Grupo Alarcos · Book chapter · 2006
An Ontological Approach to SQL: 2003
Coral Calero Muñoz, Mario Piattini Velthuis
Databases nowadays are a crucial component of most information systems, playing a strategic role in the support of organizational decisions. Among the different query languages present in the earliest database management systems (DBMSs), SQL has imposed itself as both a de jure and de facto standard. It has been the focus of an intense process of standardization over the years [4-10], where the most important stakeholders, such as DBMS manufacturers, have been actively involved. SQL support can be found today in the vast majority of DBMSs, sometimes with some slight variations. Although the merit of standards is unquestionable, sometimes their relevance may fade away an audience beyond their creators, due either to the lack of understandability, or to the presence of inconsistencies. This last aspect is especially crucial regarding voluminous standards of thousands of pages, for example, the SQL:2003 standard. In a standard like the SQL:2003, there are a considerable number of interweaved concepts, where the semantics of the interrelationships are often very rich. When this happens, an ontology is the best option to complement the standard. An ontology representation language should have rich and formal abstractions for specifying the meaning of terms. UML class diagrams, enriched with OCL (Object Constraint Language) [13], fulfill this purpose. So, an ontology for complementing a standard should represent its relevant concepts and its interrelationships. In this chapter, we will present the ontology we have defined for the last version of the SQL standard, the SQL:2003.The next section will show the historical evolution of the standard, and Sect. 7.3 will present the ontology. After that, we will present an example of ontology instantiation through an object-relational schema defined by means of the standard. Conclusions will appear in the last section.