A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> A system to query databases using diagrams as a standard user interface is proposed. The system, called Query by Diagram* (QBD*), makes use of a conceptual data model, a query language on this model, and a graphical user interface. The conceptual model is the entity-relationship model. The query language, whose expressive power allows recursive queries, supports visual interaction. The main characteristics of the interface are ease of use and the availability of a rich set of primitives for schema selection and query formulation. The expressive power of QBD* and G/sup +/, which are the only languages allowing recursive queries to be expressed graphically are compared. > <s> BIB001 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> This paper presents a general purpose object query system and language, called QBI (Query by Icon), that involves the manipulation of icons for composing a query. It requires neither special knowledge of the content of the underlying database or understanding of the details of the database schema, hence it is equally useful to both unsophisticated and expert users. A user perceives the database as classes of objects and generalized attributes while the system internally maintains a schema of the underlying database rich in semantic information. No relationship specification is required for composing a query. Furthermore, automatic natural language feedback and cardinality constraints analysis assist users in query specification. > <s> BIB002 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Formulating non-trivial queries in relational languages such as SQL and QBE can prove daunting to end users. ConQuer is a conceptual query language that allows users to formulate queries naturally in terms of elementary relationships. operators such as and, of', snot' and maybe contextual forclauses and object-correlation, thus avoiding the need to deal explicitly with implementation details such as relational tables, null values. outer joins, group-by clauses and correlated subqueries. While most conceptual query languages are based on the Entity-Relationship approach, ConQuer is based on Object-Role Modeling (ORM), which exposes semantic domains as conceptual object types. allowing queries to be formulated via paths through the information space. As a result of experience with the first implementation of ConQuer, the language has been substantially revised and extended to become ConQuer-II. and a new tool, ActiveQuery, has been developed with an improved interface. ConQuer-II's new features such as arbitrary correlation and subtyping enable it to be used for a wide range of advanced conceptual queries. <s> BIB003 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Resolving different levels of heterogeneity present in heterogeneous database environments is a subject that has been addressed in a number of research projects. Graphical user interfaces are becoming the de-facto form of user interface in many application areas, including database management systems. The use of a popular visualisation notation to present schemas at an abstract level and to permit direct user manipulation of this visualisation in formulating queries is one of the most widespread approaches to providing database graphical user interfaces. The existence of a variety of visualisation notations (which are in common use to visualise schemas) introduces additional heterogeneity to a distributed system, in visual representation at the end-user interface level. This paper describes the use of meta-programming techniques which are applied to resolve this visual model heterogeneity on existing databases, by allowing a user to select a preferred visualisation notation, both to view the schema and to query the database. <s> BIB004 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> The WWW has a great potential of evolving into a globally distributed digital document library. The primary use of such a library is to retrieve information quickly and easily. Because of the size of these libraries, simple keyword searches often result in too many matches. More complex searches involving boolean expressions are difficult to formulate and understand. This paper describes QBT (Query By Templates), a visual method for formulating queries for structured document databases modeled with SGML. Based on Zloof's QBE (Query By Example), this method incorporates the structure of the documents for composing powerful queries. The goal of this technique is to design an interface for querying structured documents without prior knowledge of the internal structure. This paper describes the rationale behind QBT, illustrates the query formulation principles using QBT, and describes results obtained from a usability analysis on a prototype implementation of QBT on the Web using the Java/sup TM/ programming language. <s> BIB005 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> During the past few years our research efforts have been inspired by two different needs. On one hand, the number of non-expert users accessing databases is growing apace. On the other, information systems will no longer be characterized by a single centralized architecture, but rather by several heterogeneous component systems. In order to address such needs we have designed a new query system with both user-oriented and multidatabase features. The system's main components are an adaptive visual interface, providing the user with different and interchangeable interaction modalities, and