Database management systems will continue to manage large data volumes. Thus, efficient algorithms for accessing and manipulating large sets and sequences will be required to provide acceptable performance. The advent of object-oriented and extensible database systems will not solve this problem. On the contrary, modern data models exacerbate it: In order to manipulate large sets of complex objects as efficiently as today’s database systems manipulate simple records, query processing algorithms and software will become more complex, and a solid understanding of algorithm and architectural issues is essential for the designer of database management software. This survey provides a foundation for the design and implementation of query execution facilities in new database management systems. It describes a wide array of practical query evaluation techniques for both relational and post-relational database systems, including iterative execution of complex query evaluation plans, the duality of sort- and hash-based set matching algorithms, types of parallel query execution and their implementation, and special operators for emerging database application domains.

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.

: One of the powerful applications of Boolean expression is to allow users to extract relevant information from a database. Unfortunately, previous research has shown that users have difficulty specifying Boolean queries. In an attempt to overcome this limitation, a graphical Filter/Flow representation of Boolean queries was designed to provide users with an interface that visually conveys the meaning of the Boolean operators (AND, OR and NOT). This was accomplished by implementing a graphical interface prototype that uses the metaphor of water flowing through filters. Twenty subjects with no experience with Boolean logic participated in an experiment comparing the Boolean operations represented in the Filter/Flow interface with a textonly SQL interface. The subjects independently performed five comprehension tasks and five composition tasks in each of the interfaces. A significant difference (p < 0.05) in the total number of correct queries in each of the comprehension and compositio...

We describe an approach for multiparadigmatic visual access to databases, which is proposed to achieve seamless integration of different interaction paradigms. The user is provided with an adaptive interface augmented by a user model, supporting different visual representations of both data and queries. The visual representations are characterized on the basis of the chosen visual formalisms, namely forms, diagrams, and icons. To access different databases, a unified data model, the Graph Model, is used as a common underlying formalism to which databases, expressed in the most popular data models, can be mapped. Graph Model databases are queried through the adaptive interface. The semantics of the query operations is formally defined in terms of graphical primitives. Such a formal approach permits us to define the concept of "atomic query", which is the minimal portion of a query that can be transferred from one interaction paradigm to another and processed by the system. Since certain...

The need of a friendly man-machine interaction is becoming crucial for a large variety of applications, in particular, those requiring frequent extraction of information from the database. Experience suggests that traditional query languages are not friendly enough for the casual user: she/he is requested to formulate queries in a textual language, without any iconic or spatial clues to help the querying process. A new generation of languages (visual languages) has been recently investigated, that attempts to make extensive use of the person's instincts and senses. In this paper we propose a fully visual system, called Query by Diagram* (QBD*), which is based on a conceptual data model, a query language defined on this model and a graphical user interface. The main characteristics of the interface are the ease of use, and the availability of a rich set of primitives for both schema selection and query formulation. Unlike many present proposals of graphical query systems, graphical oper...

We propose a framework for database querying providing the user with several interaction paradigms based on different (i.e., form-based, diagrammatic, iconic, and hybrid) visual representations of the database. A unified model, namely the Graph Model, is used as the common underlying model, in terms of which databases expressed in the most common data models can be easily converted. Graph Model databases can be queried by means of the multiparadigmatic interface. The semantics of the query operations is formally defined in terms of the Graphical Primitives. Such a formal approach enables the query manager to maintain the same query consistently in any representation. In the proposed multiparadigmatic environment, the user can switch from one interaction paradigm to another during query formulation, so that the most suitable query representation can be found.

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This paper is about database researchers building interactive information systems. It tells the reader of their initial enthusiasm and user-induced frustration, the consequent discovery of both human-computer interaction (hci) world and the concept of system "usability", and finally their quite successful coupling of hci and databases. Key words: User Interface, Information System, Usability 1. INTRODUCTION It is now generally accepted that factors which mainly influence the success of computerized projects are human and organizational, rather than technological. The mere fact of using computer technologies, even if they are reliable, powerful and innovative, cannot solve work organization problems if the acquired instruments are not in harmony with the attitudes, motivations and competencies of workers in that organization, and also with the social and environmental context of their activities.

In this paper a comparison is presented between the expressive power of generic graphical mechanisms and the various classes of queries (first-order, fixpoint, programming). A precise evaluation of the expressive power of the languages based on such mechanisms (i.e.purely graphical query languages) is shown. Moreover, an informal analysis is provided relatively to the more general class of the visual query languages, supporting also iconic interaction. 1. INTRODUCTION An important design issue in databases is to find an efficient and intuitively appealing query language which allows for expressing all the computable queries (see [23]). It is a well known fact that the graphics represents a friendly mechanism for the humancomputer interaction. In these years, many graphical query languages have been proposed, based on intensional (E-R diagram: GUIDE [34], GORDAS [20, 19], QBD * [7, 4], Pasta-3 [24], etc.) or extensional (instances graphs: G + [15, 16, 17], etc.) data models. Recently so...

The importance of designing query systems which are effective and easy to use has been widely recognized in the database area. Also, it is well known that the adequacy of a system should be tested against actual users in a well monitored experiment. However, very few such experiments have been conducted. The objective of our study is to measure and understand the comparative ease with which subjects can construct queries in two kinds of visual languages, one diagrammatic and the other iconic. More specifically, we are interested in determining if there is significant interaction between: 1) the query class and the query language type; and 2) the type of query language and the experience of the user. Experimental results indicate that the effectiveness of a diagrammatic or an iconic query language varies depending on the classes of queries and the kinds of users. This supports the opinion that an interface offering to the user various visual representations and query modalities is the m...