An  Aggregate Member is an Entity that serves as an internal constituent of an Aggregate Block, incorporating (aggregating) an external Building Block into its parent structure.

Aggregation is the syntactic mechanism that enables the construction of modular, composite Building Blocks. It establishes a reified Relationship (the nested   Aggregate Member) between the Aggregate Block and the aggregated Building Block, allowing the definition of local characteristic specific to the  Aggregate Member. This mechanism facilitates the expression of emergent properties within the composite structure of  the Aggregate Block .

Examples:

. "Attributes" of a "UML class" are   Aggregate Members.

. Steps of a process are   Aggregate Members.

. "Specializations" of a Class are   Aggregate Members.

A  Building Block is an autonomous Entity that contributes to the makeup of other  Building Blocks.

 Building Blocks can be either reusable entities (packaged in Containers) or be local to the Aggregate Block that references them (see Block Lexical Scope and Hierarchical Member).

Examples:

-  Functionality(ies), Business Process(es), Data Entity(ies), Tags, ARE  Building Blocks.

- Process Steps or  Attributes of a data entity ARE NOT  Building Blocks. They are members on an internal structure (see Aggregate Member).