a “translation layer”, which creates and offers to the user the illusion of a single homogeneous schema out of several heterogeneous components. Both components are founded on a common ground, i.e. a formally defined and semantically rich data model, the Graph Model, and a minimal set of Graphical Primitives, in terms of which general query operations may be visually expressed. The Graph Model has a visual syntax, so that graphical operations can be applied on its components without unnecessary mappings, and an object-based semantics. The aim of this paper is twofold. We first present an overall view of the system architecture and then give a comprehensive description of the lower part of the system itself. In particular, we show how schemata expressed in different data models can be translated in terms of Graph Model, possibly by exploiting reverse engineering techniques. Moreover, we show how mappings can be established between well-known query languages and the Graphical Primitives. Finally, we describe in detail how queries expressed by using the Graphical Primitives can be translated in terms of relational expressions so to be processed by actual DBMSs. <s> BIB006 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Abstract The adoption of a visual interface can simplify the query formulation process in DBMSs by enabling naive users to interact with a friendly environment. In this work, we propose a visual query language based on a diagrammatic paradigm, used for both data and query representation. The external data model is called vision and is made up of the visual primitives of concept and association. The external query model is based on the definition of a viewpoint, which is a perspective for accessing data defined dynamically by selecting a concept of primary interest. Internally, the data model is relational and the query language is SQL. An intermediate graph-based model ensures consistent mapping between the visual and the relational worlds. Our language has been implemented within a tool which can be mounted on top of any relational DBMS supporting ODBC. The system has been tested with naive users; the results of the experiment are reported and compared with those obtained with other visual languages. <s> BIB007 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Hyperlog is a declarative, graph based language that supports database querying and update. It visualizes schema information, data, and query output as sets of nested graphs, which can be stored, browsed, and queried in a uniform way. Thus, the user need only be familiar with a very small set of syntactic constructs. Hyperlog queries consist of a set of graphs that are matched against the database. Database updates are supported by means of programs consisting of a set of rules. The paper discusses the formulation, evaluation, expressiveness, and optimization of Hyperlog queries and programs. We also describe a prototype implementation of the language and we compare and contrast our approach with work in a number of related areas, including visual database languages, graph based data models, database update languages, and production rule systems. <s> BIB008 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> In this paper a visual approach to querying in large spatial databases is presented. A diagrammatic technique utilising a data flow metaphor is used to express different kinds of spatial and non-spatial constraints. Basic filters are designed to represent the various types of queries in such systems. Icons for different types of spatial relations are used to denote the filters. Different granularities of the relations are presented in a hierarchical fashion when selecting the spatial constraints. Spatial joins and composite spatial and non-spatial constraints are represented consistently in the language. <s> BIB009 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Abstract We report on an iconic interface that implements a restricted subset of SQL commands for querying a database. Database queries and the query language's tokens (verbs, adjectives, etc.) are represented by icons. To construct a query, the user composes structured iconic expressions according to the grammar of the iconic language. The language and grammar include rules for iconic construction (Quadral Composite Icons and Serial Composite Icons). In brief, the user visually queries the database by issuing structured iconic queries composed in a systematic manner. The paper describes the syntactic and semantic principles behind structured iconic expressions and the way that these principles have been implemented in an iconic interface. User evaluation is informally reported, and the role of metaphor in the design and interpretation of icons is discussed. <s> BIB010 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Recent database applications are typically oriented towards a large set of non-expert users, and therefore, they need to be equipped with suitable interfaces facilitating the interaction with the system. Moreover, the incorporation of the time dimension in database systems is a desirable feature. Indeed, several temporal data models and the corresponding textual query languages have been proposed. However, there is a limited amount of research concerning the investigation of user-oriented languages for querying temporal databases. Our proposal addresses such a need. In particular, we propose a visual query environment, namely Temporal Visual Query Environment (TVQE) which provides an easier interaction of the user with temporal