissionTimeJobOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/job/SubmissionTimeJobOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.job
+package org.opendc.workflow.service.scheduler.job
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowService
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [JobOrderPolicy] orders jobs in FIFO order.
  */
 public data class SubmissionTimeJobOrderPolicy(public val ascending: Boolean = true) : JobOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<JobState> =
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<JobState> =
         compareBy { it.submittedAt.let { if (ascending) it else -it } }
 
     override fun toString(): String {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/ActiveTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/ActiveTaskOrderPolicy.kt
index 6a465746..821d4964 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/ActiveTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/ActiveTaskOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +20,19 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskOrderPolicy] that orders tasks based on the number of active relative tasks (w.r.t. its job) in the system.
  */
 public data class ActiveTaskOrderPolicy(public val ascending: Boolean = true) : TaskOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> =
-        object : Comparator<TaskState>, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> =
+        object : Comparator<TaskState>, WorkflowSchedulerListener {
             private val active = mutableMapOf<JobState, Int>()
 
             init {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/BalancingTaskEligibilityPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/BalancingTaskEligibilityPolicy.kt
index f3f19ef5..42804f5a 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/BalancingTaskEligibilityPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/BalancingTaskEligibilityPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,12 +20,12 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 import kotlin.math.max
 
 /**
@@ -36,8 +36,8 @@ import kotlin.math.max
  * the average.
  */
 public data class BalancingTaskEligibilityPolicy(public val tolerance: Double = 1.5) : TaskEligibilityPolicy {
-    override fun invoke(scheduler: StageWorkflowService): TaskEligibilityPolicy.Logic =
-        object : TaskEligibilityPolicy.Logic, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): TaskEligibilityPolicy.Logic =
+        object : TaskEligibilityPolicy.Logic, WorkflowSchedulerListener {
             private val active = mutableMapOf<JobState, Int>()
 
             init {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/CompletionTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/CompletionTaskOrderPolicy.kt
index 0020023f..dae7ad99 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/CompletionTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/CompletionTaskOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +20,19 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskOrderPolicy] that orders tasks based on the number of completed relative tasks.
  */
 public data class CompletionTaskOrderPolicy(public val ascending: Boolean = true) : TaskOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> =
-        object : Comparator<TaskState>, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> =
+        object : Comparator<TaskState>, WorkflowSchedulerListener {
             private val finished = mutableMapOf<JobState, Int>()
 
             init {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DependenciesTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DependenciesTaskOrderPolicy.kt
index a9f5eb84..7786f6ec 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DependenciesTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DependenciesTaskOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskOrderPolicy] that orders tasks based on the number of dependency tasks it has.
  */
 public data class DependenciesTaskOrderPolicy(public val ascending: Boolean = true) : TaskOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> = compareBy<TaskState> {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> = compareBy {
         it.task.dependencies.size.let { if (ascending) it else -it }
     }
 
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DependentsTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DependentsTaskOrderPolicy.kt
index e5a9f159..4fb835d7 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DependentsTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DependentsTaskOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskOrderPolicy] that orders tasks based on the number of dependent tasks it has.
  */
 public data class DependentsTaskOrderPolicy(public val ascending: Boolean = true) : TaskOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> = compareBy<TaskState> {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> = compareBy {
         it.dependents.size.let { if (ascending) it else -it }
     }
 
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DurationHistoryTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DurationHistoryTaskOrderPolicy.kt
index 7ce8ccce..3a634de7 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DurationHistoryTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DurationHistoryTaskOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +20,19 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskOrderPolicy] that orders tasks based on the average duration of the preceding tasks in the job.
  */
 public data class DurationHistoryTaskOrderPolicy(public val ascending: Boolean = true) : TaskOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> =
-        object : Comparator<TaskState>, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> =
+        object : Comparator<TaskState>, WorkflowSchedulerListener {
             private val results = HashMap<JobState, MutableList<Long>>()
 
             init {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DurationTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DurationTaskOrderPolicy.kt
index 3674eb01..d9fde53a 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/DurationTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/DurationTaskOrderPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,15 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
-import org.opendc.workflows.workload.WORKFLOW_TASK_DEADLINE
+import org.opendc.workflow.api.WORKFLOW_TASK_DEADLINE
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 import java.util.*
 import kotlin.collections.HashMap
 import kotlin.collections.getValue
-import kotlin.collections.minusAssign
 import kotlin.collections.set
 
