Database Query Language Research Articles

No IFs, ANDs, or ORs: A study of database querying

The difficulty of expressing database queries was examined as a function of the language used. Two distinctly different query methods were investigated. One used a standard database query language, SQL, requiring users to express an English query using a formal syntax and appropriate combinations of boolean operators. The second used a newly designed Truth-table Exemplar-Based Interface (TEBI), which only required subjects to be able to choose examplars from a system-generated table representing a sample database. Through users' choices of critical exemplars, the system could distinguish between interpretations of an otherwise ambiguous English query. Performance was measured by number correct, time to complete queries, and confidence in query correctness. Individual difference analyses were done to examine the relationship between subjects' characteristics and ability to express database queries. Subjects' performance was observed to be both better, and more resistant to variability in age and levels of cognitive skills, when using TEBI than when using SQL to specify queries. Possible reasons for these differences are discussed.

A fuzzy database-query language

Selection conditions for conventional database-query languages are not natural enough to express criteria with fuzzy concepts. To choose some alternatives from a database requires the techniques of multicriteria decision making or conflict resolution. However, some traditional techniques in this area still have some drawbacks, such as inefficiency and independency of criteria. In this paper a fuzzy database-query language is presented and its position in the area of multicriteria decisions making in database applications is discussed and identified. The selection constraints of this query language can accept both crispy and fuzzy conditions.

Human Factors Studies of Database Query Languages

Over the years, SQL has been used repeatedly in human factors experiments measuring the ease of use of database query languages. These experiments have studied a wide range of issues from basic language comparisons, through design issues, to attempts to understand the human cognitive processes involved in querying a database. This paper summarizes the issues and the experiments that have involved SQL.

Extensions to query languages for graph traversal problems

Extensions to database query languages for retrievals that involve inferencing on the nodes and edges of a graph are surveyed. Common types of inferencing are to find paths between two nodes, compute a value for a path such as a distance or an elapsed time, and to choose among alternative paths. The survey is based on the data model (relational or functional), method of extension (iteration, recursion, or special operators), interface style (string or tabular), and restrictions (data- and problem-oriented). The Quel, objected-oriented functional data, G-Whin, and Alpha languages are examined in detail with different values for these properties. The characteristics of other languages are summarized in several tables. The results of the survey indicate the diversity of language extensions and the need to provide data-model and query-language features to address such problems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Query processing techniques in the summary-table-by-example database query language

Summary-Table-by-Example (STBE) is a graphical language suitable for statistical database applications. STBE queries have a hierarchical subquery structure and manipulate summary tables and relations with set-valued attributes. The hierarchical arrangement of STBE queries naturally implies a tuple-by-tuple subquery evaluation strategy (similar to the nested loops join implementation technique) which may not be the best query processing strategy. In this paper we discuss the query processing techniques used in STBE. We first convert an STBE query into an “extended” relational algebra (ERA) expression. Two transformations are introduced to remove the hierarchical arrangement of subqueries so that query optimization is possible. To solve the “empty partition” problem of aggregate function evaluation, directional join (one-sided outer-join) is utilized. We give the algebraic properties of the ERA operators to obtain an “improved” ERA expression. Finally we briefly discuss the generation of alternative implementations of a given ERA expression. STBE is implemented in a prototype statistical database management system. We discuss the STBE-related features of the implemented system.

A mathematical programming generator

This paper describes a mathematical programming generator that interprets problem statements written in the algebraic notation found in journal articles and text-books and outputs statements in the MPS format used by IBM's MPSX mathematical programming system. The system has been implemented in the APL programming language. Although originally designed for stand-alone use, it is currently being used as a component in an expert system that will help users formulate large linear programming models. The paper describes the syntax of the problem definition language and gives some illustrative examples. There are several unique features. First, the user can define objective function, constraint and right-hand-side coefficients as APL expressions. This leads to concise problem statements and also reduces data storage and processing requirements. Second, the system supports an integrated data base query language. Finally, there are a number of aids for model maintenance and sensitivity analysis. The last section of the paper describes the use of MPGEN in the expert system context.

