In this article, we define a semantic data model, where objects' structures are richer than those of their classes. This model is intended to be used in applications such as content-based information retrieval, whose particularity is the fact that objects do not have a predefined conceptual structure that can be fully abstracted in a class schema.
For this purpose, we relax the classical instantiation link between classes and objects, and rebaptize it the
realization
link.
Some of the problems that arise because of this relaxation are investigated, especially when it comes to querying the database. We present a query language for the model that respects the realization link.
The implementation of the model uses a class-based object-oriented model as a meta-model. All of our model concepts are classes in the meta-model, that will be instanciated, for each application of the model, into objects representing all the application features (classes, objects, attributes, queries, ...).
Key words Semantic Model - Information Retrieval - Relaxed Instantiation - Realization Link - Query Language - Meta-Model