 /**
@@ -37,8 +36,8 @@ import kotlin.collections.set
  */
 public data class DurationTaskOrderPolicy(public val ascending: Boolean = true) : TaskOrderPolicy {
 
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> =
-        object : Comparator<TaskState>, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> =
+        object : Comparator<TaskState>, WorkflowSchedulerListener {
             private val results = HashMap<UUID, Long>()
 
             init {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/LimitPerJobTaskEligibilityPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/LimitPerJobTaskEligibilityPolicy.kt
index 2dddbc7c..229460df 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/LimitPerJobTaskEligibilityPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/LimitPerJobTaskEligibilityPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +20,19 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.JobState
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.JobState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskEligibilityPolicy] that limits the number of active tasks of a job in the system.
  */
 public data class LimitPerJobTaskEligibilityPolicy(public val limit: Int) : TaskEligibilityPolicy {
-    override fun invoke(scheduler: StageWorkflowService): TaskEligibilityPolicy.Logic =
-        object : TaskEligibilityPolicy.Logic, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): TaskEligibilityPolicy.Logic =
+        object : TaskEligibilityPolicy.Logic, WorkflowSchedulerListener {
             private val active = mutableMapOf<JobState, Int>()
 
             init {
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/LimitTaskEligibilityPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/LimitTaskEligibilityPolicy.kt
index fdc1fd5e..57aa0d58 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/LimitTaskEligibilityPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/LimitTaskEligibilityPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskEligibilityPolicy] that limits the total number of active tasks in the system.
  */
 public data class LimitTaskEligibilityPolicy(val limit: Int) : TaskEligibilityPolicy {
-    override fun invoke(scheduler: StageWorkflowService): TaskEligibilityPolicy.Logic = object : TaskEligibilityPolicy.Logic {
+    override fun invoke(scheduler: WorkflowServiceImpl): TaskEligibilityPolicy.Logic = object : TaskEligibilityPolicy.Logic {
         override fun invoke(
             task: TaskState
         ): TaskEligibilityPolicy.Advice =
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/NullTaskEligibilityPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/NullTaskEligibilityPolicy.kt
index b40f9823..cfe2aeed 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/NullTaskEligibilityPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/NullTaskEligibilityPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskEligibilityPolicy] that always allows new tasks to enter.
  */
 public object NullTaskEligibilityPolicy : TaskEligibilityPolicy {
-    override fun invoke(scheduler: StageWorkflowService): TaskEligibilityPolicy.Logic = Logic
+    override fun invoke(scheduler: WorkflowServiceImpl): TaskEligibilityPolicy.Logic = Logic
 
     private object Logic : TaskEligibilityPolicy.Logic {
         override fun invoke(
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/RandomTaskEligibilityPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/RandomTaskEligibilityPolicy.kt
index a0691b23..a01439c2 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/RandomTaskEligibilityPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/RandomTaskEligibilityPolicy.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 AtLarge Research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -20,17 +20,17 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 import java.util.*
 
 /**
  * A [TaskEligibilityPolicy] that randomly accepts tasks in the system with some [probability].
  */
 public data class RandomTaskEligibilityPolicy(val probability: Double = 0.5) : TaskEligibilityPolicy {
-    override fun invoke(scheduler: StageWorkflowService): TaskEligibilityPolicy.Logic = object : TaskEligibilityPolicy.Logic {
+    override fun invoke(scheduler: WorkflowServiceImpl): TaskEligibilityPolicy.Logic = object : TaskEligibilityPolicy.Logic {
         val random = Random(123)
 
         override fun invoke(task: TaskState): TaskEligibilityPolicy.Advice =
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/RandomTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/RandomTaskOrderPolicy.kt
index 890e7165..c12d6a66 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/RandomTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/RandomTaskOrderPolicy.kt
@@ -1,7 +1,5 @@
 /*
- * MIT License
- *
- * Copyright (c) 2019 atlarge-research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,20 +20,20 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowSchedulerListener
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
-import org.opendc.workflows.workload.Task
+import org.opendc.workflow.api.Task
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowSchedulerListener
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 import kotlin.random.Random
 
