information:classification, structural:reformatting, linguistic:translation, information:extraction
Operational semantics

In the spirit of imperative programming, an abstract data structure is conceived as an entity that is mutable — meaning that there is a notion of time and the ADT may be in different states at different times. Operations then change the state of the ADT over time; therefore, the order in which operations are evaluated is important, and the same operation on the same entities may have different effects if executed at different times. This is analogous to the instructions of a computer or the commands and procedures of an imperative language. To underscore this view, it is customary to say that the operations are executed or applied, rather than evaluated, similar to the imperative style often used when describing abstract algorithms. The constraints are typically specified in prose.