Stronger compositions for retrenchments

Output Retrenchments , Defaults , Stronger Compositions , Feature Engineering

Output retrenchment, a type of retrenchment in which when the retrieve relation is reestablished for an after-state, it is strengthened by a relation on outputs, is introduced and studied. The output relation balances syntactically the statements that can be made about the 'successful transitions', as against the statements that can be made about the transitions that merely establish the conced...

Composition mechanisms for retrenchment

Retrenchment is a flexible model evolution formalism that arose as a reaction to the limitations imposed by refinement, and for which the proof obligations feature additional predicates for accommodating design data. Composition mechanisms for retrenchment are studied. Vertical, horizontal, dataflow, parallel and fusion compositions are described. Of particular note are the means by which the a...

Structuring Retrenchments in the small with B

Simple retrenchment is briefly reviewed as a liberalisation of classical refinement, for the formal description of application developments too demanding for refinement. Two generalisations, output and evolving retrenchment, are presented. Simple monotonicity results for retrenchment are recalled, forming the basis of a piecewise development method. This work then commences the study of the str...

Composing and Promoting Retrenchments in Z

We briefly review the the compositional mechanisms of Z, i.e. the schema calculus and promotion. Retrenchment, a generalization of classical data refinement, is reviewed in a Z setting. Experience applying retrenchment to the Mondex Electronic Purse specification [16, 8] – which used promotion in combination with refinement – has established that promotion is a useful tool in the requirements e...

The Mondex Purse: Requirements and Retrenchments