Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Deductive and Object-Oriented Databases, pages 267--282. Springer Verlag (LNCS 760), 1993.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....allowing users to express concise (abbreviated) queries, so that they can manage with partial or even no knowledge of the database structure [37] Kifer, Kim and Sagiv [29] allow for similar abbreviated queries where a path expression can be bound to a sequence of attributes. Bussche and Vossen [48] use weights to help determine the meaning of certain abbreviated path expressions. Our use of succinct traversal specifications is intended to achieve such conciseness. Rumbaugh [42] proposed an operation propagation mechanism to specify object oriented software. The motivation of his work was ....

Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Deductive and Object-Oriented Databases, pages 267--282. Springer Verlag (LNCS 760), 1993.

....of a Person object, and Residence and City are attributes. They also allowed for abbreviated path expressions like X. Y.City[ newyork ] where Y is called a path variable and can be bound to any sequence of attributes. Bussche and Vossen allows abbreviated path expressions without wildcards [17]. To complete abbreviated path expressions into full ones, they added weights to the links in a database schema. The completion is aiming for the shortest connection between data objects. If several shortest paths exist, they take the union of them. Similar to propagation directives, such an ....

Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Stefano Ceri, Katsumi Tanaka, and Shalom Tsur, editors, Deductive and Object-Oriented Databases, pages 267--282, Phoenix, Arizona, 1993. Springer Verlag, Lecture Notes in CS, No. 760.

....allowing users to express concise (abbreviated) queries, so that they can manage with partial or even no knowledge of the database structure [26] Kifer, Kim and Sagiv [17] allow for similar abbreviated queries where a path expression can be bound to a sequence of attributes. Bussche and Vossen [8] use weights to help determine the meaning of certain abbreviated path expressions. Our use of succinct traversal specifications is intended to achieve such conciseness. Rumbaugh [30] proposed an operation propagation mechanism to specify object oriented software. The motivation of his work was ....

Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Proc. Deductive and Object-Oriented Databases, pages 267--282. Springer-Verlag (LNCS 760), 1993.

....the derivative functions accordingly. In the database community [1, 12, 2] more expressive path expressions have been considered, including l 1 ( nd an object o so that the current one is the value of instance variable o:l) and (l) nd the closest reachable object with instance variable l) [25]. These would also be interesting to investigate. Although adaptive programming has been conceived in the context of objectoriented programming, it is perfectly reasonable to also use this paradigm in the context of functional programming. The common sum of product types are 15 well suited for ....

Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Proc. of Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), volume 760 of Lecture Notes in Computer Science, pages 267-282, 1993. 17

....namely succinct subgraph specifications, to other domains than writing sequential programs. query languages The database community has made several efforts to introduce abbreviated queries or abbreviated path expressions. A representative, but far from complete, set of publications is: [19, 3, 15, 24, 17, 25, 8, 16, 13, 12, 23]. Simplifying queries has a long tradition in databases, and has previously been studied in the context of universal relation interfaces. The goal of those approaches is to have a schema shy way of writing queries. For a summary see: 5] Succinct subgraph specifications differ from earlier ....

Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Stefano Ceri, Katsumi Tanaka, and Shalom Tsur, editors, Deductive and ObjectOriented Databases, pages 267--282, Phoenix, Arizona, 1993. Springer Verlag, Lecture Notes in CS, No. 760.

....namely succinct subgraph specifications, to other domains than writing sequential programs. query languages The database community has made several efforts to introduce abbreviated queries or abbreviated path expressions. A representative, but far from complete, set of publications is: [Sci94, CS92, MU83, Ull83, NS88, VdBV93, IL94, MS93, Kim94, KKS92, SGL93]. The goal of those approaches is to have a schema shy way of writing queries. For a summary see: Har94] Succinct subgraph specifications differ from earlier approaches to abbreviated queries in the following major way: A succinct subgraph specification defines for a given schema both a set of ....

Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Stefano Ceri, Katsumi Tanaka, and Shalom Tsur, editors, Deductive and Object-Oriented Databases, pages 267--282, Phoenix, Arizona, 1993. Springer Verlag, Lecture Notes in CS, No. 760.

....WHERE Age(e) 50 returns the name and number of each employee being older than 50. Remark (attribute propagation against inheritance direction) Normally the attribute EmpNo : employee string is only applicable to employees. In order to simplify navigation in object oriented databases [BV93] attribute propagation in the opposite direction may be considered meaningful, too. SELECT (Name(p) EmpNo(p) FROM p:PERSON WHERE Age(p) 50 The query returns the name and employee number of each person being older than 50. Of course, when in a given database state a person does not play the ....

J. Van den Bussche and G. Vossen, An Extension of Path Expressions to Simplify Navigation in Object-Oriented Queries, Deductive and ObjectOriented Databases, Proc. DOOD'93 (S. Ceri, K. Tanaka, and S. Tsur, eds.), Springer, Berlin, LNCS 760, 1993.

....of that query over the relational schema. A universal relation interface requires no knowledge of database structure in terms of how information is distributed across relations. Similar approaches have been proposed for semantic data models [CS92] and object data models based on path expressions [dBV93] These various techniques for relational and other data models form the basis of our system. We adopt a minimal universal model and query language as the global model and language of the database network. The model is minimal in that it is devoid of structure; a query is expressed as a list of ....

....concept in the relational schema. In the case that node B is based on another data model, then a query interpretator for that model must be used. For example, as stated above, the idea of universal relation interfaces has been generalised to semantic data models [CS92] and object data models [dBV93] It is therefore a minimum requirement that each database system of the network is augmented with a universal translator module capable of translating local queries to universal queries and mapping universal queries to interpretations in terms of the local data model and schema. In the prototype ....

