Desirable Characteristics of a Requirements Specification
Abstract (one model, many realizations)
Complete (to the extent required)
Consistent (no contradictions)
Unambiguous (any system that satisfies it is acceptable)
Precise (uniquely interpretable)
Feasible (can be satisfied within constraints)
Even (entire document at same level of detail)
Modifiable (living document)
Reference Tool (readable by customer, developer, maintainer)