A Survey on Visual Query Systems in the Web Era (extended version) <s> Introduction <s> 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. <s> BIB001 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Introduction <s> During the last decade, multidimensional databases have become common in the business and scientific worlds. Analysis places significant demands on the interfaces to these databases. It must be possible for analysts to easily and incrementally change both the data and their views of it as they cycle between hypothesis and experimentation. In this paper, we address these demands by presenting the Polaris formalism, a visual query language for precisely describing a wide range of table-based graphical presentations of data. This language compiles into both the queries and drawing commands necessary to generate the visualization, enabling us to design systems that closely integrate analysis and visualization. Using the Polaris formalism, we have built an interactive interface for exploring multidimensional databases that analysts can use to rapidly and incrementally build an expressive range of views of their data as they engage in a cycle of visual analysis. <s> BIB002
In recent years, and mainly because of the arrival of the web, more and more collections of data are becoming available to everyone in fields ranging from biology to economy or geography. One of the consequences of this fact is that end users, but not experts in Computer Science, demand easy ways to retrieve data from these collections. Beginning in 1975 with Query By Example (QBE)  there have been many proposals in this direction, that is, to facilitate the work of the final user. In BIB001 , the authors reviewed the so-called Visual Query Systems (VQS) from 1975 to 1996 defined as "systems for querying databases that use a visual representation to depict the domain of interest and express related requests". In this paper, we extend the review from 1997 to date, concentrating our efforts on visual queries to structured information, for example, queries to underlying relational or XML databases. We do not consider the typical search on semistructured documents such as web pages through search engines like Google. Although they are also a good solution for end-users, in this survey we do not take into account natural language interfaces for database query formulation. The main goal of this survey is to answer the following question: to what extent have the VQS been the solution for novel users for querying databases? To answer this question, we have studied two features: web availability of and validatioin undergone by the systems. The first feature indicates that the system was designed to be reached easily by novel users simply by means of a web browser, without the burden of installation and with universal availability. The second feature indicates the widespread use of VQSs in practice. Thus, the more systems commercially available, the greater the extension reached by VQSs. The short answer to the question is that, as far as we know, there is only one system commercially available and designed for the web: Polaris BIB002 . Moreover, we have included two basic features extracted from the paper BIB001 : the visual representation adopted to present the reality of interest and the visual representation adopted to express queries. With respect to web features, we have also considered relevant whether the prototype deals with data formatted for the web, that is, XML data or RDF data. The rest of the paper is organized as follows. In Section 2 we state the method followed for elaborating the survey and we briefly describe the values of the relevant features included in the paper. In Section 3, we have made a systematic review of the selected features for each paper of the survey. Finally, in Section 4, we have drawn several conclusions about the VQSs.