Based on the ArchiMate 3 documents or objectives, an aggregation relationship indicates that an
element groups a number of other concepts. The aggregation relationship has been inspired by the
aggregation relationship in UML class diagrams. Unlike composition, aggregation does not imply an
existence dependency between the aggregating and aggregated concepts. The notation for an
aggregation relationship is a solid line with an empty diamond at the end that points to the whole
element. The diagram uses an aggregation relationship from the bottom elements to the top
element to indicate that the top element groups the bottom elements.
Reference: ArchiMate® 3.2 Specification, Chapter 5 Relationships, Section 5.1 Structural
Relationships 1; Structural Relationship: Part 3 - ArchiMate Resources for FREE 2.