initial import of WPI-{data,control}+CWL analysis

README.md

@@ -13,7 +13,7 @@ _Some patterns commonly encountered when writing CWL workflows_
 - [Manipulating a list of files using expressions](#manipulating-a-list-of-files-using-expressions)
 - [Link input files to working directory](#link-input-files-to-working-directory)
 - [How to handle port type mismatches](#how-to-handle-port-type-mismatches)
-
+- [Which of the Workflow Patterns Initiative patterns does CWL support?](workflow_patterns_initiative/README.md)
 <!-- /TOC -->
 
 ## Manifest file via Javascript

workflow_patterns_initiative/README.md

@@ -0,0 +1,18 @@
+http://www.workflowpatterns.com/
+
+Each sub-folder analyzes the features of CWL against a category of patterns found in the Workflow Patterns Initiative's website.
+
+- [Control](control/README.md) patterns
+- Resource patterns
+- [Data](data/README.md) patterns
+- Exception Handling patterns
+- Presentation patterns
+- Event Log Imperfection patterns
+
+
+Note: the WPI's definition of a workflow is much broader than the type of workflows CWL aims to describe.
+
+CWL targets workflows made of command line tools with no real-time communication between steps nor outside services.
+WPI's definition of workflows includes (business) process modeling which have many control-flow features.
+
+Therefore these are not to be treated as "to do" lists for CWL, but a way to describ and demonstrate CWL's features and abilities in the larger workflow space.

