Showing papers on "Graph database published in 1984"

On compiling queries in recursive first-order databases

Abstract: A first-order database ~s defined as a function-free first-order theory in which the ground units serve as the extensional database and the proper noniogical axioms serve as the intensional database. The following problem is addressed: \"Given a recurswe nonlogical axiom and the form of a potential query, can one describe a set of database retrieval requests that gives the correct answers and is guaranteed to terminate.\" The solution uses resolution-proof techmques over connection graphs to derive a program of relational database operations that gives all the answers to a query and has a welldefined termmatton condiUon.

Optimization of Nested Queries in a Distributed Relational Database

Abstract: This paper describes how nested queries in the SQL language are processed by R*, an experimental adaptation to the distributed environment of the well-known centralized relational DBMS, System R Nested queries are queries in which a predicate references the result of another query block (SELECTFROMWHERE), called a subquery block (subQB) SubQBs may themselves contain one or more subQBs Depending upon whether a subQB references values in other query blocks, it is processed differently, as either an Evaluate-at-Open or Evaluate-at-Application subQB type Three tasks comprise execution of each query block: initiation, evaluation, and application When the query’s tables are distributed among multiple sites, optimization of nested queries requires determining for each subQB: the site to perform each task, the protocols controlling interactions between those tasks, and the costs of each option, so that a minimal-cost plan can be chosen R* optimizes each query block independently, “bottom up”, using only the cost, cardinal&y, and result site of the subQB in the optimization of its containing query block

Line Graph of Gamma-Acyclic Database Schems and its Recognition Algorithm

Abstract: In this paper the properties of the line graph of y-aeyclic hyperg-raphs are described. Based on the properties, an efficient algorithm is given for determining whether a hypergraph is γ-acyclic. The algorithm runs in 0(n(n+e)) time for a hypergraph with its line graph having n vertices and e edges.

Interpretation of natural language database queries using optimization methods (linguistics)

Abstract: The automatic interpretation of natural language (in this work, English), database questions formulated by a user untrained in the technical aspects of database querying is an established problem in the field of artificial intelligence. State-of-the-art approaches involve the analysis of queries with syntactic and semantic grammars expressed in phrase structure grammar or transition network formalisms. With such methods difficulties exist with the detection and resolution of ambiguity, with the mis-interpretation possibilities inherent with finite length look-ahead, and with the modification and extension of a mechanism for other sources of semantic knowledge. This work examines the potential of optimization techniques to solve these problems and interpret natural language, database queries. The proposed method involves developing a 0-1 integer programming problem for each query. The possible values that the set of variables in the optimization may take on is an enumeration of possible such individual associations between the database schema and the query. The solution to the integer programming problem corresponds to a single assignment of database data items and relationships to the words in the query. Constraints are derived from syntactic and database schema knowledge stored as libraries of templates. An objective function is used to rank the possible associations as to their likelihood of agreement with the intent of the questioner. A test mechanism was built to support evaluation of the proposed method. Suitable knowledge source template sets and an objective function were developed experimentally with the test mechanism from a learning sample of queries. Then the performance of the method was compared to that of an established system (PLANES) on a test set of queries. The performance of the new method was found to be comparable to that of the established system.

Optimal graph clustering problems with applications to information system design

Abstract: Information system design problems, including database and software, can often be represented in terms of directed or undirected graphs. Some of these problems typically involve determining how to cut the graph into a set of nonvoid and disjoint subgraphs such that each of the subgraphs is of a limited weight and belongs to a graph class while an objective function defined over the subgraphs is optimized. The class of information system design problems is analyzed with the following three objectives: First, to formally define this class of problems as an Optimal Graph Clustering (OGC) problem and classify it into a set of subproblems. Second, to find efficient algorithms that give an exact and optimal solution to each subproblem with nontrivial objective function and constraints. An third, to demonstrate these algorithms' usefulness by formalizing and solving some information system (database and software) design problems. Eight classes of digraphs (general digraph, acyclic digraph, out-necklace, out-tree, out-star, in-necklace, in-tree and in-star) and four classes of undirected graphs (general undirected graph, necklace, tree and star) are considered and are used to classify the OGC problem into thirty-five subproblems. These subproblems are shown to be NP-complete problems. Sequential clustering technique and maximal clusterings enumeration are used to show those OGC subproblems with given graphs that have n vertices and n-1 arcs or n arcs can be solved in pseudopolynomial time. It is also determined that for the other NP-complete problems, if the graphs are sparse (i.e., the number of arcs does not exceed the number of vertices greatly) they are solvable by computer. The class of possible objective functions and constraints applicable to these solutions such that all time complexities remain the same is also defined. All monotonic objective functions and constant time computable constraints are found to be applicable. The solutions' usefulness is demonstrated by solving three information system design problems: B-tree secondary storage allocation, translation of an integrated schema into a hierarchial schema, and database record clustering.