I.F. Cruz, A.O. Mendelzon, P.T. Wood, "A Graphical Query Language Supporting Recursion", SIGMOD Record Vol 16, Issue 3, 1987.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....[TR 95a, AB 97, TR 95b] provide a detailed account of the TRANSIMS project. Regular expression constrained simple path problems were considered by Mendelzon and Wood [MW95] The authors investigate this problem in the context of nding ecient algorithms for processing database queries (see [CMW87, CMW88, MW95]) A recent paper by Abiteboul and Vianu describes further results on related problems [AV99] Yannakakis [Ya90] in his keynote talk has independently outlined some of the polynomial time algorithms given in Section 5. Romeuf [Ro88] also independently considered some of the problems discussed in ....

M. Cruz, A. Mendelzon and P. Wood, A graphical query language supporting recursion, Proc. 9th ACM SIGMOD Conference on Management of Data, San Francisco, CA, 1990, 1987, pp. 323-330.

....hierarchies of a schema diagram. In comparison, let the inter object relationship between classes, traditionally called the relationship instance, specifies the functional mapping from the set of objects in one class to the set of objects in the other. However, many existing visual query languages[2, 7, 10, 11, 13, 14, 24, 26, 28] adopted graphs to enhance intuitive understanding of structural relationships between classes. They represent queries just by attaching conditions to a sub graph of the schema diagram without expressing the implication of inter object relationships between the related classes in order to ....

....They represent queries just by attaching conditions to a sub graph of the schema diagram without expressing the implication of inter object relationships between the related classes in order to represent path expressions properly. In fact, the graph based query languages such as QBD [2] G [10], ERC[11] and GRAQULA[26] are based on relational or entity relationship (ER) models. Even though these visual query languages and their simple extensions may 2 simulate the notion of path expressions by valued based joining without the notion of object identity[1, 5, 18] they fail to support ....

Cruz, I., Mendelzon, A., and Wood, P., "A Graphical Query Language Supporting Recursion, " In Proc. ACM SIGMOD Int'l Conf. on Management of Data, pages 323--330, 1987.

.... expressive power of query languages was very fashionable at that time, especially because of Datalog growth [57] and graphical query languages with high expressive power were mainly proposed by Alberto Mendelzon s group at the University of Toronto (they were then working on the G language [31]) We extended QBD for transitive closure to be graphically expressed [3] and decided to compare its expressive power to G . We did not have e mail (I know it is hard to believe, but this happened approximately ten years ago) so I wrote a real letter to Alberto. It was however one of his ....

I.F.Cruz, A.O.Mendelzon, and P.T.Wood. A graphical query language supporting recursion. In Proceedings of the ACM SIGMOD Conf. on Management of Data, San Francisco, USA, pp. 323-330, ACM Press (1987).

....6. RELATED WORK One of the first graphical display systems for databases was the Spatial Data Mangement System [13] An early browsing by navigation implementation was the entity based interface presented in [6] Several other graphical interfaces for databases have been developed since then [3 5, 7 11, 14, 15, 18, 21, 24, 27 33]. A toolkit for designing graphics based interfaces for object oriented databases has been described in [16] The design of OdeView was directly influenced by SIG [20] a system for generating displays of complex objects. In SIG, associated with a class of objects is a display type, which is ....

I. F. Cruz, A. O. Mendelzon and P. T. Wood, "A Graphical Query Language Supporting Recursion", Proc. ACM SIGMOD Conf. on Management of Data, 1986, 16-52.

....and edge labels are used to select walks in the hypertext graph. An outline of the application of this model and its query language to the implementation of hypertext documents is given by using an extended example of a travel agency application. 1 Introduction Recent database research work [7, 8, 11, 4, 16] shows a growing interest in the definition of graph models and languages to allow a natural way of handling data appearing in applications such as hypertext [6, 3] or geographic database [10] systems. Standard data models are often inefficient as they do not capture the inherent structure of data ....

....[15] over data types are used to select walks in a graph. For example the regular expression JOURNEY first (STOP next) STOP in CITY describes the walks going from a journey node (a node of type JOURNEY ) to one of its stops in a city (node of type CITY ) Our language is a variant of GraphLog [7, 8], in which regular expressions are also used for specifying paths in a graph. One main difference between GraphLog and our approach is that the former presents a graphical query language while we offer an algebraic language on regular expressions over types. To illustrate the power of this ....

