Block Checks

The third set of structural validations carried out are block checks. These ensure ensuring that the flow graph is correctly block-structured.

The block-start constructs are: Start Process Activity, Loop Begin Activity, Parallel (AND) Split and Choice (XOR) Split. Their corresponding block-end constructs are: End Process Activity, Loop End Activity, Parallel (AND) Join and Choice (XOR) Join.

Based on these, the following block-structure validations are executed:

• For every block start, there must be a corresponding block end (i.e. if there is a Loop Begin activity in the workflow, then there must be a corresponding Loop End activity).
• The block start/end types must match (i.e. if there is a Parallel (AND) Split present in the workflow graph, then this must be matched by a corresponding Parallel (AND) Join).
• Blocks can be nested but not interleaved.