In short: instead of repeating recurring building-block substructures, factor those out into a crosscutting concepts.

Troublesome redundancy

See the following building block diagrams: The top-level (whitebox X) consists of blackboxes A, B and D - which are refined in three diagrams.

All those refinements look strikingly similar - that’s too much redundancy.

Crosscutting Concepts to the rescue

A somewhat leaner approach, based upon crosscutting concepts, avoids this redundancy. In the following diagram, the whitebox contains blackboxes A, B and D - but there’s no refinement for those. Instead, they all carry the stereotype «X-service», refering to a crosscutting concept that explains how elements of type X-service» shall be constructed, build or implemented.

Crosscutting concepts might describe principles, rules or implementation restrictions that must hold for specific kinds of building blocks. See section 8 for details.