ENCOMPASS is an environment that suppom software development using formal techniques similar to the Vienna Development Method (VDM). In ENCOMPASS, software can be, specified using the PLEASE family of executable specification languages. PK/C++ is the latest member of the PLEASE family. PWC++ differs from its predecessor by having C++ rather than A&@ as its base language, by having an operational as well as declarative semantics, and by being based on flat rather than standard Prolog. Using PK/C++, software components are first specified using a combination of conventional programming languaga and predicate logic. These abstract components are then incrementally refined into components in an implementation language. Each re6nement is verified before another is applied; therefore, the final components produced by the development satisfy the original specifications. PWCM speci6catim may be used in proofs of correctness. They are also executable; therefore, initial specifcations can be validated and refinements can be verified using testing-based techniques. We believe the use of PK/c++ will enhance the development process. In this paper, we give an overview of ENCOM-PASS, describe P W + + in reasonable detail, and give an example of development using the language.
In a previous experiment, we demonstrated that some users seem to significantly transform the instructions for a graph creation task before the y even begin to interact with the interface, and furthermore, that this can create considerable difficulty with an interface that does not require the transformation.In this paper, we desenbe a contrasting experiment, showing that subjects without pre-existing task transformations initially have considerable difficulty with an interface that requires them, but acquire the transformations relatively quickly. Kitajima and Poison's LICAI model explains these effects as resulting from the problem representation being elaborated with task-specific schemata during the instruction comprehension process.
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