Database Query Language Research Articles

Fuzzy database query languages and their relational completeness theorem

Two fuzzy database query languages are proposed. They are used to query fuzzy databases that are enhanced from relational databases in such a way that fuzzy sets are allowed in both attribute values and truth values. A fuzzy calculus query language is constructed based on the relational calculus, and a fuzzy algebra query language is also constructed based on the relational algebra. In addition, a fuzzy relational completeness theorem such that the languages have equivalent expressive power is proved. >

A relational-calculus query language for historical databases

In this paper, an approach to handle time in relational query languages is outlined. The approach is based on extending Boolean and comparison operators by allowing their operands to be sets of intervals. The proposed temporal logic is shown to satisfy the properties of the normal Boolean logic. A relational-calculus query language using the extended logic is developed. The extended logic presented in this paper provides a good degree of flexibility in expressing different temporal requirements and therefore promises to be a successful approach for designing powerful temporal query languages.

CIM for Small Companies

A “low cost” modular CIM concept especially for small and medium sized companies has been developed and installed in an Austrian company, which is producing welding transformers. This modular CIM solution is established in order to embed all its components into the existing infrastructure of the company, according to their demands. This concept is based on the hardware of a local area network of PCs (operating system MS-DOS) and a database computer (operating system UNIX). The realization of this solution is accomplished by using the C-programming language, Informix database and Informix-Sql as database query language, in order to create the custom applications with database management. With these tools, the structure of a relational database and the ANSI-standard Structured Query Language are provided. This concept is being described and an application example is discussed with special emphasis on problems of information.

DOODLE: a visual language for object-oriented databases

In this paper we introduce DOODLE, a new visual and declarative language for object-oriented databases. The main principle behind the language is that it is possible to display and query the database with arbitrary pictures . We allow the user to tailor the display of the data to suit the application at hand or her preferences. We want the user-defined visualizations to be stored in the database, and the language to express all kinds of visual manipulations. For extendibility reasons, the language is object-oriented. The semantics of the language is given by a well-known deductive query language for object-oriented databases. We hope that the formal basis of our language will contribute to the theoretical study of database visualizations and visual query languages, a subject that we believe is of great interest, but largely left unexplored.

Two-dimensional specification of universal quantification in a graphical database query language

A technique is proposed for specifying universal quantification and existential quantification (combined with negation) in a two-dimensional (graphical) database query language. Unlike other approaches that provide set operators to simulate universal quantification, this technique allows a direct representation of universal quantification. Syntactic constructs for specifying universal and existential quantifications, two-dimensional translation of universal quantification to existential quantification (with negation), and translation of existentially quantified two-dimensional queries to relational queries are presented. The resulting relational queries can be processed directly by many existing database systems. The authors claim that this technique renders universal quantifications easy to understand. To substantiate this claim, they provide a simple, easy-to-follow guideline for constructing universally quantified queries. >

Why not SQL!

Abstract The application of traditional database query languages, primarily the Structured Query Language SQL, for geographical information systems (GIS) and other non–standard database applications has been tried unsuccessfully; therefore, several extensions to the relational database query language SQL have been proposed to serve as a spatial query language. It is argued that the SQL framework is inappropriate for an interactive query language for a GIS and an extended SQL is at best a short term solution. Any spatial SQL dialect has a number of serious deficiencies, particularly the patches to incorporate the necessary spatial concepts into SQL.

Aspects of the automatic generation of SQL statements in a natural language query interface

In Natural Language Interfaces to databases it is currently a widely accepted technique to use an intermediate semantic representation of the NL sentences which is more or less based on First Order Predicate Logic, eventually augmented by some specific functions inherent to the database query language like, e.g. the aggregation functions of SQL. However, in order not to restrict the full power of NL one also has to augment the SQL language in some way, because SQL has some restrictions and shortcomings, of which the lack of a loop capability for handling ordinals (e.g. the 3rd lowest …, the 5th highest …) is the most serious. In this paper such an augmentation (which we call SQL +) is presented, and it is shown that—observing some simple rules—a NL sentence can be mapped from its internal representation to SQL + in a straightforward and uniform manner. Though these SQL + expressions may not always be optimal from a performance point of view, they have some advantages which we consider to be more useful.

