Horizontal refinements Clause Samples

Horizontal refinements. Some systems are too large and complex to have their formal modelling (the abstract model) done in just one step, and must have it done in successive steps. That is where enters the idea of horizontal refinements (or superposition). The idea consists in starting with an abstract model that only considers part of the requirements, and introducing new requirements through successive refinements, adding new variables, strengthening pre-conditions, adding invariants, actions or operations. 110 ▇▇▇▇▇▇ ▇ ▇▇▇▇▇ ▇▇ The person doing the modelling process has to explore the requirements docu- ment (in the methodology presented in this paper, the WRSPM model) and gradually take from it the elements to be formalized, taking care to correctly define the archi- tecture that supports the incremental addition of information and to define a good order to add this requirements, so abstraction disparities are not faced (like a very concrete requirement being added in a highly abstract level). Another issue is to guarantee completeness with the previous model (WRSPM): the horizontal refine- ments process must last until all the requirements and definitions have been taken into account, and only when this is complete, can the designer start the process of vertical refinements, pushing the model into more concrete levels through design decisions until a level concrete enough to generate code is reached.