|
|
|
 |
|
 |
|
Visualization of Path Expressions in a Virtual Object-Oriented Database Query Language
|
Jeonghee Kim,
Taisook Han, and
Suk Kyoon Lee
View Paper (PDF)
Return to Session 2B: Visualization and Multimedia Databases
Path expressions have been accepted for concisely manipulating
the nested structures in complex object-oriented query expressions. However,
previous visual query languages hardly represent such query expressions in a
concise and intuitive way partly due to improper visual representation of path
expressions and partly due to lack of well-defined syntax and semantics of
languages. In this paper, we present visual modeling of path expressions in a
visual object-oriented database query language called Visual Object-Oriented
Query Language (VOQL) which has excellent expressive power for sets, simple and
intuitive syntax, and well-defined semantics. This is enabled by
explicitlySpecifying the semantics of multi-valued path expressions based on
the visual notation capable of representing set relationships in addition to
functional relationships. The basic visual constructs called blobs and nested
blobs denote sets of objects that path expressions represent while the
constructs called binding edges and flattening edges visually simulate the
notions of variable binding and dot functions in path expressions respectively.
Based on the constructs, the grammer of VOQL defines the syntactic components
while the semantics of query expressions are provided by syntax-directed
translation to the counterparts in the extended relational calculus. Also, the
visual constructs allow modeling of restricted universal quantification with a
visual scoping box and effectively represent nested quantification and
recursive queries without semantic ambiguities. An explicit specification of
the semantics of multi-valued path expressions in a concise and unified visual
notation is new and visually clarifies the semanticsof quantified queries in
the nested structures.
Copyright(C) 2000 ACM
|
|
|
|
|
|
|
