Principle 19

"The conversion from an intuition to a theory involved understanding:

(1) the software structure (which included a representation packaged with its primitive operators),

(2) specifications (mathematically expressed as abstract models or algebraic axioms),

(3)  language issues (modules, scope, user-defined types),

(4) integrity of the result (invariants of data structures and protection from other manipulation),

(5) rules for combining types (declarations),

(6) information hiding (protection of properties not explicitly included in specifications)."

(David Garlan, Mary Shaw. An Introduction to Software Architecture, 1994)