 /**
  * A [TaskOrderPolicy] that orders the tasks randomly.
  */
 public object RandomTaskOrderPolicy : TaskOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> =
-        object : Comparator<TaskState>, StageWorkflowSchedulerListener {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> =
+        object : Comparator<TaskState>, WorkflowSchedulerListener {
             private val random = Random(123)
             private val ids = HashMap<Task, Int>()
 
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/SubmissionTimeTaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/SubmissionTimeTaskOrderPolicy.kt
index 6b0199b8..e9bbf815 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/SubmissionTimeTaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/SubmissionTimeTaskOrderPolicy.kt
@@ -1,7 +1,5 @@
 /*
- * MIT License
- *
- * Copyright (c) 2020 atlarge-research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,16 +20,16 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.StageWorkflowService
-import org.opendc.workflows.service.TaskState
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
 
 /**
  * A [TaskOrderPolicy] that orders tasks based on the order of arrival in the queue.
  */
 public data class SubmissionTimeTaskOrderPolicy(public val ascending: Boolean = true) : TaskOrderPolicy {
-    override fun invoke(scheduler: StageWorkflowService): Comparator<TaskState> = compareBy<TaskState> {
+    override fun invoke(scheduler: WorkflowServiceImpl): Comparator<TaskState> = compareBy {
         it.job.submittedAt.let { if (ascending) it else -it }
     }
 
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/TaskEligibilityPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/TaskEligibilityPolicy.kt
index 37597709..ee31aee2 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/TaskEligibilityPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/TaskEligibilityPolicy.kt
@@ -1,7 +1,5 @@
 /*
- * MIT License
- *
- * Copyright (c) 2019 atlarge-research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,10 +20,10 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.TaskState
-import org.opendc.workflows.service.stage.StagePolicy
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.scheduler.StagePolicy
 
 /**
  * A policy interface for determining the eligibility of tasks in a scheduling cycle.
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/TaskOrderPolicy.kt b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/TaskOrderPolicy.kt
index 5feac6d0..fffcb765 100644
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/stage/task/TaskOrderPolicy.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/main/kotlin/org/opendc/workflow/service/scheduler/task/TaskOrderPolicy.kt
@@ -1,7 +1,5 @@
 /*
- * MIT License
- *
- * Copyright (c) 2020 atlarge-research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,10 +20,10 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service.stage.task
+package org.opendc.workflow.service.scheduler.task
 
-import org.opendc.workflows.service.TaskState
-import org.opendc.workflows.service.stage.StagePolicy
+import org.opendc.workflow.service.internal.TaskState
+import org.opendc.workflow.service.scheduler.StagePolicy
 
 /**
  * This interface represents the **T2** stage of the Reference Architecture for Topology Schedulers and provides the
diff --git a/simulator/opendc-workflows/src/test/kotlin/org/opendc/workflows/service/StageWorkflowSchedulerIntegrationTest.kt b/simulator/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/StageWorkflowSchedulerIntegrationTest.kt
index eb79162c..2161f5f2 100644
--- a/simulator/opendc-workflows/src/test/kotlin/org/opendc/workflows/service/StageWorkflowSchedulerIntegrationTest.kt
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/test/kotlin/org/opendc/workflow/service/StageWorkflowSchedulerIntegrationTest.kt
@@ -1,7 +1,5 @@
 /*
- * MIT License
- *
- * Copyright (c) 2020 atlarge-research
+ * Copyright (c) 2021 AtLarge Research
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -22,7 +20,7 @@
  * SOFTWARE.
  */
 
