Abstract: The use of classification and subsumption to process database queries is discussed. The data model, called CANDIDE, is essentially an extended version of the FL-1, KANDOR and BACK, frame-based knowledge representation languages. A novel feature of the approach is that the data-description language and data-manipulation language are identical, thus providing uniform treatment of data objects, query objects and view objects. The classification algorithm find the correct placement for a query object in a given object taxonomy. Tractability issues are explored, and the expressiveness of queries is compared with relational algebra. This data model has been implemented in POPLOG as the basis for a knowledge-base management system that includes an integrated natural-language query system. >

Abstract: Time consuming and reusable queries are handled in an object oriented database management system by providing a persistent stream object class. The persistent stream object class is a subclass of the stream class which is typically provided to encapsulate the results of a query. The persistent stream class inherits all the attributes and methods of the stream class but also includes a "save" method for saving the results of a query. When a query names a persistent stream as it object, the query results are saved. The query may also be performed in background or batch mode. All time consuming and reusable queries are performed by sending a query message to the persistent stream class, to thereby automatically save the query results.

Abstract: Strategies for secure query processing multilevel-security database management systems are proposed. They are carried out by query modification, a technique that has been used for enforcing integrity constraints and providing view mechanisms. The technique consists of replacing the query the user presents with one that, when evaluated, will perform the desired function. In the case of a view mechanism, the names of views referenced in the query are replaced by the definitions of the views in terms of base relations. The basic strategy and two variants-adding environmental information and using graphs-are described. The performance of the strategies is examined. >

Abstract: A resumeable batch query object class provides a link between a first dialog for obtaining information regarding a query to be performed by an object oriented database management system, a second dialog for manipulating the results of the query, and the stream which includes the query results. The resumeable batch query attributes include identifiers of the second dialog and the stream, and a method to run the query. The resumable batch query is used by the object oriented database management system to allow a second dialog to manipulate results of a batch or background query in the same manner as results of a foreground or interactive query. Time consuming queries may thereby be processed in background mode in a manner which is transparent to the second dialog.

Abstract: This article reports findings of empirical research that investigated information searchers' online query refinement process. Prior studies have recognized the information specialists' role in helping searchers articulate and refine queries. Using a semantic network and a Problem Behavior Graph to represent the online search process, our study revealed that searchers also refined their own queries in an online task environment. The information retrieval system played a passive role in assisting online query refinement, which was, however, or that confirmed Taylor's four-level query formulation model. Based on our empirical findings, we proposed using a process model to facilitate and improve query refinement in an online environment. We believe incorporating this model into retrieval systems can result in the design of more “intelligent” and useful information retrieval systems.

Abstract: Cyclic query processing issues in object-oriented databases are investigated. A data and cyclic query model is defined for an object-oriented database system, using a graph model. Then the efficient processing of a general object-oriented cyclic query is discussed. For efficient processing, a general cyclic query and the access plans generated for a given query are defined and a cost model is developed to determine the cost for each access plant generated. The retrieval algorithms used for actual data retrieval are also investigated. >

Abstract: It is desirable to answer queries posed to deductive databases by computing fixpoints because such computations are directly amenable to set-oriented fact processing. However, the classical fixpoint procedures based on bottom-up processing — the naive and semi-naive methods — are rather primitive and often inefficient. In this article, we rely on bottom-up meta-interpretation for formalizing a new fixpoint procedure that performs a different kind of reasoning: We specify a top-down query answering method, which we call the Backward Fixpoint Procedure. Then, we reconsider query evaluation methods for recursive databases. First, we show that the methods based on rewriting on the one hand, and the methods based on resolution on the other hand, implement the Backward Fixpoint Procedure. Second, we interpret the rewritings of the Alexander and Magic Set methods as specializations of the Backward Fixpoint Procedure. Finally, we argue that such a rewriting is also needed in a database context for implementing efficiently the resolution-based methods. Thus, the methods based on rewriting and the methods based on resolution implement the same top-down evaluation of the original database rules by means of auxiliary rules processed bottom-up.

