Translational Semantics for a Conceptual Level Query Language

A conceptual level database language for the entity relationship (ER) model implicitly contains integrities basic to ER concepts and special retrieval semantics for inheritances of attributes and relationships.Prolog,which belongs to the logical and physical level,cannot be used as a foundation to directly define the database language.It is shown how Prolog can be enhanced to understand the concepts of entities,relationships,attributes and is-a relationships.The enhanced Prolog is then used as a foundation to define the semantics of a database query language for the ER model.The three basic functions of model specification,updates and retrievals are defined.     

Emergent semantics through interaction in image databases

In this paper, we briefly discuss some aspects of image semantics and the role that it plays for the design of image databases. We argue that images don't have an intrinsic meaning, but that they are endowed with a meaning by placing them in the context of other images and by the user interaction. From this observation, we conclude that, in an image, database users should be allowed to manipulate not only the individual images, but also the relation between them. We present an interface model based on the manipulation of configurations of images     

Children and databases: an analysis of data entry and query formulation

Abstract This study was undertaken, in part, to analyse the means by which primary children familiarized themselves with a large database. Their approaches to the problems of coding data for entry were studied and the types of error and frequency of occurrence were recorded. Query formulation was studied in parallel with data entry, particularly the difficulties presented by the correct expression of queries, choice of tests and use of coded fields. Attention was paid to the age and sex of the children for both aspects of the study.     

A Fixpoint Semantics for Stratified Databases

Przmusinski extended the notion of stratified logic programs,developed by Apt,Blair and Walker,and by van Gelder,to stratified databases that allow both negative premises and disjunctive consequents.However,he did not provide a fixpoint theory for such class of databases.On the other hand,although a fixpoint semantics has been developed by Minker and Rajasekar for non-Horn logic programs,it is tantamount to traditional minimal model semantics which is not sufficient to capture the intended meaning of negation in the premises of clauses in stratified databases.In this paper,a fixpoint approach to stratified databases is developed,which corresponds with the perfect model semantics.Moreover,algorithms are proposed for computing the set of perfect models of a stratified database.     

Modification semantics in now-relative databases

Most real-world databases record time-varying information. In such databases, the notion of “the current time,” or NOW, occurs naturally and prominently. For example, when capturing the past states of a relation using begin and end time columns, tuples that are part of the current state have some past time as their begin time and NOW as their end time. While the semantics of such variable databases has been described in detail and is well understood, the modification of variable databases remains unexplored. This paper defines the semantics of modifications involving the variable NOW. More specifically, the problems with modifications in the presence of NOW are explored, illustrating that the main problems are with modifications of tuples that reach into the future. The paper defines the semantics of modifications—including insertions, deletions, and updates—of databases without NOW, with NOW, and with values of the type NOW+Δ, where Δ is a non-variable time duration. To accommodate these semantics, three new timestamp values are introduced. Finally, implementation is explored. We show how to represent the variable NOW with columns of standard SQL data types and give a mapping from SQL on NOW-relative data to standard SQL on these columns. The paper thereby completes the semantics, the querying, and the modification of now-relative databases.     

Logic-based query optimization for object databases

We present a technique for transferring query optimization techniques, developed for relational databases, into object databases. We demonstrate this technique for ODMG database schemas defined in ODL and object queries expressed in OQL. The object schema is represented using a logical representation (Datalog). Semantic knowledge about the object data model, e.g., class hierarchy information, relationship between objects, etc., as well as semantic knowledge about a particular schema and application domain are expressed as integrity constraints. An OQL object query is represented as a logic query and query optimization is performed in the Datalog representation. We obtain equivalent (optimized) logic queries, and subsequently obtain equivalent (optimized) OQL queries for each equivalent logic query. We present one optimization technique for semantic query optimization (SQO) based on the residue technique of U. Charavarthy et al. (1990; 1986; 1988). We show that our technique generalizes previous research on SQO for object databases. We handle a large class of OQL queries, including queries with constructors and methods. We demonstrate how SQO can be used to eliminate queries which contain contradictions and simplify queries, e.g., by eliminating joins, or by reducing the access scope for evaluating a query to some specific subclass(es). We also demonstrate how the definition of a method or integrity constraints describing the method, can be used in optimizing a query with a method     