Human factors study of two screen-oriented query languages: STBE and QBE

Summary-Table-By-Example (STBE) is a relational-calculus-based database query language. Like Query-by-Example (QBE), STBE is screen oriented and uses the example concept to formulate queries. The paper describes a series of experiments designed to evaluate the user-friendliness of STBE and QBE for relatively complex queries that use advanced features of both languages, and to propose possible improvements to STBE. The study, which used college students as subjects, investigated the differences between the retrieval features of both languages, and the types and frequencies of errors made. Some additional features to STBE are proposed as a result of this study.

Slice, chunk and dataflow anomaly as DATALOG rules

A chunk intuitively corresponds to the range of impact of a program change, and is defined as the union of those program slices impacted by the change. Given a chunk with respect to a program change, a maintenance programmer can consider the impact of the change without examining the entire program. Our definition of a chunk, along with the related debugging techniques slicing and detection of dataflow anomaly, is formulated as rules in DATALOG, a function-free logic-based data base query language. This formulation facilitates integration of these debugging aids into a uniform maintenance environment based on a knowledge-base system, and the concise and exact datalog rules also provide clear semantics to these debugging techniques.

TQuery: A context-sensitive temporal query language

Users of electronic medical databases request pertinent information by recasting their clinical questions into a formal database query language. Because the query language is the user's only access to the data, the query language must be powerful enough to enable users to express their data requirements. However, a competing need is for the query language to be restrictive enough so that queries can have unambiguous semantics and the query processor can generate correct answers. We describe a query language, called TQuery, that was designed specifically to formulate database queries that are dependent on temporal and contextual relationships. TQuery specifications express contextual constraints without the need to explicitly reference calendar dates. TQuery is the database query language used to retrieve patient data from an object-oriented electronic patient medical-record system called rhe temporal network (TNET). TNET and TQuery were developed to support the real-time temporal reasoning and representation needs of a LISP workstation-based medical expert system.

An approximate user-complexity measure for relational query language systems

Complexity theory provides a powerful methodology for evaluating the time and space requirements of algorithms. It would be helpful if a similar theory could be developed to analyze the level of difficulty presented to the user by database query languages. The relational database languages are of particular interest. Their power and flexibility have real potential for supporting the decision making needs of managers. In this paper an approximate user complexity measure is formulated and applied to three different experiments. These experiments measure user performance in the following tests: (1) relational algebra versus tuple calculus, (2) relational algebra versus domain calculus, and (3) relational algebra versus functional algebra. The results favor the procedural relational languages, and the approximate complexity measure constructed here parallels user performance.

A comparison between algebraic query languages for flat and nested databases

Recently, much attention has been paid to query languages for nested relations. In the present paper, we consider the nested algebra and the powerset algebra, and compare them both mutually as well as to the traditional flat algebra. We show that either nest or difference can be removed as a primitive operator in the powerset algebra. While the redundancy of the nest operator might have been expected, the same cannot be said of the difference. Basically, this result shows that the presence of one nonmonotonic operator suffices in the powerset algebra. As an interesting consequence of this result, the nested algebra without the difference remains complete in the sense of Bancilhon and Paredaens. Finally, we show there are both similarities and fundamental differences between the expressiveness of query languages for nested relations and that of their counterparts for flat relations.

Netlog: a logic query language for network model databases

A logic-based language for network model databases is presented. The language, called Netlog, provides support for navigating through objects while preserving the declarativity of logic programming. A formal definition of the network data model is presented along with a syntax and a declarative sematics of Netlog. The suitability of Netlog as a query language for CODASYL databases is then shown and an operational semantics, in terms of ordinary logic programs, is provided.

Database management and design

The use of a central repository for data and a database management system that enables programs to share data more efficiently and ensures the consistency of the data across the system is discussed. Relational databases, which represent both entities and relationships using tables, are described. It is shown that by proper design of the relational tables, the redundancy and wasted space of many ad hoc databases can be eliminated. Data are retrieved from a relational database through the use of a procedural query language. The leading query language for relational databases, the Structured Query Language (SQL), is examined. >

A simple characterization of uniform boundedness for a class of recursions

Detecting bounded recursions is a powerful optimization technique for recursive database query languages, as bounded recursions can be replaced by equivalent nonrecursive definitions. The problem is also of theoretical interest in that varying the class of recursions considered generates problem instances that vary from linearly decidable to NP-hard to undecidable. In this paper we review and clarify the existing definitions of boundedness. We then specify a class of recursions C such that membership in C guarantees that a certain simple condition is necessary and sufficient for boundedness. We use the notion of membership in C to unify and extend previous work on determining decidable classes of bounded recursions.