Classification and documentation of vulvar changes: organization of a data bank by personal computer

We developed a simple menu driven database on a personal computer for classification and documentation of vulvar lesions (IBM-PC, dBaseII). Vulvar lesions were classified according to morphological appearance: red, white, dark, ulcer, small tumor (less than 1 cm), large tumor. The data for each category were entered in multiple choice form or as free text and stored in a separate database file. Overlap between categories was observed in vulvar intraepithelial neoplasia, invasive carcinoma and between large and small tumors. For each category an automated table of the frequencies of the different diagnoses is provided, individual patients and variables can easily be accessed through the database query language. We used the database system in the gynecological outpatient clinic of our department during 6 months and were able to document 117 patients with vulvar lesions. In our experience, the database system permits complete documentation according to clinical criteria of all vulvar lesions seen in gynecological practice.

Item selection from menus: the influence of menu organization, query interpretation, and programming experience on selection strategies

Computer generated menus are increasingly being used to simplify the dialog between the human user and the computer system. They are most often provided to help reduce the complexity of the user interface and are characterized by presenting lists of terms (or commands) for easy recognition rather then requiring the recall of these terms from memory. Currently, menu systems are being designed for simplifying the interface to database query languages used to retrieve information stored in computers' databases (Mezzanotte &amp;amp; Kibler, 1984; Williams, 1984; Ogden, Korenshtein, &amp;amp; Smelcer, 1986). A menu-prompted interface supporting a query language would benefit users of database systems by eliminating their need to recall specific database information and by guiding them through the process of query generation.

Simple and clinically useful documentation on the vulva using a personal computer

We developed a simple menu driven database on personal computer for classification and documentation of vulvar lesions (IBM-PC, dBaseII). Vulvar lesions were classified according to morphologic appearance: red, white, dark, ulcer, small tumor (less than 1 cm), large tumor. The data for each category are entered in multiple choice form and stored in a separate database file. For each category an automated table of the frequencies of the different diagnoses is provided, individual patients and variables can easily be accessed through the database query language.

Object identity as a query language primitive

We demonstrate the power of object identities (oid's) as a database query language primitive. We develop an object-based data model, whose structural part generalizes most of the known complex-object data models: cyclicity is allowed in both its schemas and instances. Our main contribution is the operational part of the data model, the query language IQL, which uses oid's for three critical purposes: (1) to represent data-structures with sharing and cycles, (2) to manipulate sets and (3) to express any computable database query. IQL can be statically type checked, can be evaluated bottom-up and naturally generalizes most popular rule-based database languages. The model can also be extended to incorporate type inheritance, without changes to IQL. Finally, we investigate an analogous value-based data model, whose structural part is founded on regular infinite trees and whose operational part is IQL.

Extensible query processing in starburst

Today's DBMSs are unable to support the increasing demands of the various applications that would like to use a DBMS. Each kind of application poses new requirements for the DBMS. The Starburst project at IBM's Almaden Research Center aims to extend relational DBMS technology to bridge this gap between applications and the DBMS. While providing a full function relational system to enable sharing across applications, Starburst will also allow (sophisticated) programmers to add many kinds of extensions to the base system's capabilities, including language extensions (e.g., new datatypes and operations), data management extensions (e.g., new access and storage methods) and internal processing extensions (e.g., new join methods and new query transformations). To support these features, the database query language processor must be very powerful and highly extensible. Starburst's language processor features a powerful query language, rule-based optimization and query rewrite, and an execution system based on an extended relational algebra. In this paper, we describe the design of Starburst's query language processor and discuss the ways in which the language processor can be extended to achieve Starburst's goals.

The computational completeness of extended database query languages

The computational completeness is demonstrated of certain extended database query languages, namely, POSTGRES and GENESIS, and a language defined by A. Aho and J. Ullman (1979). The method used is to implement a Turing machine interpreter in each of the languages. These query languages were defined as extensions to traditional database languages in order to encompass certain specific new applications. Results show that these extensions have already encompassed all the computational power of any programming language. >

Time-by-example query language for historical databases

The authors propose a graphical query language, Time-by-Example (TBE), which has suitable constructs for interacting with historical relational databases in a natural way. TBE is user-friendly. It follows the graphical, two-dimensional approach of such previous languages as Query-by-Example (QBE), Aggregation-by-Example (ABE), and Summary-Table-by-Example (STBE). TBE also uses the hierarchical window (subquery) concept of ABE and STBE. TBE manipulates triple-valued (set-triple-valued) attributes and historical relations. Set-theoretic expressions are followed to deal with time intervals. The BNF specification for TBE is given. >