A query algebra for program databases

Querying source code is an essential aspect of a variety of software engineering tasks such as program understanding, reverse engineering, program structure analysis and program flow analysis. In this paper, we present and demonstrate the use of an algebraic source code query technique that blends expressive power with query compactness. The query framework of Source Code Algebra (SCA) permits users to express complex source code queries and views as algebraic expressions. Queries are expressed on an extensible, object-oriented database that stores program source code. The SCA algebraic approach offers multiple benefits such as an applicative query language, high expressive power, seamless handling of structural and flow information, clean formalism and potential for query optimization. We present a case study where SCA expressions are used to query a program in terms of program organization, resource flow, control flow, metrics and syntactic structure. Our experience with an SCA-based prototype query processor indicates that an algebraic approach to source code queries combines the benefits of expressive power and compact query formulation     

First-order query rewriting for inconsistent databases

We consider the problem of retrieving consistent answers over databases that might be inconsistent with respect to a set of integrity constraints. In particular, we concentrate on sets of constraints that consist of key dependencies, and we give an algorithm that computes the consistent answers for a large and practical class of conjunctive queries. Given a query q, the algorithm returns a first-order query Q (called a query rewriting) such that for every (potentially inconsistent) database I, the consistent answers for q can be obtained by evaluating Q directly on I.     

Content-based query processing for video databases

This paper presents a query processing strategy for the content-based video query language named CVQL. By CVQL, users can flexibly specify query predicates by the spatial and temporal relationships of the content objects. The query processing strategy evaluates the predicates and returns qualified videos or frames as results. Before the evaluation of the predicates, a preprocessing is performed to avoid unnecessary accessing of videos which are impossible to be the answers. The preprocessing checks the existence of the content objects specified in the predicates to eliminate unqualified videos. For the evaluation of the predicates, an M-index is designed based on the analysis of the behaviors of the content objects. The M-index is employed to avoid frame-by-frame evaluation of the predicates. Experimental results are presented to illustrate the performance of this approach     

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     

On the partial semantics for disjunctive deductive databases

Partial stable models for deductive databases, i.e., normal function-free logic programs (also called datalog programs), have two equivalent definitions: one based on 3-valued logics and another based on the notion of unfounded set. The notion of partial stable model has been extended to disjunctive deductive databases using 3-valued logics. In this paper, a characterization of partial stable models for disjunctive datalog programs is given using a suitable extension of the notion of unfounded set. Two interesting sub-classes of partial stable models, M-stable (Maximal-stable) (also called regular models, preferred extension,and maximal stable classes) and L-stable (Least undefined-stable) models, are then extended from normal to disjunctive datalog programs. On the one hand, L-stable models are shown to be the natural relaxation of the notion of total stable model; on the other hand the less strict M-stable models, endowed with a nice modularity property, may be appealing from the programming and computational point of view. M-stable and L-stable models are also compared with the regular models for disjunctive datalog programs recently proposed in the literature.     

A possible world semantics for disjunctive databases

The fundamental problem that arises when a ground atom in a disjunctive database is assumed false is discussed. There are basically two different approaches for inferring negative information for disjunctive databases: J. Minker's (1982) generalized closed world assumption (GCWA) and K.A. Ross and R.W. Topor's (1988) disjunctive database rule (DDR). It is argued that neither approach is satisfactory. A database semantics called PWS is proposed. It is shown that for propositional databases with no negative clauses, the problem of determining if a negative ground literal is inferred under the GCWA is co-NP-hard, while the same problem can be solved efficiently under the DDR and PWS. However, in the general case, the problem becomes co-NP-complete for the DDR and PWS. Relationships among GCWA, DDR, and PWS are highlighted. In general, disjunctive clauses are interpreted inclusively under the DDR and unpredictably under the GCWA     

Rule-based spatiotemporal query processing for video databases

In our earlier work, we proposed an architecture for a Web-based video database management system (VDBMS) providing an integrated support for spatiotemporal and semantic queries. In this paper, we focus on the task of spatiotemporal query processing and also propose an SQL-like video query language that has the capability to handle a broad range of spatiotemporal queries. The language is rule-based in that it allows users to express spatial conditions in terms of Prolog-type predicates. Spatiotemporal query processing is carried out in three main stages: query recognition, query decomposition, and query execution.Received: 11 October 2001, Accepted: 3 October 2003, Published online: 12 December 2003Edited by: A. Buchmann Correspondence to: Özgür UlusoyThis work is supported by the Scientific and Research Council of Turkey (TÜBITAK) under Project Code 199E025. This work was done while the first author was at Bilkent University.     

