Implementation of the ERM-model repository in CASE-system Oracle Designer

Recently researchers of the automated means for information system development pursue the goal to increase of automation degree, developer labor productivity, and also quality of the result received by means of CASE-systems. For achievement of these purposes it is necessary to improve analysis and design models, tools of intermodel transformation and final generation of executed artifacts. Testing and debugging of the newly proposed means are inconceivable without creation of a research prototype of the future CASE-system. This article is devoted to development of a kernel of such system - a repository. Distinctive feature of this development is orientation to use the semantic data model «Entity - Relationship - Mapping» (ERM-model) for information modeling. Along with the traditional functional requirements demanded for automated development tools, the research prototype of a repository has a number of important nonfunctional requirements: - the system should have the program interface allowing to work with schemes by means of external applications, such as the graphic editor of ERM-schemes, generator of relational schemes and other tools which will be realized in the future; - the system should have the user interface giving dialogue access to objects of a repository; - as the ERM-model actively develops, its metascheme will be frequently changed, hence, the architecture of a prototype should be flexible and give possibility to reuse of earlier developed components. It is possible to distinguish two alternative ways of the ERM-repository realization. The first way consists in creation of own repository «from scratch» based on of permanent data store. Relational DBMS can acts as data store, for example. The second way consists in expansion of any already available CASE-mean. During the analysis of base means CASE-system Oracle Designer (OD) is taken as a platform for creation of the ERM-scheme repository. The central part of this system is the repository containing project specifications at all its stages and providing coordinated work of all its participants, whatever roles they played in the project. For access to the repository and management of it Repository Object Navigator is available as well as specialized dialogue tools. It is a universal instrument, allowing looking through and modifying almost all objects stored in a repository. Before defining the ERM-metascheme in the metascheme of an OD-repository, it has been decided to realize this metascheme in the form of a relational database at first, to check up working capacity of the received structures on real examples of the ERM-schemes and typical transactions of their change. The relations received during test realization have been transformed to sets of element and association types and successfully added in the metascheme of a repository by means of Maintain User Extensions utility of Repository Administration Utility tool. During repository designing the decision to isolate logic of work with structural ERM-model entities in a separate package (ERM_API) was accepted. Its procedures and functions carry out adding, modifying, deleting and retrieving objects of this model. The access mechanism encapsulates calls to a repository through standard OD API. Each call of any procedure or function generates one or more calls of OD API, preliminary preparation for them, and the subsequent processing and return of results. The problem of realization of the ERM-scheme checks on consistency is one of key on repository creation. It is important, that at any moment the analytical and design data, stored in the repository, were complete and consistent. For maintenance of check inevitability at any changes it has been decided to realize a package of the ERM-scheme check functions (ERM_CHECK) as expansion of package OD API, in appropriate way having changed the last. Timely creation of the ERM-repository has allowed developing, testing and debugging of many other subsystems of the research CASE tool for ERM-model which should become the practical proof of an urgency and working capacity of the last. Major of these subsystems are the graphic editor of ERM-schemes realizing a technique of ERM-modeling, and as much as possible effective compiler of ERM-schemes in the relational model, generating besides CREATE TABLE commands of view and trigger creation.

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