CSDL, a language for designing conceptual schemata, is described. The language provides tools to ease the translation of hnowledge about data into a formal conceptual schema.
Contemporary database technology leaves the task of designing the conceptual schema (CS) to the database Administrator (DBA). Unassisted the DBA has to translate manually the unstructured knowledge about the data first into logical and then into physical structures, making all the organizational decisions. In many cases, the DBA will be presented by the potential users with incomplete requirements about the data and its semantics either because these users are inexperienced or have a partial and/or limited understanding of the data. Even putting aside incomplete requirements, the DBA still has difficulties in grasping the totality of the data and the complex interactions within it. Manually translating unstructured knowledge into symbols and algorithms is time consuming and increases the likelihood of making errors because no metnoaology exists.
This paper describes some of the tools provided by CSDL which i's a language for designing conceptual schemata of databases. The purpose of CSDL is to ease the translation of knowledge about the data into a formal CS. CSDL is only the means with which the DBA or designers of the CS can express their thoughts and understanding temporarily or permanently. CSDL also helps to debug the CS through diagnostics and tracing facilities in the same way as most programming languages.
At the design level, the designer is concerned with the behaviour of the entities and the relationships among them, and not by the way they are symbolically represented in the computer. The behaviour and the relationships among the abstract objects are expressed in terms of a set of semantic operations that are meaningful for those objects. This approach is in agreement with the approach taken in programming methodology ~3 .
The set of semantic operators in CSDL includes operators for creating, naming, linking, grouping, organizing objects and defining transactions on objects. The semantic operators are the only direct means for creating and manipulating the abstract objects that model the application. By adhering to a strict programming discipline, syntactic correctness of the created CS can be guaranteed.
CSDL also provides some support facilities which allow the designer to check the created CS. These include displays, type checking, modification operations and consistency checkers. These have been separated from the semantic operators as they are directly related to the media used by CSDL.