Participation
Optional participation means a minimum of zero related instances; mandatory participation means a minimum of one. Name whose participation you are describing.
Worked example: CUSTOMER:ORDER
A customer may have 0..many orders, so CUSTOMER participation in ORDER is optional. Each order belongs to 1..1 customer, so ORDER participation in CUSTOMER is mandatory.
Six classifications
For both directions of each pair, give the related-instance count and classify participation as mandatory or optional. Explain each answer using these Stories on CD assumptions:
- ORDER:LINE ITEM: Each submitted order has one or more lines; each line belongs to exactly one order. Draft orders are outside this model.
- LINE ITEM:CD: Each line names exactly one CD title; each CD title may occur on zero or many order lines.
- CD:DISTRIBUTOR: Each CD title has exactly one distributor; a distributor may supply zero or many CD titles in this simplified case.
Write, for example, “One CUSTOMER has 0..many ORDER instances; CUSTOMER participation is optional.” Use explicit counts rather than assuming solid or dashed lines have a universal meaning.
Self-assessment: 30 points
Award up to 5 points for each of the six directions: 2 for participation, 2 for minimum/maximum counts, and 1 for a matching business-rule explanation. Total: 30 points. The page displays a model answer; it does not automatically grade free text.