databases. The system adopts a diagrammatic representation of the database schema (including temporal classes and relationships) and a "graphical notebook" as interaction metaphor. In our approach, non-database experts are released from syntactical difficulties which are typical of textual languages, and they can easily express temporal queries by means of elementary graphical operations (e.g. click on a node label). Differently from many proposals in the field of visual query languages, the language underlying TVQE is provided with formal syntax and semantics. It is based on a minimal set of temporal graphical primitives (TGPs), which are defined on a Temporal Graph Model (TGM), with visual syntax and object-based semantics. In this paper we mainly concentrate on the formal aspects of TVQE, and provide some hints on the visual interaction mechanisms and implementation issues. <s> BIB011 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> This paper introduces SEEQ - a System for Enhanced Exploration and Querying. It is a visual query system for databases that uses a diagrammatic visualization for most user interaction. The database schema is displayed as a graph of the data model including classes, associations and attributes. The user formulates the query in terms of direct manipulation as a graph of the schema objects, additional operators and constants. The output of the query is visualized as a graph of instances and constants or in some other format that is appropriate for the data. SEEQ can operate on arbitrary relational data base provided that the schema is in XML format. <s> BIB012 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> In contrast to a traditional setting where users express queries against the database schema, we assert that the semantics of data can often be understood by viewing the data in the context of the user interface (UI) of the software tool used to enter the data. That is, we believe that users will understand the data in a database by seeing the labels, drop-down menus, tool tips, or other help text that are built into the user interface. Our goal is to allow domain experts with little technical skill to understand and query data. In this paper, we present our GUi As View (Guava) framework and describe how we use forms-based UIs to generate a conceptual model that represents the information in the user interface. We then describe how we generate a query interface from the conceptual model. We characterize the resulting query language using a subset of the relational algebra. Since most application developers want to craft a physical database to meet desired performance needs, we present here a transformation channel that can be configured by instantiating one or more of our transformation operators. The channel, once configured, automatically transforms queries from our query interface into queries that address the underlying physical database and delivers query results that conform to our query interface. In this paper, we define and formalize our database transformation operators. The contributions of this paper are that first, we demonstrate the feasibility of creating a query interface based directly on the user interface and second, we introduce a general purpose database transformation channel that will likely shorten the application development process and increase the quality of the software by automatically generating software artifacts that are often made manually and are prone to errors. <s> BIB013 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Database researchers have striven to improve the capability of a database in terms of both performance and functionality. We assert that the usability of a database is as important as its capability. In this paper, we study why database systems today are so difficult to use. We identify a set of five pain points and propose a research agenda to address these. In particular, we introduce a presentation data model and recommend direct data manipulation with a schema later approach. We also stress the importance of provenance and of consistency across presentation models. <s> BIB014 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Even though XQuery has become a standard for querying semi-structured data, its syntax is too complex for occasional users. This paper describes a user friendly interface called IFOX (Interface For Ordered XQuery) that enables non experienced users to build easily complex XQueries. To that end, we use an algebraic-like representation to build XQueries. This representation is based on the XAlgebra described in [17]. Moreover, many applications require answers to queries to be order sensitive. For example, in a biomedical application where a set of genes is stored in a XML file, the order in the output when querying these data is crucial. With issue in mind, we propose a normalization process which not only preserves order in answers to queries but also enables optimization techniques. <s> BIB015 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <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> BIB016 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Querying databases is a common daily task carried out by a great deal of end-users who do not have specific skills in SQL language. Today, most of the database interaction is achieved by means of query interfaces provided by the database environment. However, most of these interfaces suffer from expressive limitations, since they are mostly based on metaphors that drastically restrict the expressiveness