"Java-based Open Source WF Verification and WFMS. A set of modules for running verifiably correct workflows diagrammed using UMLv2.0"
Contents
Introduction
Workflows
Diagramming
Verification
Software
Downloads
Papers
Links
Contact
There are many definitions of workflows often with an implicit perception that the type
of workflow is understood.
These definitions will be considered and an outline of the approach used for this particular
system will be given. Note that it will be UML based as this is now a de facto standard
comprehensible to non-technical users.
[20 Aug 2004]
A comprehensive view and the process of constructing workflows using UMLv2.0
Behavio(u)rs will be posted during the
course of the next few weeks and months.
The intention is to have an open source Java based system that:
[21 Aug 2004]
A little restructuring and correction made to this page. Some additional information added.
A discussion regarding:
Some discussion wrt characteristics of all workflows will be given.
A brief outline of diagramming for Petri nets and a more comprehensive outline of
UMLv2.0 Activity diagrams. Discussion wrt to anomalies, ambiguities, omissions,
unnecessary syntactic sugaring and so on.
For example, some systems consider the diagram on the right to be incorrect ...
(Is it?)
Comprehensive discussion outlining how UMLv2.0 Activity diagrams may be rigourously
verified. Points covered include:
Syntactical validation
The syntax of a workflow is formally defined from the results of graph theory.
Syntactical validation checks component usage of the diagram, such as:
Structural validation
Some structural components are not covered in syntactical validation, for example:
critical tasks or processes.
Restrictions
Restrictions include not allowing some constructs that are just syntactic sugaring.
For example, Conditional Nodes are defined in the UMLv2.0 spec. as: "… a structured
activity node that represents an exclusive choice among some number of alternatives."
This can be represented as a set of Actions with Decision Points having guard transitions.
Hence Conditional Nodes will be rejected.
Other
Validations are made for:
If an activity is not reachable from any start activity of a process definition,
the activity will have no chance to be executed. Therefore, it makes no sense to
define such an activity in a process definition.
Does the workflow model the wishes of the user correctly? The semantics of a
workflow structure is the set of possible traces through the structure, that is
all possible action sequences. A complete set of instance subgraphs of a workflow
graph would be validated.
It may so arise that in some workflows, specific tasks or processes must be invoked.
This notion is tied up with the idea of Reachability.
A sequence of events exists leading to the execution of a workflow object.
Resources required by the workflow of the system to operate correctly. This will be
based on a security/role based sub-system.
Partitions (Resources/Swimlanes)
Implies the workflow is not dead. That is, there exists an initial state such that
the workflow will start and that movement between processes of the workflow keep the
workflow in a correct state.
The workflow must be able to finish and, on termination, there should be no dead
tasks. This is usually as a result of a terminating decision. It should be
possible to execute an arbitrary task by following the appropriate route though
the workflow. No state should occur more than a limited number of times.
Where the semantics cannot be verified (perhaps because conditions are calculated
within a process not exposed to the workflow), where a condition occurs which cannot
be routed or handled by the WfMS, an exception occurs.
Design of the system using Aspect Oriented Programming (AOP) methods. Brief outline of AOP and thread synchronization in JDK1.5. (Every Activity is a thread and every Action within an Activity is run as a separate thread).
A JAR download.
Various standards, white papers and links to (mainly academic) papers.
UMLv2.0 Superstructure [current status: Final, but not complete release]
XML Metadata Interchange [XMI]
Links to useful sites such as:
UML org
OMG org
WfMC org
A list of other Workflow systems can be found in
manageability.org.
Note, not all are open source, they quite often use proprietary diagramming
methods or use languages (mainly XML based) and none (so far as I am aware) verify
their diagrams comprehensively.
Serious enquiries regarding workflows and modeling workflows in UMLv2.0 can currently be addressed to: Workflow Enquiry. Note that flippant enquiries will be studiously ignored.
Activity with Parameters
Loop