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I.F. Cruz, A.O. Mendelzon, and P.T. Wood. A graphical query language supporting recursion. In Proc. of the ACM SIGMOD Conf. on Management of Data, pages 323--330, San Francisco, 1987.

....for the rewriting of regular expressions apply also to the case of regular path queries. 1 Introduction Database research has often shown strong interest in path queries, i.e. queries that ask for all pairs of objects in the database that are connected by a speci ed path (see for example [CMW87, CM90] Recent work on semi structured data has revitalized such interest. Semi structured data are data whose structure is irregular, partially known, or subject to frequent changes [Abi97] They are usually formalized in terms of labeled graphs, and capture data as found in many application ....

I. F. Cruz, A. O. Mendelzon, and P. T. Wood. A graphical query language supporting recursion. In Proc. of the ACM SIGMOD Int. Conf. on Management of Data, pages 323-330, San Francisco (CA, USA), 1987.

....for the rewriting of regular expressions apply also to the case of regular path queries. 1 Introduction Database research has often shown strong interest in path queries, i.e. queries that ask for all pairs of objects in the database that are connected by a speci ed path (see for example [13, 12]) Recent work on semi structured data has revitalized such interest. Semi structured data are data whose structure is irregular, partially known, or subject to frequent changes [1] They are usually formalized in terms of labeled graphs, and capture data as found in many application areas, such ....

I. F. Cruz, A. O. Mendelzon, and P. T. Wood. A graphical query language supporting recursion. In Proc. of the ACM SIGMOD Int. Conf. on Management of Data, pages 323-330, San Francisco (CA, USA), 1987.

....equivalent to the query stage of STRUQL a but unlike STRUQL a LOREL, cannot construct a new output graph. This feature is strictly necessary in our application. Compared to UnQL [BUN 96] which can also construct new graphs, the construction part of STRUQL is more powerful, as explained above. G [CRU 87, CRU 88, WOO 88] is also a query language for graphs with regular path expressions, graph construction, and active domain semantics: the graph construction part of G corresponds to the restriction of STRUQL to unary Skolem functions. 3.1. Example Web Site The following example shows how for one ....

Cruz I., A.O.Mendelson, P.T.Wood, "A graphical query language supporting recursion ". In Proceedings of ACM SIGMOD Conf., 1987.

.... data model has also been used, two ways for representing graphs in this model are mentioned in [Rose86] In most proposals the authors do not really care how graphs are represented but just focus on the abstract graph structure and the study of interesting operations or traversal techniques [CrMW87a, CrMW87b, CrN89, Rose86]. In all of these approaches there is no explicit modeling of graphs within a general database environment and therefore no problem of integration with the data model. As far as queries are concerned, two main strategies are to offer general purpose facilities that allow to express graph traversal ....

....[Ag87, Rose86, CrN89] BiRS90] propose an SQL extension based on the idea to generate a set of paths in the from clause from which interesting paths are selected (with the help of special operators) and then projected into a relation again. An entirely different style of querying is suggested in [CrMW87a, CrMW87b, CoM90, CoM93]) The idea is to formulate a query as a set of graphs which are viewed as patterns (edges in patterns may be regular expressions over edge labels) all subgraphs of the database instance are returned matching these patterns. Since in all of this work the assumption is that graphs are represented ....

Cruz, I.F., A.O. Mendelzon, and P.T. Wood, A Graphical Query Language Supporting Recursion. Proc. SIGMOD Conf. 1987, 323-330.

....with the signature and the optimization rules. In contrast, in PL type systems, the semantics are always included in the definition of entities such as types, polymorphic functions, type operators, etc. Graph based data models which may be compared to GraphDB have been proposed, for example, by [CMW 87, Agra 87, BRS 90, ErG 94, GPVV 94, KSW 95] Since the purpose of this paper is not to propose a data model but rather to offer an SOS specification of the given model GraphDB, we do not discuss these models here, see [G ti 94a, G ti 94b] Object oriented query algebras can be found, for example, ....

