Guagliardo, P. (2009). Theoretical foundations of an ontology-based visual tool for query formulation support [Master Thesis, Technische Universität Wien]. reposiTUm. http://hdl.handle.net/20.500.12708/186561
Recent research showed that adopting formal ontologies as a means for accessing heterogeneous data sources has many benefits, in that not only does it provide a uniform and flexible approach to integrating and describing such sources, but it can also support the final user in querying them, thus improving the usability of the integrated system.<br />The Query Tool is an experimental software supporting the user in the task of formulating a precise query -- which best captures their information needs -- even in the case of complete ignorance of the vocabulary of the underlying information system holding the data. The intelligent interface of the Query Tool is driven by means of appropriate automated reasoning techniques over an ontology describing the domain of the data in the information system.<br />Although an implementation does exist, there is no characterisation of the Query Tool from the formal point of view, that precisely describes how such a system works and on which theoretical foundations it relies. Indeed, the central purpose of this thesis is that of providing a formal framework in which the Query Tool's components and operations are defined in a precise and unambiguous way.<br />We will describe what a query is and how it is internally represented by the Query Tool, which operations are available to the user in order to modify the query and how the tool provides contextual feedback about it presenting only relevant pieces of information. Moreover, we will also investigate in detail how a query can be represented in a suitable "linear form", so that it can more easily be expressed in natural language.<br />As a conclusive part of our work, a new implementation of the Query Tool, superseding the existing one and complying with the formal specification, has been devised. At present, the new system includes only the core of the Query Tool and is meant to provide a demonstrative though fully functional implementation based on our framework.