Visual query systems (VQSs) are query systems for databases that use visual representations to depict the domain of interest and express related requests. VQSs can be seen as an evolution of query languages adopted into database management systems; they are designed to improve the effectiveness of the human-computer communication. Thus, their most important features are those that determine the nature of the human-computer dialogue. In order to survey and compare existing VQSs used for querying traditional databases, we first introduce a classification based on such features, namely the adopted visual representations and the interaction strategies. We then identify several user types and match the VQS classes against them, in order to understand which kind of system may be suitable for each kind of user. We also report usability experiments which support our claims. Finally, some of the most important open problems in the VQS area are described. 1.

The role of the users and their needs are now recognized in the database community. Many efforts are devoted to improve the quality of the interaction between the user and the database. For designing better interfaces that make the systems more usable, the use of suitable metaphors is crucial. The problem we address in this paper is whether an appropriate notion of metaphor can be tailored to the database interaction, so reflecting the peculiarities and needs of this specific field. Our argument originates from a recently published paper that presents a formalism whose aim is to provide a framework for flexible use, definition, and evaluation of visual metaphors in the specific case of database schemata. By discussing such a paper, we try to clarify concepts such as metaphor, data model, visual representation, etc. We also highlight some peculiarities of the database interaction. The considerations presented in this paper should constitute a basis towards a formal approach to metaphorical design for database interaction.

A new query formulation system based on a semantic graph model is presented. The graph provides a semantic model for the data in the database with userdefined relationships. The query formulator allows users to specify their requests and constraints in highlevel concepts. The query candidates are formulated based on the user input by a graph search algorithm and ranked according to a probabilistic information measure. English-like query descriptions can also be provided for users to resolve ambiguity when multiple queries are formulated from a user input. For complex queries, we introduce an incremental approach, which assists users to achieve a complex query goal by formulating a series of simple queries. A prototype system with a multimodal interface using the high-level query formulation techniques has been implemented on top of a cooperative database system (CoBase) at UCLA. 1 Introduction Many database applications require users to formulate ad-hoc queries instead of invocation ...

This paper mainly concentrates on the system prototype, in particular on its user-oriented features, also describing some preliminary usability trials. The paper is organized as follows. Section 2 introduces the system architecture. In Section 3 the formal basis of the multiparadigmatic approach are recalled. In Section 4 the visual representations and interaction mechanisms for the query phase are illustrated, also showing an example of interaction. Section 5 deals with the various visual mechanisms for the query result presentation. Section 6 is devoted to user-related topics, i.e. a description of the user model system component and a brief report on the usability trials. Finally, conclusions are drawn in Section 7.

Undo is seen as essential element of interactive systems. However, despite its prevalence users are often confused by its behaviour and developers often apply undo inconsistently within their systems. This report focuses on singleuser linear undo/redo systems It presents an abstract formal framework for modelling undo and related system extensions, a classification and taxonomy of undo and redo, and formal specifications of each class of undo/redo. This combination of formal and informal analyses clarifies the different kinds of undo/redo that are to be found in interactive systems and helps shed light on the fundamental reflexive nature of undo.