MyBenchmark: generating databases for query workloads

To evaluate the performance of database applications and database management systems (DBMSs), we usually execute workloads of queries on generated databases of different sizes and then benchmark various measures such as respond time and throughput. This paper introduces MyBenchmark, a parallel data generation tool that takes a set of queries as input and generates database instances. Users of MyBenchmark can control the characteristics of the generated data as well as the characteristics of the resulting workload. Applications of MyBenchmark include DBMS testing, database application testing, and application-driven benchmarking. In this paper, we present the architecture and the implementation algorithms of MyBenchmark. Experimental results show that MyBenchmark is able to generate workload-aware databases for a variety of workloads including query workloads extracted from TPC-C, TPC-E, TPC-H, and TPC-W benchmarks.     

A graphical query language for simulation databases

In this paper we propose a graphical query language to analyse simulation runs which are stored in databases with a temporal dimension. A simulation run is a sequence of system states produced by discrete simulation. It may become very large, such that manual analysis based on database browsing is no longer feasible. Hence simulation databases require a specific query language to analyse the simulation data. Queries may be related to single states (e.g. Is there a state where condition c1 holds? ) or to state sequences (e.g. Is there a state sequence, where first c1 holds, then c2 and finally c3? ).An existing Petri net simulation environment has been extended to support the described concepts.     

面向外包空间数据库的范围查询验证

针对空间范围查询验证方法（例如VR-tree和MR-tree）普遍存在验证对象（VO）中包含大量的节点验证信息,造成服务器到客户端的传输代价较大以及客户端验证效率较低等问题,提出一种新的验证索引结构（ADS）MGR-tree。首先利用拆分思想,通过在Grid-tree的叶子节点中嵌入R-tree,并结合Merkle哈希树的验证方法,极大地减小VO的大小,提高查询和验证的效率。在此基础上,利用Hilbert曲线降维的特性,构建了优化的索引结构MHGR-tree,并提出一种过滤策略,进一步提高验证的效率。实验结果表明,所提方法具有更好的表现。在最好情况下,MHGR的VO大小和验证时间仅为MR的63%和19%。     

Typed query languages for databases containing queries

This paper introduces and studies the relational meta algebra, a statically typed extension of the relational algebra to allow for meta programming in databases. In this meta algebra one can manipulate database relations involving not only stored data values (as in classical relational databases) but also stored relational algebra expressions. Topics discussed include modeling of advanced database applications involving “procedural data” ; desirability as well as limitations of a strict typing discipline in this context; equivalence with a first-order calculus; and global expressive power and non-redundancy of the proposed formalism.     

Fast query processing in deductive databases

A special-purpose algorithm, that analyzes the structure of a recursion and exploits its properties in query processing in a deductive database is presented. This method is applied to linear rules, a large and common class of recursion. The structural approach to rule processing (SARP) prototype system that implements the algorithm is described     

Skyline-join query processing in distributed databases

The skyline-join operator, as an important variant of skylines, plays an important role in multi-criteria decision making problems. However, as the data scale increases, previous methods of skyline-join queries cannot be applied to new applications. Therefore, in this paper, it is the first attempt to propose a scalable method to process skyline-join queries in distributed databases. First, a tailored distributed framework is presented to facilitate the computation of skyline-join queries. Second, the distributed skyline-join query algorithm (DSJQ) is designed to process skyline-join queries. DSJQ contains two phases. In the first phase, two filtering strategies are used to filter out unpromising tuples from the original tables. The remaining tuples are transmitted to the corresponding data nodes according a partition function, which can guarantee that the tuples with the same join value are transferred to the same node. In the second phase, we design a scheduling plan based on rotations to calculate the final skyline-join result. The scheduling plan can ensure that calculations are equally assigned to all the data nodes, and the calculations on each data node can be processed in parallel without creating a bottleneck node. Finally, the effectiveness of DSJQ is evaluated through a series of experiments.