Abstract: In this paper we present the design and initial performance results of a rule-based query optimizer used in Iris, an object-oriented database system [3]. Query optimization methods are expressed as rules and the entire query process is carried out in a way analogous to the operation of production systems in AI. Two kinds of rules are used: the first kind transform a query, represented as a relational algebra expression, into an equivalent, but simpler, query; the second kind add information to the relational algebra representation to specify join order and data access methods. Preliminary results show that the speed of the query optimizer and the performance of the execution plans generated are comparable to those in a traditional relational database system.

Abstract: We define an object-oriented knowledge base to be a deductive knowledge base that is based on an object model. One of the major advantages provided by object-oriented knowledge bases is that the first order language used for object description can be used as a query language as well. Since object-dependent procedures are included in this framework, the problem of query processing is nontrivial. On one hand some attributes involved in a query need to be derived from a procedure and constrained by some other relations, and therefore combinatorial explosion may occur; on the other hand a query may be specified in an improper order such that the search space becomes intolerable large. In this paper we first describe two approaches to optimize the query evaluation process: the semantic optimization approach and the conjuct reordering approach. Next, we examine the problem of logical query processing when an object-oriented knowledge base is built on a relational database such as Ingres.

Abstract: 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. The authors 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 operations are formally defined from both a syntactic and a semantic point of view. >

Abstract: The use of data abstraction in object-oriented databases places a burden on the ability of the system to perform query optimization. A framework for query specification and optimization is discussed that is applicable to object-oriented database systems that take a strict view of data abstraction. Techniques that preserve much of the optimization potential of relational languages by limiting the query language are examined. Techniques are given for query optimization that involve type-specific rewrite rules. >

Abstract: Maintaining the closure property is an important database language design objective. Queries issued in a query language that possesses this property return results that are structured and modeled by the same data model for which the query language is designed. A useful consequence of this is that the result of a query can be uniformly operated on by other queries (i.e., using the same language constructs). None of the existing query languages that have been designed for the class of object-oriented data models possesses the closure property. In this dissertation, we introduce a new query model for object-oriented databases in which this property is preserved. Furthermore, we make our query model concrete by introducing an object-oriented query language named OQL as an example of this query model. A query in this language returns a subdatabase whose structure consists of some selected object classes and their associations. The objects that fall in the patterns of object associations specified in the query constitute the extension of the resulting subdatabase. In this dissertation, we also introduce a knowledge definition language for defining deductive rules and integrity constraints pertaining to an object-oriented database. Deductive rules in this language derive new patterns of associations among objects based on existing and/or other derived patterns. Deductive reasoning about a large number of objects stored in a database is a needed functionality in several new database application domains (e.g., CAD/CAM databases). The OQL and the knowledge definition language are tightly coupled. This facilitates the integration of concepts and techniques, which are typically found in different categories of systems such as database management systems and expert systems, into one integrated, object-oriented knowledge base management system (OKBMS) that meets the specifications and requirements of the new database application domains.

Abstract: Query languages have become increasingly important as comprehensive medical databases have become a part of the available knowledge base for patient care. As the user community expands and the need for bedside query arises, the requirement for a fast, easy-to-use, interactive query system must be met. This paper describes the evolution of a query language for the TMR database, discusses problems and limitations of the system, and proposes new approaches to the problem.

Abstract: This paper presents a graphical query language for semantic data models. This language is based on a generic semantic model. It is integrated in the CANDID system, which is a graphical interface fur the manipulation of databases. Any schema is represented by a graph divided into families of object types. The graphical query language makes it possible to express a request by describing with a graph an object solution of the request. A request is sometimes expressed in several stages. A stage corresponds to the expression of a simpler subrequest. This language is also characterized by the absence of boolean operators and quantifiers, which are replaced by manipulations on Venn diagrams. Since a request in fact defines derived elements, almost all of a request can be incorporated into the schema. CANDID has been designed to be adapted to any DBMS which has deduction mechanisms.

