System families
Object and class behavior; identity; messaging; execution; scheduling; storage; workspaces; naming and discovery; networks; devices; graphics; input; security; provenance; versioning; and deployment.
Domain families
Software development
Source models, syntax, compilation, testing, debugging, dependency resolution, revision history, packaging, and realization.
Technical writing
Structured documents, references, citations, revisions, annotations, collaborative review, and publication.
Desktop publishing
Typography, layout, pagination, color management, preflight, and production output.
Graphic design
Vector and raster models, layers, transformations, brushes, filters, and asset management.
Video
Timelines, clips, effects, media sources, codecs, synchronization, compositing, and rendering.
Overlap is the point
Revision history, search, annotation, provenance, collaboration, rendering, transformations, and publication recur across domains. A protocol family should be factored where meaning is genuinely shared, allowing different tools and activities to reuse it without collapsing their distinctions.