Statistics: (2308 Views) (0 Comments) Print Posted: Thursday, July 05, 2007 Categories: Unified Modeling Language (UML), Data Analysis & Modeling

When it comes to providing reliable, flexible and efficient object persistence for software systems, today's designers and architects are faced with many choices. From the technological perspective, the choice is usually between pure Object-Oriented, Object-Relational hybrids, pure Relational and custom solutions based on open or proprietary file formats (eg. XML, OLE structured storage). From the vendor aspect Oracle, IBM, Microsoft, POET and others offer similar but often-incompatible solutions.

This article is about only one of those choices, that is the layering of an object-oriented class model on top of a purely relational database. This is not to imply this is the only, best or simplest solution, but pragmatically it is one of the most common, and one that has the potential for the most misuse.

We will begin with a quick tour of the two design domains we are trying to bridge: firstly the object-oriented class model as represented in the UML, and secondly the relational database model.

For each domain we look only at the main features that will affect our task. We will then look at the techniques and issues involved in mapping from the class model to the database model, including object persistence, object behaviour, relationships between objects and object identity. We will conclude with a review of the UML Data Profile (as proposed by Rational Software).

Some familiarity with object-oriented design, UML and relational database modelling is assumed.

Author: Geoffrey Sparks