A Framework for implementing Web Scheme Transformers By - Example

Transformers By-Example (TBE) is a concept that facilitates the definition and application of scheme transformers. When defining a conceptual scheme modelers can use scheme transformers, which transform an input scheme into an extended or refined output scheme, for automatically performing modelling tasks. An exemplary modelling task in the sphere of web application modelling is "after having defined an entity type, add a page class for displaying the entity type's content". In TBE, a transformer is defined graphically by giving a generic example of an input scheme and an output scheme, i.e. a scheme before and after the transformation, respectively. Therefore, modelers define transformers in a notation that is similar to one which they are familiar with. The scheme modification operations necessary for performing transformations of schemes are derived from the graphical specification. This is in contrast to other approaches for scheme transformers where modelers have to specify such operations based on some internal representation of schemes, e.g. a representation in XML. A TBE-system, i.e. the implementation of TBE for a particular modelling langugae comprises two building blocks: The first building block is a graphical editor for defining schemes and transformer definitions, i.e. generic examples of an input scheme and an output scheme. The second building block is an engine (TBE-engine) used for deriving scheme modification operations based on the graphical transformer definition and for performing transformer applications. The main contribution of this thesis is a prototype implementation of the TBE-engine. Since the concept of TBE can be applied in arbitrary modelling languages, a framework (TBE-framework) is provided that enables the convenient implementation of TBE-engines for concrete modelling languages. We demonstrate the implementation of a TBE-engine for modelling language WebML. The TBE-framework is designed to cooperate with different graphical editors. We demonstrate the cooperation of the TBE-engine for modelling language WebML with WebRatio, which is a commercial CASE-tool supporting modelling language WebML. WebRatio does not support TBE-specific constructs directly. Therefore, a further contribution of this thesis is to show how these specific TBE constructs can be specified