What you always wanted to know about Datalog (and never dared to ask)

Datalog, a database query language based on the logic programming paradigm, is described. The syntax and semantics of Datalog and its use for querying a relational database are presented. Optimization methods for achieving efficient evaluations of Datalog queries are classified, and the most relevant methods are presented. Various improvements of Datalog currently under study are discussed, and what is still needed in order to extend Datalog's applicability to the solution of real-life problems is indicated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pragmatics and semantics of NQL, a descriptive query language for network databases

In this paper we describe a new query language for databases of network type. The language may be classified as descriptive because queries are formulated with the help of powerful predicates at the level of logical data structures. Predicates are adopted to basic forms of link-based and value-based relationships between objects in a network database. They can be nested and combined in such a way that even complex queries can be posed without explicitly using object variables. Semantics of the language is defined by algorithms which transform queries into set-theoretical expressions. The generated expressions can be interpreted over suitable states of databases.

Moving selections into linear least fixpoint queries

Efficient least-fixpoint query evaluation is crucial to using logic as the query language for relational databases. The authors present a selection transposition algorithm that allows selections that are conjunctions of the predicates of the form column theta value to be evaluated ahead of the least-fixpoint operator while processing linear recursive queries. It is also shown that the algorithm transposes the strongest possible selection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Attribute grammars for the heuristic translation of query languages

This work is motivated by the necessity of providing a high-level user-interface for database query languages to improve the accessibility of information to the nonexpert users. The goal is to achieve portable, adaptable query languages which are supported by mechanisms that allow one to change the query language without changing the implementation. An attribute grammar is used for semantic description of the language. Imprecise terms which are hedges (e.g. very, almost) or nonstandard quantifiers (e.g. many, most, few) are permitted. The structure of the database is transparent to the language because a rule-based approach is taken to determine which relations a query implicitly references. The attributes in the database are treated as linguistic variables for which there exists an abstract description in the metadatabase. These heuristic measures encompass a large class of high-level query languages.

A prototype for the integration of information resource dictionary system and PCTE

The standard for the architecture of an Information Resource Dictionary System (IRDS), proposed by the ANSI X3H2 and the ISO/IEC/JTCI/SC21/WG3 is in process of being developed. After a first phase of common work the two proposals have developed towards different directions. In this article a project, currently under development, is presented, which implements an IRDS prototype as an example of centralized management of information required for both/either software development documentation and software design. In order to allow for the interchange and/or sharing of information between different standard software, a prototype was implemented based on OMS (Object Management System), the PCTE's (Portable Common Tool Environment) database management system which has been defined as a goal of the EEC's ESPRIT project. A parallel prototype based on SQL, the standard database query language for relational data model, was realized to better evaluate the OMS implementation by comparison. On the ground of this experience some preliminary considerations on the different IRDS standard proposals and implementation types are drawn.

A homogeneous relational model and query languages for temporal databases

In a temporal database, time values are associated with data item to indicate their periods of validity. We propose a model for temporal databases within the framework of the classical database theory. Our model is realized as a temporal parameterization of static relations. We do not impose any restrictions upon the schemes of temporal relations. The classical concepts of normal forms and dependencies are easily extended to our model, allowing a suitable design for a database scheme. We present a relational algebra and a tuple calculus for our model and prove their equivalence. Our data model is homogeneous in the sense that the periods of validity of all the attributes in a given tuple of a temporal relation are identical. We discuss how to relax the homogeneity requirement to extend the application domain of our approach.

Extended algebra and calculus for nested relational databases

Relaxing the assumption that relations are always in First-Normal-Form (1NF) necessitates a reexamination of the fundamentals of relational database theory. In this paper we take a first step towards unifying the various theories of ¬1NF databases. We start by determining an appropriate model to couch our formalisms in. We then define an extended relational calculus as the theoretical basis for our ¬1NF database query language. We define a minimal extended relational algebra and prove its equivalence to the ¬1NF relational calculus. We define a class of ¬1NF relations with certain “good” properties and extend our algebra operators to work within this domain. We prove certain desirable equivalences that hold only if we restrict our language to this domain.