The GOQL Language and its Formal Specifications

The Graphical Object Query Language (GOQL) is a graphical query language that complies with the ODMG standard and runs on top of the o2 DBMS. The language provides users with the User’s View (UV) and the Folders Window (FW), which serve as the foundation upon which end-users can pose ad-hoc queries. The UV is a graphical representation of any underlying ODMG scheme. Among its advantages is that it hides from end-users most of the perplexing details of the object-oriented database model, such as methods, hierarchies and relationships. To achieve this, the UV does not distinguish between methods, attributes and relationships, it encapsulates is -a hierarchies and it utilises a number of desktop metaphors whose semantics can be easily understood by end-users. The FW is a condensed version of the UV and provides the starting point for constructing queries. In this paper, we demonstrate, using an example, the UV and the FW and the way they support the construction of graphical queries. We then present the formal specifications of the language. We first give a formal definition of an object-oriented database schema in the GOQL model. The UV is then formally defined as a mapping from a GOQL object-oriented database schema. The formal definition of the UV allows us to formally define the graphical constructs of GOQL and the syntax analysis of the language.