J. Van den Bussche and G. Vossen. An Extension of Path Expressions to Simplify Navigation in Object-Oriented Queries. In Proceedings 3rd Intl Conf on Deductive and Object-Oriented Databases, Arizona, USA, 1993.

....it easier for a user to ask a query. Particularly, we would like the user to be able to ask a query even if he she is not completely familiar with the schema. In this paper we have taken a few steps on this direction. We can further improve our approached by allowing incomplete path expressions [VdBV93, Gon94, IL94]. ....

J. Van den Bussche and G. Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Proc. Deductive and Object Oriented Databases, pages 267--283, 1993.

....Systems Center under ARPA Contract F33615 93 11339, and by the Air Force Rome Laboratories under ARPA Contract F30602 95 C 0119. y This author supported in part by the National Science Foundation under grant number IRI 9221268. beled edges as hypertext links. We focus on path queries [10, 17, 11, 2, 20, 4, 9, 19, 26], which have emerged as an important class of browsing style queries on graph data. Path queries are of the form find all objects reachable by paths whose labels form a word in r, where r is a regular expression over an alphabet of labels. In the context of the Web, we believe that queries ....

....local results to the client site, and assembling the final result at the client site. 19] considers the language WebSQL, which also incorporates path expressions, and provides a theory of query cost based on the notion of query locality. Path queries in object oriented databases are considered in [11]; they focus on the concise specification of path queries and the inference of completions of partially specified paths from schema information. To our knowledge, no previous work considers path constraints and their use in path query optimization. The paper is organized as follows. Section 2 ....

J. Van den Bussche and G. Vossen. An extension of path expressions to simplify navigation in objectoriented queries. In Proc. of Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), pages 267--282, 1993.

....WHERE X.vehicles[Y] color[Z] 1. 2) In this example, the selectors [Y] and [Z] are used to restrict an intermediate result (vehicles have to be automobiles) and to provide a result position for the query (the color is placed in Z) A more calculus oriented proposal for path expressions is given in [VV93]. Here the usage of class names in a path is allowed making possible the following query: f Z j employee.vehicles. automobile.color[Z]g (1.3) Even though the above approaches provide quite elegant techniques to access objects, we can observe certain limitations, as far as path expressions are ....

J. Van den Bussche and G. Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Proc. of the Intl. Conference on Deductive and Object-Oriented Databases (DOOD), pages 267 -- 282, 1993.

....and combine these in a formula, which is then used to arrange the paths in order of increasing semantic distance. They conclude with an empirical study measuring how many times the system selected those paths intended by the user who formulated an abbreviated query. Van den Bussche and Vossen [VdBV93] also seek to select paths from the set of possible paths specified by an abbreviated path, and they also assign weights to different kinds of links and select the path which minimizes a function, which they consider to be the conceptual distance between classes. If only one path minimizes the ....

....few most suitable paths out of a large set. Second, AQL gives a simple, definite answer to a query. It is equally suitable for use in ad hoc queries or in applications programming. In my view, methods which depend on systems of weighting or heuristics to determine what the user really meant [IL94, VdBV93, Sci94] are unsuitable for use in a database query language since it is too hard to predict what they will do with given inputs. Such approaches belong to the realm of very high level user interfaces, not to that of database query languages as defined in Section 2.1, any more than natural ....

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Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Stefano Ceri, Katsumi Tanaka, and Shalom Tsur, editors, Deductive and Object-Oriented Databases, pages 267-- 282, Phoenix, Arizona, 1993. Springer Verlag, Lecture Notes in CS, No. 760.

....of the form of internal representation. There has been little discussion of this mismatch. Many OO models ignore encapsulation and allow queries to be defined in terms of an objects attributes or methods (sometimes referred to collectively as properties ) In fact in some models (e.g. 10] [25]) attributes and methods without side effects are considered essentially the same. It has been shown that this is desirable in path expressions where attributes and methods can be used in the same place in the syntax (see section 4.1.1) This is in contradiction the policy of encapsulation. 3.3 ....

....ways of expressing this query) which could be evaluated in an OO query language using the simpler path expression Bought From.Name= MusicMaker . SELECT Date Acquired FROM Stock Item , Company WHERE Price 20 AND Bought From = Company Id AND Name= MusicMaker Figure 3: Example SQL query In [25] Bussche and Vossen present a detailed analysis of path expressions involving a model where paths can be expressed without all the attributes being stated explicitly. It is noted that when referring to attributes from an inherited class that the class name does not need to be referred to, i.e. an ....

Jan Van den Bussche and Gottfried Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Lecture Notes in Computer Science, volume 760. Springer-Verlag, 1993.

....and its use in optimizing the distributed evaluation of path queries. We use here an abstraction of the Web as a set of objects linked by labeled edges. An object represents a page (and possibly a site) and the labeled edges represent hypertext links. We focus on path queries [CM90, KKS92, dBV93, CACS94, MW95, AQM 96, BDHS96, MMM96, Suc96] which have emerged as an important class of browsing style queries on the Web. Path queries are of the form find all objects reachable by paths whose labels form a word in r, where r is a regular expression over an alphabet of labels. We present a ....

....is studied in [MW95] Specifically, the problem of finding all pairs of nodes connected by a simple path satisfying a given regular expression is shown to be NP complete in the size of the graph, and tractable subcases are identified. Path queries in object oriented databases are considered in [dBV93] they focus on the concise specification of path queries and the inference of completions of partially specified paths from schema information. Query languages for semi structured data, that include path expressions, are considered in [KS95, BDHS96, MMM96, Suc96] The language UnQL and its ....

J. Van den Bussche and G. Vossen. An extension of path expressions to simplify navigation in object-oriented queries. In Proc. of Intl. Conf. on Deductive and Object-Oriented Databases (DOOD), pages 267--282, 1993.

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