VOQL(ID:7540/)

for Visual Object Query Language
References:
  • Kim, Jeonghee; Han, Taisook; Whang, Kyu-Young "Visualization of Path Expressions in a Visual Object-Oriented Database Query Language" Department of Computer Science Korea Advanced Institute of Science and Technology view details Abstract: Although path expressions in object-oriented query languages have materialized the capability of concisely manipulating the nested structures, their presence in query expres- sions require complex semantic considerations. However, none of currently existing visual query languages models such complex query expressions in a concise and intuitive way partly due to either the lack of well-defined syntax and semantics of languages or improper representation of visual constructs for path expressions. In this paper, we present visual modeling of path expressions in a visual object-oriented database query language called Visual Object Query Language (VOQL) and proper modeling of the key features related to multi-valued path expressions. VOQL directly specifies the semantics of multi-valued path expressions by employing the visual notation capable of representing a set inclusion in addition to functional relationships. Specifically, the basic visual constructs called blobs, nested blobs, binding edges, and  flattening edges are introduced. Blobs and nested blobs are used to denote sets of objects that path expressions represent. Binding edges and  flattening edges are designed to visually simulate the notion of variable binding and the notion of dot functions in path expressions. The grammar of these constructs defines the syntactic components such as VOQL terms, VOQL formulas, and VOQL query expressions in a way as in tuple relational calculus. Their semantics are provided by syntax directed translation to corresponding counterparts in Object-Oriented Predicate Calculus (OOPC). Also, in combination with a visual scoping box for universal quantification, the constructs allow explicit visual scoping and expressing the queries with nested quantification and recursion without semantic ambiguities. An explicit specification of the semantics of multi-valued path expressions in a concise and unified visual notation is new and significantly clarifies the semantics of quantified queries in the nested structures in the framework of conventional query and visual notations.
    		•