The TieFlow Workflow Toolkit is a web-based electronic workflow system
used to automate manual, form-based processes. These processes are
specified in XML according to a DTD created for the workflow engine.
The TieFlow Workflow Toolkit has a Java graphical Workflow Editor
to allow users to graphically create, display, and modify process
definitions. The Workflow Editor converts the graphical representation
of the process and its underlying data (entered by the process creator
in the Workflow Editor as part of the process definition) into an
XML document according to the workflow process DTD. This XML document
is then imported into the Workflow Engine for execution.
While the XML process definition is automatically validated according
to the DTD, the DTD validation does not identify incomplete or incorrect
process definitions. The current process verifier uses a graph reduction
strategy to determine the validity of the process flow. While this
works well for simple, top-down processes, it does not work for
processes containing loops. As a result, it cannot be used for nearly
all of the processes developed with the
Workflow Toolkit. Additionally, the current verifier is a stand-alone
program with a rudimentary user interface.
The objective of this project is to modify the current verification
strategy or implement a new verification strategy to handle loops
in the process and any/all other valid process flows. Also, the process
verifier must be integrated as a capability within the Workflow Editor.
Finally, the user interface displaying the verification results (warnings
and errors) should be improved and integrated with the editor's graphical
Code / Architecture
1. Process Verifier shall be integrated and compatible with the TieFlow
Workflow Toolkit Workflow Editor.
2. Process Verifier shall use the Java JDK version 1.5 for any required
3. Process Verifier shall use the XML parser currently used by the
Workflow Editor for any required XML processing.
4. Process Verifier shall provide the capability for the user to select
the process definition desired for verification. By default, it should
be the process definition currently selected and displayed in the
5. Process Verifier shall automatically include any and all sub-processes
associated with the selected process definition.
6. Process Verifier shall analyze the process definition to find errors,
inconsistencies, and logical problems in the process definition. Ideally,
the "rules" would be configurable to allow addition or modification
of individual rules without redesign or major modification of the
7. Process Verifier shall provide multiple error types to indicate
the severity of the violation. At a minimum, the types should include:
8. Process Verifier shall verify the following Error rules:
- Error: indicates a definite violation that would prevent the
proper execution of the process.
- Warning: indicates unusual circumstances that will not cause a
problem in the execution of the process for the workflow engine,
but may not be the process creator's intent.
9. Process Verifier shall verify the following Warning rules:
- A process definition must contain at least one activity.
- A process definition must contain one and only one ProcessStart.
- A process definition ProcessStart must have at least one EntryPoint.
- Each Transition to an EntryPoint of a ProcessStart cannot share
the EntryPoint with any other Transition. (No AND-join in a ProcessStart
or no AND-join to a subProcess)
- A process definition ProcessStart must have at least one ExitPoint.
- A process definition must contain one and only one ProcessEnd.
- A process definition ProcessEnd must have one and only one
ExitPoint. (No AND-split from a subProcess)
- The Transition from the ExitPoint of a ProcessEnd cannot share
an Entry Point with any other Transition. (No AND-join from a
ProcessEnd or a subProcess cannot go to an AND-join)
- A process definition ProcessEnd must have at least one EntryPoint.
- Each AssigneeRole maximum attribute value must be greater than
or equal to its minimum attribute value unless the maximum attribute
value is 0.
- AssigneeRole maximum attribute must be integer values greater
than or equal to 0.
- AssigneeRole minimum attribute must be integer values greater
than or equal to 1.
- Each Activity must have at least one EntryPoint.
- Each Activity must have at least one ExitPoint with a specified
- Each Activity must have at least one transition to one of its
EntryPoints from an ExitPoint of another Activity, ProcessStart,
- Each Transition must specify one and only one ExitPoint as
its origin and one and only one EntryPoint as its destination.
- For every split in the process flow where multiple threads
of control execute in parallel (AND-split), there must be a corresponding
join where each of those parallel threads recombine into a single
process thread (AND-join). The individual parallel threads are
required to either terminate in a dead-end or rejoin the other
parallel threads. However, the parallel threads are not required
to all recombine at the same time and place. The only requirement
is that they recombine or terminate before the end of the process.
- Transitions from Activities within a split parallel thread
must connect to the EntryPoint of Activities or SubProcesses within
the split parallel thread or to the EntryPoint of an Activity
that is combining with one or more of the other split parallel
threads (AND-join). Likewise, transitions to Activities within
a split parallel thread must originate from the ExitPoint of Activities
or SubProcesses within the split parallel thread or from the ExitPoint
of the Activity where split parallel threads originated (AND-split).
In other words, no Transitions may be made into or out of the
Activities within the split parallel threads section of a process,
unless the Transitions are completely contained within the split
parallel threads section of the process.
- Every independently executable path through a process must
start at the WorkflowStart and end at the WorkflowEnd. In other
words, a process cannot have paths without an end. In the case
of an AND-split, an individual split parallel path may deadend
as long as at least one of the other split parallel paths continues
to the end of the process. In the case where a process has optional
paths (OR-split), each optional path must be complete from one
end of the process to the other.
10. Process Verifier shall verify the following valid process
- Each Activity must have at least one Transition from one of
its ExitPoints to the EntryPoint of another Activity, ProcessEnd,
SubProcess, or ProcessGround.
- RoleID of an AssigneeRole specified in an Activity must be
defined in the process definition document by a Role.
- Each SIMPLE Activity must have at least one AssigneeRole.
- AUTOMATIC Activities cannot have an AssigneeRole.
- Each SIMPLE Activity must have at least one ExitPoint with
label. In other words, the Activity must have at least one visible
- Each SIMPLE Activity must have a single formLayout.
- linear (one Transition from an ExitPoint to an EntryPoint)
- OR-split (process object has multiple Transitions each from
their own ExitPoint)
- OR-join (process object has multiple Transitions each to their
- AND-split (process object has multiple Transitions from a single
- AND-join (process object has multiple Transitions to a single
- loopback (Transition goes from a process object to itself or
a previous process object)
- dead-end (process object has a Transition to the ProcessGround)
Process Verification Results
11. Process Verifier shall display some indication of status while
it is executing.
12. Process Verifier shall display the verification results in a new
13. Process Verifier shall display each error found.
14. Process Verifier shall display errors of the same type grouped
together with the error type displayed only once, followed by the
details of each violation.
15. Process Verifier shall display the possible cause of or corrective
action for each error.
16. Process Verifier shall display each warning found.
17. Process Verifier shall display warnings of the same type grouped
together with the warning type displayed only once, followed by the
details of each violation.
18. Process Verifier shall display the possible cause of or correction
action for each warning.
19. Process Verifier shall highlight the error/warning area of the
process in the graphical display when an individual error or warning
is clicked in the Verification Results window.