workflow_patterns_initiative/control/README.md

@@ -0,0 +1,254 @@
+
+# WPI's [Workflow Control Patterns](http://www.workflowpatterns.com/patterns/control/) and CWL
+
+Note: CWL is a data-driven (dataflow) workflow standard. These patterns use control-flow language and thus we speak of the equivalent data-flow constructs.
+There is no concept of "thread of control" in CWL.
+
+Of the 43 WPI Workflow Control patterns, 8 patterns are supported by CWL v1.2 or earlier and 35 patterns are unsupported.
+
+[Back to the list of WPI pattern categories](../README.md)
+
+## "Basic Control Flow Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/basic/wcp1.php">Pattern 1 (Sequence)</a>
+
+Yes. CWL is a DAG based workflow language with explicit dependencies between steps.
+
+CWL versions: all
+
+* <a href="http://www.workflowpatterns.com/patterns/control/basic/wcp2.php">Pattern 2 (Parallel Split)</a>
+
+Yes. Anytime a step in a CWL workflow has all of its inputs available it is allowed to be executed.
+
+CWL versions: all
+
+* <a href="http://www.workflowpatterns.com/patterns/control/basic/wcp3.php">Pattern 3 (Synchronization)</a>
+
+Yes. One can have a step in a CWL workflow that requires inputs from the result of multiple other steps.
+Downstream steps that require the output of that step (and their descendents) will not be available for execution until the combination step has finished.
+
+CWL versions: all
+
+* <a href="http://www.workflowpatterns.com/patterns/control/basic/wcp4.php">Pattern 4 (Exclusive choice)</a>
+
+Yes. No explicit construct, but can be achieved by marking the two downstream steps with the `when` CWL conditional step
+execution feature where the logic for one step's `when` field is the inverse of the other step's `when` field.
+
+If there is a downstream workflow step that would inherit an value from one of the exclusive choice steps into the same incoming input port, then `pickValue: the_only_non_null` may be helpful to ensure that both "exclusive" choices didn't execute due to a misconfiguration in their `when` logics.
+
+CWL versions: v1.2+
+
+* <a href="http://www.workflowpatterns.com/patterns/control/basic/wcp5.php">Pattern 5 (Simple Merge)</a>
+
+Yes. Any workflow can include another workflow as a step, thus allowing re-use.
+
+CWL versions: all
+
+## "Advanced Branching and Synchronization Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/advanced_branching/wcp6.php">Pattern 6 (Multi-Choice)</a>
+
+No, as there is not a construct in CWL to implement this directly, as required by the WPI definition of this pattern.
+Can be emulated using the CWL v1.2 `when` similar to the method to implement Pattern 4 (Exclusive choice), but with 3 or more steps using matched `when` markers
+
+* <a href="http://www.workflowpatterns.com/patterns/control/advanced_branching/wcp7.php">Pattern 7 (Structured Synchronizing Merge)</a>
+
+No, as there is not a construct in CWL to implement this directly, as required by the WPI definition of this pattern.
+One way to achieve this is to hide the choice inside a sub-workflow which will provide a stable set of outputs to connect to other steps.
+As this pattern implies the conditional execution of prior steps, the use of the `pickValue` construct in the merge step will likely be useful.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/advanced_branching/wcp8.php">Pattern 8 (Multi-Merge)</a>
+
+No, as CWL does not have a construct for the WPI Multi-Choice pattern, which is a pre-requisite for the WPI definition of the Multi-Merge pattern.
+
+However, any CWL step can rely on inputs from multiple other steps. This functionality is available in all CWL versions.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/advanced_branching/wcp9.php">Pattern 9 (Structured Discriminator)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp28.php">Pattern 28 (Blocking Discriminator)</a>
+
+No. State in CWL is read-only, therefore this pattern is not supported as it would be impossible to reset the discriminator.
+This pattern is likely not possible in CWL for other reasons as well.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp29.php">Pattern 29 (Cancelling Discriminator)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+Additionally, all variables in CWL are read-only so there is no ability to "reset [a] construct".
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp30.php">Pattern 30 (Structured Partial Join)</a>
+
+No. CWL does not support canceling the execution of tasks according to some dynamic criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp31.php">Pattern 31 (Blocking Partial Join)</a>
+
+No. CWL does not support re-ordering of tasks.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp32.php">Pattern 32 (Cancelling Partial Join)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp33.php">Pattern 33 (Generalized AND-Join)</a>
+
+No. CWL is a dataflow workflow language, not a control-flow workflow language. All inputs must be known at the time of workflow enactment.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp37.php">Pattern 37 (Local Synchronizing Merge)</a>
+
+No. CWL is a dataflow workflow language, not a control-flow workflow language.
+
+A CWL step can not accumulate inputs (or continue to emit outputs) over time.
+CWL steps are only executed once (unless `scatter` is used) and the results of that step are only made available once execution has finished.
+
+See also the evaluation of CWL against Pattern 7 (Structured Synchronizing Merge).
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp38.php">Pattern 38 (General Synchronizing Merge)</a>
+
+Yes, as this was easy to implement due to two factors related to CWL being a dataflow workflow language and not a control-flow workflow language:
+
+1. CWL steps are only executed once (unless `scatter` is used) and the results of that step are only made available once execution has finished.
+
+2. A CWL step is available for execution when all of the upstream steps have been executed (or permanently skipped due to the use of the `when` construct).
+
+CWL versions:
+  without conditional steps: all
+  with contional steps: v1.2+ 
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp41.php">Pattern 41 (Thread Merge)</a>
+