A fuzzy query language for relational databases

A fuzzy query language (FQL) for relational databases is proposed. FQL, constructed as an enhancement of the relational domain calculus, has sufficient capability to represent all four types of the fuzzy statements distinguished by the work of L.A. Zadeh (1978). The idea for constructing FQL is in the formulation of the fuzzy matching degrees that assigns the appropriate values in the interval to any combination of fuzzy queries and tuples in relational databases. FQL helps to provide a human-oriented interface to relational databases that store a vast amount of information. Furthermore, fuzzy expert systems are expected to be provided with the facility to make use of fact data in relational databases through FQL. In addition, FQL is a theoretical basis for systematically developing a higher human-oriented interface with relational databases.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Query optimization for nontraditional database applications

Database query languages and their use for programming nontraditional applications, such as engineering and artificial intelligence applications, are discussed. In such environments, database programs are used to code applications that work over large data sets residing in databases. Optimizing such programs then becomes a necessity. An examination is made of various optimization techniques, and transformations are suggested for improving the performance of database programs. These transformations result in new equivalent database programs with better space and time performance. Several of these techniques apply to classical query languages, although extended query languages which include an iteration operator are specifically discussed. >

Interaction with geographic information systems via spatial queries

In the past, the design of Geographic Information Systems (GIS) has been investigated in a bottom-up manner. At the same time, little consideration has been paid to those system components with which users have immediate contact such as languages to query spatial objects, or the user interface. Considerations about the interaction between the users and spatial data are of primary importance for these issues. The domain of this paper is the investigation of interactive spatial query languages that allow users to pose ad hoc queries against a geographic information system. Its motivation has been the observation that traditional database query languages are insufficient for the treatment of spatial properties. Deficiencies observed include the disregard of user concerns and the lack of support for renderings of query results in forms other than text. This paper presents a methodology for the design of interactive spatial query languages which are embedded into a human interface. The methodology is based upon the users' interactions with spatial objects, which are graphically rendered on a screen, and their pertinent operations. Objects and operations are provided at the conceptual level of the user interface and complemented by the selection of appropriate techniques to interact with spatial objects rendered on a screen. A number of spatial concepts are presented which are crucial for the design of a GIS query language. In a series of interface snapshots their incorporation into a human interface is presented, simulating the interaction between a user and a GIS.

Hypothetical datalog: complexity and expressibility

We present an extension of Horn-clause logic which can hypothetically add and delete tuples from a database. Such logics have been discussed in the literature, but their complexities and expressibilities have remained an open question. This paper examines two such logics in the function-free, predicate case. It is shown, in particular, that augmenting Horn-clause logic with hypothetical addition increases its data-complexity from PTIME to PSPACE. When deletions are added as well, complexity increases again, to EXPTIME. We then augment the logic with negation-as-failure and develop the notion of stratified hypothetical rulebases. It is shown that negation does not increase complexity. To establish expressibility, we view the logic as a query language for relational databases. It is shown that any typed generic query that is computable in PSPACE can be expressed as a stratified rulebase of hypothetical additions. Similarly, any typed generic query that is computable in EXPTIME can be expressed as a stratified rulebase of hypothetical additions and deletions. Neither of these results assumes the data domain is linearly ordered. In this way, we establish the expressive completeness of our logics for queries in PSPACE and EXPTIME, respectively.

IconicBrowser: An iconic retrieval system for object-oriented databases

From the point of view of the ability to manage complex data, object-oriented database systems are superior to conventional database systems. Query languages for object-oriented databases, however, tend to be overly complicated for the casual user unfamiliar with sophisticated database manipulation. This paper describes an IconicBrowser which allows the user to retrieve objects in a database by means of icons. Icons represent classes and objects in the database. Queries are specified by overlapping one icon over another. The system then interprets them into the database operations depending on their combination, and at the same time generates predicate-based (text-base) queries which can be used in other applications of the database.