The ConceptBase system is an implementation of the O-Telos data model.
O-Telos is derived from the knowledge representation language Telos as
designed by Mylopoulos and others
.
While Telos was geared more to its roots in artificial intelligence, O-Telos
is more geared to database theory, in particular to deductive databases.
Nevertheless, O-Telos is to a large degree compatible to the original
Telos specification. In some respects, it generalizes Telos, for example by
removing built concepts for tokens, classes, and meta classes into the language.
In O-Telos, we have essentially just five predefined objects (see appendix
on the axioms of O-Telos).
Telos (and O-Telos) as well also have strong links to the semantic web, in particular to the triple predicates used for defining RDF(S) statements. The main difference is that O-Telos is based on quadruples where the additional components identifies the statement. While RDF(S) has to use special link types to reify triple statements, i.e. to make statements about statements, O-Telos statements are simply referred to by their identifier.
Telos' structurally object-oriented framework generalizes earlier data models and knowledge representation formalisms, such as entity-relationship diagrams or semantic networks, and integrates them with predicative assertions, temporal information, and in particular meta modeling. This combination of features seems to be particularly useful in software information applications such as requirements modeling and software process control. A formal description of O-Telos can be found in [MBJK90, Jeus92]. The following example is used throughout this section to illustrate the language:
company has employees, some of them being managers. Employees have a name and a salary which may change from time to time. They are assigned to departments which are headed by managers. The boss of an employee can be derived from his department and the manager of that department. No employee is allowed to earn more money than his boss.
This section is organized as follows: first, the frame and network representation of the O-Telos language is explained. Then, the predicative sublanguage for deductive rules and integrity constraints are presented. Subsection 2.3 presents a declarative query language which introduces queries as classes with optional predicative membership specification.