Charaf, Hassan

Lengyel, László

Levendovszky, Tihamér

Lengyel László

Levendovszky Tihamér

Charaf Hassan

University of Szeged

Metamodel-Based Modeling and Model Transformation FrameworkSupporting Inheritance and ConstrantsLászló Lengyel, Tihamér Levendovszky and Hassan CharafBecause of the appearance of high level languages, object-oriented technologies and widespreading of CASE tools metamodeling becomes more and more important. Metamodelingis one of the most central techniques both in design of visual languages, and reuse existingdomains by extending the metamodel level. Visual modeling has become indispensable partof software engineering, with aim to raise efficiency in design period of software engineering.Visual modeling helps to realize systems at a higher abstraction level. It is important to providesolutions, which supports storing models building on each other, and which can handle modelsuniformly through optional number of layers.Our implementation called AGSI (Attributed Graph Architecture Supporting Inheritance)is a multipurpose modeling and transformation system, which is able to store models, checkthem against their metamodel, traverse and transform them using graph rewriting (transfor-mation) rules with tree-based notation, export and import them. In AGSI every model has itsmetamodel and every model can be the metamodel of its instances. The most important prin-ciple in AGSI is the following: traversing and modifying the layers must be transparent; everylayer must be handled with the same functions without behaving in a layer-dependent way.In addition to these achievements in metamodel-based graph transformation, this presentationintroduces how we extend this concept to support constraint handling and constraint propa-gation using Object Constraint Language (OCL).In graph rewriting we have rewriting rules consisting of the left hand side graph (LHS) andright hand side graph (RHS). Applying a graph rewriting rule means finding an isomorphic oc-currence (match) of the LHS in the graph the rule being applied to (host graph), and replacingthis subgraph with RHS. Replacing means removing elements which are in the LHS but not inRHS, and adding elements which are in RHS but not in LHS. AGSI goes further: we have LHSbuilt from metamodel elements, so an instantiation of LHS must be found in the host graphinstead of an isomorphic subgraph. Causality is a relation between LHS and RHS elements, itmakes possible to connect an LHS element to an RHS element and to assign an operation tothis connection. Causality and its operation describe what must be accomplished during theapplication of a rewriting rule. It is possible to provide an ordering of the rewriting rules, inother words we control the transformation process by sequencing the rewriting rules. Search-ing is one of the key algorithms, AGSI always tries to use metamodel-based searching involv-ing node type examination, to accelerate the rewriting algorithm. If it is not possible, becauserewriting rule does not contain type information then the algorithm combines depth-first andbreath-first searching strategies. Metamodel-based searching means, that we start searching inmetamodel, firstly we identify the searched nodes by their type. And then we can immediatelyobtain an occurrence of the searched nodes in the model by model-metamodel relation. Thisimmediate node identifying - which means only one database select - significantly acceleratesthe searching algorithm.This presentation discusses the properties of the constraints and the implementation of theirspecial key classes in detail. These constraints specified on meta-layer restrict the modelingpossibilities on instance layer. OCL is a formal language used to express constraints. OCLconsiders the topology and requires the examination of the constraint propagation as well. It ispossible to use OCL for different purposes: (i) to specify invariants on classes and types in theclass model, (ii) to describe pre- and post conditions on operations, (iii) to describe guards (iv)and as a navigation language. It is shown how constraints can be used for rewriting rules andhow they affect the transformation properties.An illustrative case study based on constraint specification in rewriting rules is also pro-vided.80

Metamodel-based modeling and model transformation framework supporting inheritance and constrants : [abstract]

http://acta.bibl.u-szeged.hu/59781/1/cscs_2004_080.pdf

Metamodel-based modeling and model transformation framework supporting inheritance and constrants

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