Quelo is a formal framework and a tool supporting the user in the task of formulating a precise query – which best captures her information needs – even in the case of complete ignorance of the vocabulary of the underlying information system holding the data. The intelligent interface is driven by means of appropriate automated reasoning techniques over an ontology describing the domain of the data in the information system. The output is a query which may be expressed in Datalog, SPARQL, or SQL. The formal framework defines what a query is and how it is internally represented, which operations are available to the user in order to modify the query and how contextual feedback is provided about it presenting only relevant pieces of information. The elements that constitute the query interface available to the user, providing visual access to the underlying reasoning services and operations for query manipulation, are precisely defined in their function by the framework. The Quelo tool provides suitable a representation of the query interface in “linear form”, which is materialised in natural language.


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. We introduce a framework that enables access to heterogeneous data sources by means of a conceptual schema and supports the users in the task of formulating a precise query over it. In describing a specific domain, the ontology defines a vocabulary which is often richer than the logical schema of the underlying data and usually closer to the user's own vocabulary. The ontology can thus be effectively exploited by the user in order to formulate a query that best captures their information need. The user is constantly guided and assisted in this task by an intuitive visual interface, whose intelligence is dynamically driven by reasoning over the ontology. The inferences drawn on the conceptual schema help the user in choosing what is more appropriate with respect to their information need, restricting the possible choices to only those parts of the ontology which are relevant and meaningful in a given context. The most powerful and innovative feature of our framework lies in the fact that not only do not users need to be aware of the underlying organisation of the data, but they are also not required to have any specific knowledge of the vocabulary used in the ontology. In fact, such knowledge can be gradually acquired by using the tool itself, gaining confidence with both the vocabulary and the ontology. Users may also decide to just explore the ontology without actually querying the information system, with the aim of discovering general information about the modelled domain. Another important aspect is that only queries that are logically consistent with the context and the constraints imposed by the ontology can be formulated, since contradictory or redundant pieces of information are not presented to the user at all. This makes user's choices clearer and simpler, by ruling out irrelevant information that might be distracting and even generate confusion. Furthermore, it also eliminates the often frustrating and time-consuming process of finding the right combination of parts that together constitute a meaningful query. For this reason, the user is free to explore the ontology without the worry of making a wrong choice at some point and can thus concentrate on expressing their information need at best. Queries can be specified through a refinement process consisting in the iteration of few basic operations: the user first specifies an initial request starting with generic terms, then refines or deletes some of the previously added terms or introduces new ones, and iterates the process until the resulting query satisfies their information need. The available operations on the current query include addition, substitution and deletion of pieces of information, and all of them are supported by the reasoning services running over the ontology. Quelo relies on a web-based client-server architecture consisting of three components:

Online Tool