Experiences in using b and UML in industrial development
B'07 Proceedings of the 7th international conference on Formal Specification and Development in B
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Simple retrenchment is briefly reviewed in the B specification language of J.-R. Abrial [1] as a liberalization of classical refinement, for the formal description of applicationdevelopments too demanding for refinement. Thelooser relationships allowed by retrenchment between adjacentmodels in the development process may capture someof the requirements information of the development. Thiscan make requirements validation more difficult to understandsince the locus of requirements should be the models,and not their interrelationships, as far as possible. Hencethe universal construction of [6], originally proposed forsimple transition systems, is reformulated in B, in orderto "lift" a given retrenchment conceptually, thus retractingsuch requirements information back to the level of abstractionof the abstract, ideal model. Examples demonstratethe cognitive value of retracting requirements to theabstract level, articulated in a well-understood formal language.This is also seen to yield a more understandable wayof comparing alternative retrenchment designs. Some new Bsyntax in the pre- and postcondition style is presented to facilitateexpression of the lifted requirements.