Cruz, I.F., A.O. Mendelzon, and P.T. Wood, A Graphical Query Language Supporting Recursion. Proc. ACM SIGMOD 1987, 323 - 330.

.... graphs can be modeled implicitly in terms of the usual features of a given data model, e.g. the relational model [Kung86, StR86, Ag87, BiRS90] or a functional model [Rose86] In most proposals the authors do not really care how graphs are represented but just focus on the abstract graph structure [CrMW87a, CrMW87b, CrN89, Rose86]. For querying, two main strategies are to offer general purpose facilities that allow to express graph traversal problems (like recursion, iteration) Rose86, StR86] or to offer special operators [Ag87, Rose86, CrN89] BiRS90] propose an SQL extension based on the idea to generate a set of ....

....that allow to express graph traversal problems (like recursion, iteration) Rose86, StR86] or to offer special operators [Ag87, Rose86, CrN89] BiRS90] propose an SQL extension based on the idea to generate a set of paths in the from clause from which interesting paths are selected. In [CrMW87a, CrMW87b, CoM90, CoM93] the idea is to formulate a query as a set of graphs which are viewed as patterns; all subgraphs of the database instance are returned matching these patterns. In all of these approaches there is no explicit modeling of graphs within a general database environment and therefore no problem of ....

Cruz, I.F., A.O. Mendelzon, and P.T. Wood, A Graphical Query Language Supporting Recursion. Proc. SIGMOD Conf. 1987, 323-330.

....The output of GVISUAL and GOQL queries is more general than frame sequences, and queries may return presentation paths, graphs, sets of video objects, etc. Graphs in databases have been used by different researchers in different contexts. In the database query and visualization system G [CMW 87, CMW 88] and Hy [CM 90, CM 93] the database is visualized as a graph, and a query is formulated as a set of graphs which are viewed as patterns to be matched against the database. In the Graph Oriented Object Database model [GPV 90a, GPV 90b, GBPV 94] the emphasis is on representing the ....

Cruz, I.F., Mendelzon, A., Wood, P.T., " A Graphical Query Language Supporting Recursion", ACM SIGMOD Conference, 1987.

....of StruQL is similar to LOREL [QRS 95] but unlike LOREL, StruQL can construct a new output graph. This feature is strictly necessary in our application. Compared to UnQL [BDHS96] which can also construct new graphs, the construction part of StruQL is more powerful, as explained above. G [CMW87, CMW88, Woo88] is also a query language for graphs with regular path expressions, graph construction, and active domain semantics: the graph construction part of G corresponds to the restriction of StruQL to unary Skolem functions. 3 Query Evaluation and Optimization A naive evaluation strategy ....

I. Cruz, A.O. Mendelzon, and P.T Wood. A graphical query language supporting recursion. In Proceedings of ACM SIGMOD Conf., San Francisco, California, May 1987.

....combines the use of the hygraph visual formalism with visual queries expressed as hygraph patterns. The notion of resorting to patterns as a visual notation to describe queries has a popular predecesor in QBE, while the more closely related idea of resorting to graph patterns originates in G [CMW87, CMW88] The visual queries supported by Hy are expressions of the GraphLog query language [Con89, CM90b] suitably extended to hygraphs. GraphLog queries are hygraphs whose nodes are labeled by sequences of terms, and whose edges and blobs are labeled by path regular expressions on relations. ....

....visually, the areas of visual languages and visual programming are closely related to the work presented in the thesis. Concerning visual query languages in particular, a survey of visual query systems can be found in [BCCL91] Work on graph based approaches to database querying appears in [CMW87, CMW88,GPG90, GG93] A proposal for a language for querying user defined visualizations of data can be found in [Cru93] The two sections in this chapter describe the architecture of the Hy system and provide a brief retrospective on its evolution. Within the architecture section we discuss a ....

I.F. Cruz, A.O. Mendelzon, and P.T. Wood. A graphical query language supporting recursion. In Proceedings of the ACM SIGMOD Conference on Management of Data, pages 323--330, 1987.

....so general that it is possible . to define a data model or type system together with an algebraic (or functional) query language. For example, it should be possible to define the relational model, nested relational models, complex object models, object oriented models, or graph models (e.g. [ScS91, CrMW87, GyPV90]) with corresponding algebraic query languages. to describe representations and query processing as another type system and algebra. For example, one should be able to model clustering representations for classes of objects, special kinds of index structures, graph like representations and so ....

