- language family for all (?) aspects of TM engineering
- set of notations for authoring, constraining, querying and updating
- languages depend on each other
- same or similar syntax
- common set of paradigms and common formal foundation
- transition paths for knowledge engineers
- combining languages is possible, build larger infrastructures
- balanced expressiveness: expressive enough for most tasks, but not too expressive to remain computational tractable in larger contexts
- this allows for cross-fertilization and global optimization
