The Workflow Engine creates a Task whenever a manual activity is executed. At the time that the Task is created, the Workflow Engine takes a snapshot of any Workflow Data Object values that are used by the Task (for example, used in the Task Subject, or Primary Action). This snapshot is stored as XML data in the wdoSnapshot attribute of the Task entity. If the XML string exceeds 3900 characters, it is broken up into a sequence of strings, each with a maximum length of 3900 characters. These strings are then stored as overflow records.

When the Workflow Engine attempts to reconstruct the Task's wdoSnapshot, it reads the wdoSnapshot from the Task record and appends any associated overflow records.

Example

You define a workflow (Process Definition) to allow correspondence to be sent to customers whenever their payment details change. The activities defined in your workflow are:

• system prints out a letter (automatic); and
• User puts the letter in an envelope and posts it (manual).

Person John Smith's payment details change due to an increase in rates. This increase raises an event which causes the Workflow Engine to enact your workflow and create a Process Instance.

The system creates and executes the first (automatic) Activity Instance which prints out the letter.

The system transitions to the next activity definition in your workflow and creates the second Activity Instance. Because this Activity Instance is a manual one, when the Workflow Engine executes the Activity Instance, it also creates a Task which details the work to be done (as defined by the activity in your Process Definition).

The Manual Activity maps data from several Workflow Data Objects to the Task. The system captures these data values and snapshots them in an XML string. The string is 8,000 characters long. The system breaks this string up into two blocks of 3900 characters and one of 200 characters. It persists the first block in the Task entity's wdoSnapshot attribute. It then persists the second and third block as sequential overflow records.

The User to whom the Task was assigned opens their Inbox, which causes the Inbox to request the Task Subject from the Workflow infrastructure. The infrastructure acquires the initial wdoSnapshot from the Task record and appends the two overflow records in sequence. This re-forms the original XML document, thereby allowing the Workflow Engine to construct & return the Task Subject.

Technical Notes

See the Workflow Reference Guide for further information.