-package org.opendc.workflows.service
+package org.opendc.workflow.service
 
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.delay
@@ -43,16 +41,18 @@ import org.opendc.format.trace.gwf.GwfTraceReader
 import org.opendc.simulator.compute.SimSpaceSharedHypervisorProvider
 import org.opendc.simulator.utils.DelayControllerClockAdapter
 import org.opendc.trace.core.EventTracer
-import org.opendc.workflows.service.stage.job.NullJobAdmissionPolicy
-import org.opendc.workflows.service.stage.job.SubmissionTimeJobOrderPolicy
-import org.opendc.workflows.service.stage.task.NullTaskEligibilityPolicy
-import org.opendc.workflows.service.stage.task.SubmissionTimeTaskOrderPolicy
+import org.opendc.workflow.service.internal.WorkflowServiceImpl
+import org.opendc.workflow.service.scheduler.WorkflowSchedulerMode
+import org.opendc.workflow.service.scheduler.job.NullJobAdmissionPolicy
+import org.opendc.workflow.service.scheduler.job.SubmissionTimeJobOrderPolicy
+import org.opendc.workflow.service.scheduler.task.NullTaskEligibilityPolicy
+import org.opendc.workflow.service.scheduler.task.SubmissionTimeTaskOrderPolicy
 import kotlin.math.max
 
 /**
- * Integration test suite for the [StageWorkflowService].
+ * Integration test suite for the [WorkflowServiceImpl].
  */
-@DisplayName("StageWorkflowService")
+@DisplayName("WorkflowServiceImpl")
 @OptIn(ExperimentalCoroutinesApi::class)
 internal class StageWorkflowSchedulerIntegrationTest {
     /**
@@ -89,8 +89,8 @@ internal class StageWorkflowSchedulerIntegrationTest {
 
             hosts.forEach { compute.addHost(it) }
 
-            StageWorkflowService(
-                testScope,
+            WorkflowService(
+                testScope.coroutineContext,
                 clock,
                 tracer,
                 compute.newClient(),
diff --git a/simulator/opendc-workflows/src/test/resources/environment.json b/simulator/opendc-workflow/opendc-workflow-service/src/test/resources/environment.json
index 0965b250..0965b250 100644
--- a/simulator/opendc-workflows/src/test/resources/environment.json
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/test/resources/environment.json
diff --git a/simulator/opendc-workflows/src/test/resources/log4j2.xml b/simulator/opendc-workflow/opendc-workflow-service/src/test/resources/log4j2.xml
index 70a0eacc..70a0eacc 100644
--- a/simulator/opendc-workflows/src/test/resources/log4j2.xml
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/test/resources/log4j2.xml
diff --git a/simulator/opendc-workflows/src/test/resources/trace.gwf b/simulator/opendc-workflow/opendc-workflow-service/src/test/resources/trace.gwf
index d264b9c3..d264b9c3 100644
--- a/simulator/opendc-workflows/src/test/resources/trace.gwf
+++ b/simulator/opendc-workflow/opendc-workflow-service/src/test/resources/trace.gwf
diff --git a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/WorkflowService.kt b/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/WorkflowService.kt
deleted file mode 100644
index c43c72f5..00000000
--- a/simulator/opendc-workflows/src/main/kotlin/org/opendc/workflows/service/WorkflowService.kt
+++ /dev/null
@@ -1,44 +0,0 @@
-/*
- * Copyright (c) 2020 AtLarge Research
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
-
-package org.opendc.workflows.service
-
-import kotlinx.coroutines.flow.Flow
-import org.opendc.workflows.workload.Job
-import java.util.*
-
-/**
- * A service for cloud workflow management.
- *
- * The workflow scheduler is modelled after the Reference Architecture for Topology Scheduling by Andreadis et al.
- */
-public interface WorkflowService {
-    /**
-     * The events emitted by the workflow scheduler.
-     */
-    public val events: Flow<WorkflowEvent>
-
-    /**
-     * Submit the specified [Job] to the workflow service for scheduling.
-     */
-    public suspend fun submit(job: Job)
-}
diff --git a/simulator/settings.gradle.kts b/simulator/settings.gradle.kts
index 66a55c04..e87dd4d8 100644
--- a/simulator/settings.gradle.kts
+++ b/simulator/settings.gradle.kts
@@ -25,7 +25,8 @@ include(":opendc-platform")
 include(":opendc-compute:opendc-compute-api")
 include(":opendc-compute:opendc-compute-service")
 include(":opendc-compute:opendc-compute-simulator")
-include(":opendc-workflows")
+include(":opendc-workflow:opendc-workflow-api")
+include(":opendc-workflow:opendc-workflow-service")
 include(":opendc-format")
 include(":opendc-experiments:opendc-experiments-sc18")
 include(":opendc-experiments:opendc-experiments-capelin")