Cruz, I.F., A.O. Mendelzon, and P.T. Wood, A Graphical Query Language Supporting Recursion. Proc. ACM SIGMOD 1987, 323-330.

....are more ambitious tools for visual data manipulation. In this paper, we describe the approach to visual display and manipulation of databases that we have been investigating at the University of Toronto for the past few years. We present an overview and retrospective of the G project [CMW87, CMW88, CM90b, CM90c] and the GraphLog query language by commenting a few screen shots showing different aspects of the work, and referring to the literature for the theory behind the prototype. We then point out some challenging research issues that show that we have just scratched the surface of what is sure to be a ....

Isabel F. Cruz, Alberto O. Mendelzon and Peter T. Wood. A graphical query language supporting recursion. In Proc. ACM-SIGMOD 1987 Annual Conference on Management of Data, pages 323--330, 1987.

....The query language could be improved by introducing greater conciseness. Examples include removing the necessity for the output of subqueries to be duplicated (although this duplication is performed by the interface) and allowing paths to be specified by means of regular expressions, as in G [CMW87] This would allow recursive queries to be formulated in QUIVER, although the translation could then no longer generate simply OQL. Another extension to QUIVER would be the introduction of negation, for which we are considering the use of crossed out arcs, as in GraphLog [CEH 94] for ....

I. F. Cruz, A. O. Mendelzon, and P. T. Wood. A graphical query language supporting recursion. In Proc. ACMSIGMOD Int. Conf. on Management of Data, pages 323--330, 1987.

....has been a great asset. However, the fact that queries which are especially useful in new application domains are not expressible in traditional query languages has led to proposals for more powerful query languages, such as the logic based language Datalog [23] and our query language G [9, 10]. The original proposal for the relational model included two query languages of equivalent expressive power: the relational calculus and the relational algebra [7] These languages have been used as the yardstick bywhich other query languages are classified; a query language is said to be ....

I. CRUZ, A. MENDELZON, AND P. WOOD, A graphical query language supporting recursion, in Proceedings of the ACM SIGMOD Conference on Management of Data, San Francisco, Calif., May 27--29, 1987, ACM, New York, pp. 323--330.

....Kornatzky [BK90] propose a logic whose formulas specify patterns over the hypertext graph. Graph query languages: Work in using graphs to model databases, motivated by applications such as software engineering and computer network management, led to the G, G and GraphLog graph based languages [CMW87, CMW88, CM90] In particular, G and G are based on labeled graphs; they support regular path expressions and graph construction in queries. GraphLog, whose semantics is based on Datalog, was applied to Hypertext queries in [CM89] Paredaens et al. [PdBA 92] developed a graph query language ....

Isabel F. Cruz, Alberto O. Mendelzon, and Peter T. Wood. A graphical query language supporting recursion. In Proc. of ACM SIGMOD Conf. on Management of Data, pages 323--330, San Francisco, CA, 1987.

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I.F. Cruz, A.O. Mendelzon, P.T. Wood, "A Graphical Query Language Supporting Recursion", SIGMOD Record Vol 16, Issue 3, 1987.

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I. Cruz, A. Mendelzon, and P. Wood. A graphical query language supporting recursion. In Proc. 1982.

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I.S. Cruz, A.O. Mendelzon, and P.T. Wood. A graphical query language supporting recursion. In Proc. 1982 International Conference on Management of Data, pages 323--330, Orlando (Florida, USA), June 1982.

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I.F. Cruz, A.O. Mendelzon, and P.T. Wood, A Graphical Query Language Supporting Recursion. Proc. ACM SIGMOD, 1987, 323-330.

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I. F. Cruz, A. O. Mendelzon and P. T. Wood, `A graphical query language supporting recursion', Proc. ACM SIGMOD Conf. on Management of Data, 1987, pp. 323--333.

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Isabel F. Cruz, Alberto O. Mendelzon, and Peter T. Wood. A Graphical Query Language Supporting Recursion. In SIGMOD-Record 1987, ACM, pages 323-330.

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