Complex Model-Defined Constraints for Database Access with the Entity Container

G. Schmoelzer, C. Kreiner, Z. Kovács, E. Teiniker, and R. Weiss (Austria)


Data modeling, database tools, constraint checking.


Data modeling is a well known mechanism describing data structures at a high level of abstraction. Such models are of ten used to automatically create database structures, and to generate code structures used to access databases. This has the disadvantage of losing data constraints that might be specified in data models for data verification. In this paper we follow an approach using the Entity Container (EC), an object–oriented and model–based data cache, for accessing Relational Database Management Systems (RDBMs). The EC provides data access based on entity classes defined in a data model, and transparently supports several persistency mechanisms. A Database Access Layer (DBAL) provides an Object/Relational (O/R) mapping converting data ob jects to the relational model of a RDBMS and vice versa. In order to ensure data consistency and to improve quality of data intensive systems, we discuss the concept of strong model constraint checking at the level of a data cache, the EC. Data modeling, constraint checking, and the atomicity problem as a consequence of constraint checking is elab orated. Analog to databases, a mechanism for grouping multiple actions to a single unit of work is required, here referred as Microtransaction (MT). Properties, combina tion with database transactions, and intended use of such MTs are presented.

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