PPMN_ — Occurrence Aggregation

Occurrences need the ability to aggregate Occurrences sub-Occurrences without having them necessarily be in a sub-chain. This supports the tying together of different types of Occurrences such as a Custody Occurrence and a Pedigree Occurrence. An example is the loading of grain from a farm into a shipping truck that already has grain in it. This is a combination of the grain as well as custody of the grain passing from the farm or depot to the shipping company.

Modify OccurrenceRelationship and OccurrenceRelationshipType to include Composition

OccurrenceRelationship and OccurrenceRelationshipType are specializations of ElementRelationship and ElementRelationshipType, respectively. They are currently used to signify sequencing relationships between Occurrences. These elements could also be used to aggregate Occurrences as suggested by the issue. It would mean removing or changing how the predecessor relationship is calculated. This proposal suggests reusing "Transition" instance of RelationshipKind (from SCE) to represent "predecessor" occurrences. The predecessor property of Occurrence has therefore been updated to a derived property that will be calculated based on OccurrenceRelationships with kind set to Transition to account for that requirement. This also allows the use of other relationship kinds, especially "Composition" which would address the issue.