of the SQL language that is generated and executed in the background. In this paper, we present a visual interaction language and tool focused on easily querying databases by end-users. We make no assumption on the level of the user's experience with query languages, as our visual metaphor is intended for querying databases by unskilled end-users and also leveraging the restriction on the expressiveness of the queries created by them. We also report on some late braking results obtained by an experiment carried out with real users. <s> BIB017 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> Given a graph database D and a query graph g, an exact subgraph matching query asks for the set S of graphs in D that contain g as a subgraph. This type of queries find important applications in several domains such as bioinformatics and chemoinformatics, where users are generally not familiar with complex graph query languages. Consequently, user-friendly visual interfaces which support query graph construction can reduce the burden of data retrieval for these users. Existing techniques for subgraph matching queries built on top of such visual framework are designed to optimize the time required in retrieving the result set S from D, assuming that the whole query graph has been constructed. This leads to sub-optimal system response time as the query processing is initiated only after the user has finished drawing the query graph. In this paper, we take the first step towards exploring a novel graph query processing paradigm, where instead of processing a query graph after its construction, it interleaves visual query construction and processing to improve system response time. To realize this, we present an algorithm called G BLENDER that prunes false results and prefetches partial query results by exploiting the latency offered by the visual query formulation. It employs a novel action-aware indexing scheme that exploits users' interaction characteristics with visual interfaces to support efficient retrieval. Extensive experiments on both real and synthetic datasets demonstrate the effectiveness and efficiency of our solution. <s> BIB018 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> In large scale model based development, analysis level models are more like knowledge bases than engineering artifacts. Their effectiveness depends, to a large degree, on the ability of domain experts to retrieve information from them ad-hoc. For large scale models, however, existing query facilities are inadequate. The visual model query language (VMQL) is a novel approach that uses the respective modeling language of the source model as the query language, too. The semantics of VMQL is defined formally based on graphs, so that query execution can be defined as graph matching. VMQL has been applied to several visual modeling languages, implemented, and validated in small case studies, and several controlled experiments. <s> BIB019 </s> A Survey on Visual Query Systems in the Web Era (extended version) <s> Validation <s> XML is the standard way of representing and storing rapidly-growing semi-structured data on the Internet. While XQuery has been proposed by W3C as the standard query language for XML data, the complexity of the language is the major overhead for users to express the queries and for software to process the queries efficiently. Considering mobile devices are more popular than desktop computers, expressing and/or processing XQuery becomes even more cumbersome on mobile devices. This paper proposes a visual XQuery specification language called VXQ. By intuitive abstractions of XML and XQuery, the proposed system can generate XQuery queries for users with little knowledge about XML and the language. The proposed visual language is easier to use and more expressive than previous proposals, and is also suitable for mobile devices where typing is not desired. Furthermore, we extend our proposed visual XQuery to support query rewriting and optimization for multiple XQuery systems. Experiments show that, in practice, our query rewriting reduces the query execution time significantly. <s> BIB020
The validation of an idea can be done from several points of view. Regarding query systems, there are, at least, two dimensions: usability and performance. For example, paper BIB020 focuses on performance and explains query rewriting techniques that improve the query evaluation performance so that the query exection time is reduced. However, in this paper we concentrate on the usability dimension, that is, the experiments made with users in order to determine the ease of use of the proposed prototype. For this feature, the list of values is: -Only prototype -Prototype tested with users -Prototype tested in a real environment -Commercial tool Next, we describe briefly each value of this feature. The option only prototype means that a prototype has been built but no test has been made with users. The value prototype tested with users means that several experiments have been carried out in order to determine the usability of the prototype. The value prototype tested in a real environment means that it has been used for real tasks in a particular setting, for example in a department of a university. Finally, the option commercial tool means that the VQS has been fully implemented, offered to the public and is in real use in diverse installations. In column 5 of Table 2 and of Table 3 , we summarise the validation method of the VQSs. Only prototype There is a prototype of VISUAL  which implements a mapping