+No, CWL has no concept of threads at the workflow language level. The underlying applications may use POSIX threads, but that is not managed by CWL.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp42.php">Pattern 42 (Thread Split)</a>
+
+No, CWL has no concept of threads at the workflow language level. The underlying applications may use POSIX threads, but that is not managed by CWL.
+
+## "Multiple Instance Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/multiple_instance/wcp12.php">Pattern 12 (Multiple Instances without Synchronization)</a>
+
+No. While CWL has the `scatter` construct, using this implies an implicit "gather"ing of the results before downstreams steps can use the results.
+This means that execution of subsequent steps is delayed for the slowest execution of the the `scatter`ed tasks, even if that particular result isn't needed right away.
+
+Additionally, CWL does not have a `loop` construct, which would be another way one could implement this pattern.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/multiple_instance/wcp13.php">Pattern 13 (Multiple Instances with a priori Design-Time Knowledge)</a>
+
+No. There is no CWL construct to execute a step or task a specific N number of times, where N is a concrete number (like 23) specified by the workflow author.
+
+Additionally, CWL does not have a `loop` construct, which would be another way one could implement this pattern.
+
+However: this pattern could be emulated in a CWL editor or language that converts to CWL syntax by creating explicit steps (23 in our example) in the CWL workflow description.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/multiple_instance/wcp14.php">Pattern 14 (Multiple Instances with a priori Run-Time Knowledge)</a>
+
+Yes. CWL has the `scatter` construct which allows a compact directive that a given step is to be executed multiple times where most inputs are fixed except for those `scatter`ed specified inputs.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/multiple_instance/wcp15.php">Pattern 15 (Multiple Instances without a priori Run-Time Knowledge)</a>
+
+No. CWL lacks any construct that can spawn additional tasks dynamically according to criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp34.php">Pattern 34 (Static Partial Join for Multiple Instances)</a>
+
+No. CWL does not have the ability to allow execution of a downstream step when N of M tasks have completed.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp35.php">Pattern 35 (Cancelling Partial Join for Multiple Instances)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp36.php">Pattern 36 (Dynamic Partial Join for Multiple Instances)</a>
+
+No. CWL lacks any construct that can spawn additional tasks dynamically according to criteria.
+
+## "State-based Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/state/wcp16.php">Pattern 16 (Deferred Choice)</a>
+
+No. The CWL v1.2+ conditional workflow step ability is only based upon explict inputs to the workflow step.
+
+Additionally, in CWL there is no concept of an "operating environment".
+
+* <a href="http://www.workflowpatterns.com/patterns/control/state/wcp17.php">Pattern 17 (Interleaved Parallel Routing)</a>
+
+No. Ordering of tasks in CWL is not fixed, but the dependecy graph is explicit.
+
+There is no CWl construct to limit the number of parallel tasks being executed, that is up to the workflow engine.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/state/wcp18.php">Pattern 18 (Milestone)</a>
+
+No. In CWL, parameter values are read-only; they can not change over time.
+
+It is not possible to query the state of another CWL task.
+
+A step in a CWL workflow can only recieve specific outputs from other steps that have already completed, and this wiring is fixed prior to workflow execution.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp39.php">Pattern 39 (Critical Section)</a>
+
+No. Sub sections of CWL workflows can not be bidirectionally connected. One could depend on another (by putting the other in a sub-workflow, if it isn't one already).
+
+It is not possible to query the state of another CWL task.
+
+A step in a CWL workflow can only recieve specific outputs from other steps that have already completed, and this wiring is fixed prior to workflow execution.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp40.php">Pattern 40 (Interleaved Routing)</a>
+
+No. Ordering of tasks in CWL is not fixed, but the dependecy graph is explicit.
+
+There is no CWl construct to limit the number of parallel tasks being executed, that is up to the workflow engine.
+
+## "Cancellation and Force Completion Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/cancellation/wcp19.php">Pattern 19 (Cancel Task)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/cancellation/wcp20.php">Pattern 20 (Cancel Case)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+Additionally, CWL does not have the concept of a "case".
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp25.php">Pattern 25 (Cancel Region)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp26.php">Pattern 26 (Cancel Multiple Instance Task)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp27.php">Pattern 27 (Complete Multiple Instance Task)</a>
+
+No. CWL does not support canceling the execution of tasks according to some criteria.
+
+## "Iteration Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/structural/wcp10.php">Pattern 10 (Arbitrary Cycles)</a>
+
+No. CWL has no loop construct.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp21.php">Pattern 21 (Structured Loop)</a>
+
+No. CWL has no loop construct.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp22.php">Pattern 22 (Recursion)</a>
+
+No. CWL does not support recursion.
+
+## "Termination Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/structural/wcp11.php">Pattern 11 (Implicit Termination)</a>
+
+Yes. CWL workflows are finished when all of the required outputs are available.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp43.php">Pattern 43 (Explicit Termination)</a>
+
+No. CWL does not have an explicit "end node" construct.
+
+## "Trigger Patterns"
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp23.php">Pattern 23 (Transient Trigger)</a>
+
+No. CWL does not support the concept of triggers or signals.
+
+* <a href="http://www.workflowpatterns.com/patterns/control/new/wcp24.php">Pattern 24 (Persistent Trigger)</a>
+
+No. CWL does not support the concept of triggers or signals.