Abstract: A scheme that attempts to efficiently store and retrieve execution plans for generalized queries is proposed. The overhead of the scheme is insignificantly low. The scheme uses query graphs to represent a query. Each query graph is converted to a standardized tree which in turn is represented in a canonical vector form. The execution plan is then stored against this vector. It is concluded that the proposed technique can improve database system performance by using strategy databases. >

Abstract: A prototype expert visual query system (X-VIQU) for accessing multiple databases, particularly for unskilled users, is presented. The combination of an expert system and a graphical representation of the query paths, as well as of a corresponding hierarchical level in the database, facilitates information retrieval, particularly when multiple databases must be accessed. An example of the query process is provided to illustrate the operating principles of X-VIQU. >

Abstract: This work discusses a method for the semantic description of project results through the aid of a user definable faceted classification system. Project results of previously carried out projects, e.g. concepts, control systems or pieces of real time software are catalogued in this classification scheme via a descriptor, which serves as contentual representation for them. The method of ‘Descriptive Search’ is based on the comparison of a search descriptor, given by the user in a search query, with the actual descriptors of the catalogued projects. By the evaluation of a similarity measure the comparison of the search descriptor with the existing project descriptors leads to a list of project results, which is ranked according to relevance to the search query. With this method not only a separation of relevant results from irrelevant ones is achieved, but also a ranking of the relevant results with respect to the degree of similarity to the search query.

Abstract: Two issues in retrieval from a database are addressed: effectiveness and efficiency. Effectiveness is concerned with the representation of answers; and efficiency is concerned with fast response to queries. Conventional responses to queries in database systems, usually consisting of lists of tuples, do not necessarily provide effective communication between a user and the system. The first part of this thesis suggests how, when responding to a user query, the system can improve effectiveness of information transfer by providing concise intensional answers, as a set of concepts and predicates, rather than just providing the set of facts satisfying the query. Abstracting responses before presenting them to the user is an effective means of information exchange. Aggregation is a commonly used abstraction process. The second part of this thesis investigates aggregate responses that are expressions of quantified concepts. The tradeoff between the conciseness and impreciseness of an aggregate response is studied. Conciseness is measured by the length of the expression and preciseness is measured by the entropy of the expression. The objective of conventional query optimization is usually to minimize the total time required for evaluating a query. The last part of this thesis argues that in some interactive environment, the initial response time of a query may also be considered important. For selection queries, a long initial response time can be shortened without compromising on the total time for completely evaluating a query. The same, however, is not always true for join queries. But the tradeoffs between the total response time and the initial response time of a query are quantifiable. Semantic query optimization techniques can also improve the initial response time of a query. Moreover, in addition to exact rules, inexact rules can be utilized to improve the initial response time.

Abstract: 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 & Kibler, 1984; Williams, 1984; Ogden, Korenshtein, & 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.

Abstract: Abstract The collective processing of multiple queries in a database system has recently received renewed attention due to its capability of improving the overall performance of a database system and its applicability to the design of knowledge-based expert systems and extensible database systems. A new multiple query processing strategy is presented which utilizes semantic knowledge on data integrity and information on predicate conditions of the access paths (plans) of queries. The processing of multiple queries is accomplished by the utilization of subset relationships between intermediate results of query executions, which are inferred employing both semantic and logical information. Given a set of fixed order access plans, the A ∗ algorithm is used to find the set of reformulated access plans which is optimal for a given collection of semantic knowledge.

Abstract: Graphical Direct Manipulation (GrDM) query languages are characterized and positioned with respect to traditional textual query languages. After a brief survey of the current state of the art, the Pasta-3 GrDM query language is presented, with emphasis on three features that make significant new contributions to this field: (1) its GrDM basis (query editing through clicking and dragging of an iconic representation of the query expression), (2) its cooperative environment (handy values, automatic path completion, edit-and-reevaluate loop), and (3) its expressive power (arbitrarily complex conditions, recursive queries, logical variables and quantification, subqueries, mixing in Prolog code). Several examples taken directly from the nearly complete implementation are discussed in detail.

Abstract: This paper presents a query language, QPF, and describes its implementation in a knowledge-based geographical information system (KGIS). Using QPF, users can retrieve both symbolic and graphical data, and browse through the entire database without prior knowledge of the contents and organization of the KGIS. Processing of complex queries, such as query by object spatial relations, is guided by knowledge represented in frames that simplifies not only query processing, but also query definition and makes querying user-friendly.