from VISUAL to OQL. The paper claims that it has been designed with efficiency and ease of use. Paper BIB003 presents a query engine for Conquer-II written in C++. It consists of about 25000 lines of code and 83000 lines shared with InfoModeler. Paper BIB004 has implemented a prototype where the user can select between OMT, EER and a tabular representation for displaying schemas. On top of this, the query prototype is capable of handling select/project/join queries. Paper BIB008 implements an architecture of Hyperlog, which consists of several interconnected modules. The user interacts with the editor for expressing queries. Ifox BIB015 offers a prototype with five areas(see Figure 24 ): input visualization, query visualization, output visualization, operator selection and operator specification. The first area show the XML schema, the second is used for graphically specifying the query. The third shows the result of the query. The last two are about the Xoperators of the queries. Prototype tested with users Paper BIB005 presents QBT and was tested with novice and experienced users. The results show that QBT is significantly more satisfying to the users than traditional form-based approaches. Paper BIB006 offers a multiparadigm interface 'where various equivalent user interfaces can be defined on the basis of the same formalisms, and different databases can be dealt with in a uniform way'. They state that this interface was being tested with real users but they do not offer any result of this testing. The VISIONARY system BIB007 offers a section of comparison experiments with QBD* BIB001 and QBI BIB002 . As a conclusion, VISIONARY is slightly better than QBD* and much better than QBI. Paper BIB009 implements a prototype with the DELPHI system. Evaluation is underway with two categories of users: with experience and without experience in GIS. Iconic SQL BIB010 offers a fully functional and working implementation developed under Linux on a Pentium PC. They performed an evaluation to see how the context influences identification and association. For this purpose, they set people a task and asked them to pick out relevant icons. In some cases, the user did not guess correctly the icons but the more the context develops in a session, the fewer details are needed in an icon for identification purposes. The initial interface of TVQE BIB011 was improved based on the suggestions of users who had participated in a preliminary experiment with the TVQE prototype, giving place to the version described in the paper. The prototype was implemented in Java using JDBC as interface to the DBMS. The development of CQL  adopted a user-centered approach in that it 'involves participants who are representative of the intended class of end-users in the interface development process'. The first step was the elaboration of a mock-up with the purpose of eliciting comments from end-users. These comments led to a second version of the interface. The two interfaces were implemented as prototypes and were compared. The conclusions are that end-users perform better with the second prototype and they take lesss time to formulate queries with the first prototype. Taking these results into account, they prepared the final production interface shown in Figure 30 . In BIB017 , the authors issued a study for obtaining users' satisfaction related to the ease of use of VISQUE, which reflects that the tool is easy to use and that casual users may need some initial help with the tool. The study was done with 12 real users having domain knowledge about database systems but not about SQL. The idea of Gblender BIB018 was tested with three users and was centered on the response time rather than on the usability. With respect to the response time, GBlender outperforms other state-of-the-art graph proposals. The VMQL system BIB019 has been tested with several users in order to establish the degree of usability as compared to OCL and the logical query facility. The results show better results for all tasks done by VMQL than done by OCL. The tasks were reading queries or writing queries. Tested in a real environment Paper BIB013 has been validated by the use of CORI analysts. CORI seeks to improve the practice of endoscopy by conducting studies on patient data. They distribute a software with which the clinician enters data that describes endoscopic procedures. From this data, the analysts elaborate reports for use by physicians. The Guava framework helps in extracting the data from the database. Paper BIB012 proposes the SEEQ system, which is utilized in the student information system of the university of the authors. The tool is implemented in Java, uses the Swing GUI toolkit and the connexion to the database is by means of JDBC. The MiMi system BIB014 proposes up to five interfaces and has tested them with biologists. They draw many interesting conclusions. For example, that "when users are presented with multiple ways to access the information but do not understand the underlying differences between the views, they tend to become confused and lose trust in the system". Moreover, they have identified the problems non-expert users have with the interfaces. Some of the problems are painful relations, painful options or unexpected pain. Commercial tool The POLARIS system of BIB016 has been widely tested because it has been commercialized by Tableau Software as Tableau Desktop and is currently in use by thousands of companies and tens of thousands of users. With all this experience, they have validated the effectiveness of their proposal.