V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl, "From structured documents to novel query facilities," in SIGMOD, 1994.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....to pinpoint. Documents are often only weakly structured using HTML tags, and the inner logical organization is user dependent. Thus, automatic extraction of, say, article titles, becomes a difficult task. Every developer of Web applications has to deal with, at least, some of the above issues [1, 2, 4, 5, 6, 7, 8, 9, 11, 18, 19]. A problem in many of the efforts undertaken in the past is that they adopt a complete system approach. Thus their solutions are often tailored to a specific application, rather than being general. Additionally, by being parts of complete systems, solutions cannot be used independently, or ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proc. SIGMOD, 1994.

....as a universal data repository, offering access to sources whose data organization varies from strictly structured databases to almost completely unstructured pages, and everything in between. Consequently, much research has recently focused on data integration and data translation systems [10, 6, 9, 8, 17, 13, 2, 19], whose goals are to allow applications to utilize data from many sources, with possibly widely varying formats. These research efforts have established a common data model of semistructured data, for uniformly representing data from any source. Recently, however, it is being realized that having ....

....ancestors, have a body and a head [18, 12, 11] In the body, node variables are introduced, operated upon by predicates, and related by edges and paths. We consider here the component that seems to be the more difficult to treat, for deriving schema information, namely generalized path expressions [10, 18, 3, 6, 12], of the form x 0 P 1 x 1 P 2 x 2 : Pn xn where the x i s are variable names, and the P i s are regular expressions or path variables. Intuitively, given a data graph G, such expressions search for nodes v 0 ; v n s.t. the path between v i Gamma1 and v i ,i = 1 : n, matches P i , ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proc. ACM SIGMOD Symp. on the Management of Data, 94, pages 313--324, 1994.

....syntax and offers a query language based on SDQL [27] the language partially derived from DSSSLQuery and HyQ. This new language will run on top of OQL, the database query language. Some research work has already be done in the field of defining an SGML HyTime query language on top of OQL [29,13]. We have obtained a very good foundation for an SGML HyTime repository. Concerning HyTime, we are convinced that the HyTime concepts fulfil our hypermedia needs, but we are still waiting for the HyTime tools to come to the market. Last but not least, we must improve performance because we will ....

V. Christophides, S.Abitetoul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. 13th ACM SIGMOD Conference, 1994.

....relationships whereas XML Schema additionally provides generalization specialization relationships. Various query languages for semistructured data have been developed in order to deal with the complex and nested structure of these data. Many languages use path queries [KKS92, dBV93, CACS94, AQM 97, KS01] which have emerged as an important class of browsing style queries on the Web. For XML data, in particular, XPath [XPa99] like expressions are used. Our work focuses besides path queries on the possibility to ask for all elements of a certain type or for elements with similar ....

....[MW95, AV97] allowing users to query data without complete knowledge about the structure. These approaches focus on aggregation relationships whereas our approach exploits generalization relationships between concepts. Also, there have been work in the context of object oriented databases [dBV93, CACS94] These approaches allow abbreviated or generalized path expressions. dBV93] considers schema based completion of path expressions, but does not deal with typing constraints of multiple path expressions. KS01] uses the notion of flexible queries; a flexible query is a query graph; an edge in ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proc. ACM Symposium on Principles of Database Systems, 1994.

....approach is that the top level IMS can leverage the facilities of the underlying IMS (e.g. concurrency control, recovery, caching, index structures, etc. without significant Figure 1: Common integration architectures Layering [8] 15] 41] 46] 9] 47] 20] 38] 39] 57] 19] 42] 23] 56] 60][12] [29] 54] 27] Loose Coupling (or) Middleware Integration [40] 62] 25] 26] 16] 4] 45] 13] Extension [44] 31] 33] 18] 17] 35] 20] 22] 58] 51] 21] 65] 53] 61] 37] 35] 32] 30] 24] 5] 36] 28] 14] 55] 43] 11] Text Retrieval Relational OO Text Retrieval Semistructured ....

....for translating queries over XML documents into SQL or OQL queries over the underlying database, and (iii) a mechanism for translating the result of database query executiong into XML. There are several proposals for implementing XML repositories on top of relational [23, 29, 54, 56] and object [60, 12, 27] database systems, differing in their choices for (i) ii) and (iii) There are three basic alternatives for mapping XML documents into relational tables. The simplest, and least useful mapping, is to store an entire XML document as a single database attribute. Another possibility is to ....

[Article contains additional citation context not shown here]

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proceedings of the ACM SIGMOD Intl. Conf. on Management of Data, pages 313--324, May 1994.

.... the trend for schema conversion has always been between consecutive models or models with overlapping time frames, as they have evolved (e.g. between Network and Relational models [8, 9] between ER and OO models [10, 11] or between UML and XML models [12, 13, 14, 15] For instance, [16] deals with conversion problems in OODB area; since OODB is a richer environment than RDB, their work is not readily applicable to our application. The logical database design methods and their associated conversion techniques to other data models have been extensively studied in ER research. For ....

Christophides, V., Abiteboul, S., Cluet, S., Scholl, M.: "From Structured Document to Novel Query Facilities". In: ACM SIGMOD International Conference on Management of Data, Minneapolis, MN (1994)

....system. Note that the entries in this table represent only the most common cases. Individual systems might use some variations or extensions of these models and languages. Figure 1: Common integration architectures Layering [6] 16] 41] 46] 7] 21] 38] 39] 52] 20] 42] 24] 51] 54][13] [30] 49] 28] Loose Coupling [40] 56] 9] 11] 12] 26] 27] 17] 3] 45] 14] Extension [44] 32] 34] 19] 18] 35] 21] 23] 53] 47] 22] 57] 48] 55] 37] 35] 33] 31] 25] 4] 36] 29] 15] 50] 43] 10] Relational OO Text Retrieval Semistructured Relational OO Table 2: Classification of ....

....for translating queries over XML documents into SQL or OQL queries over the underlying database, and (iii) a mechanism for translating the result of database query execution into XML. There are several proposals for implementing XML repositories on top of relational [24, 30, 49, 51] and object [54, 13, 28] database systems, differing in their choices for (i) ii) and (iii) There are three basic alternatives for mapping XML documents into relational tables. The simplest, and least useful mapping, is to store an entire XML document as a single database attribute. Another possibility is to ....

[Article contains additional citation context not shown here]

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proc. of ACM SIGMOD Intl. Conf. on Management of Data, pages 313--324, May 1994.

....an increasing interest in the research community for the design of high level, declarative languages for querying it. WebSQL [MMM97] integrates textual retrieval with structure and topologybased queries. Instead of trying to model document structure with some kind of object oriented schema, as in [CACS94, QRS 95] a minimalist relational approach is taken: each Web document is associated with a tuple in a virtual Document relation and each hypertext link with a tuple in a virtual Anchor relation. In order to query these virtual tables, one must first define computable sub domains, either using ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proc. ACM SIGMOD'9J, pages 313-324, 1994.

....transformation from XML DTD to relational schema which requires human experts to write an XML based transformation rule. Some work has been done in [17] dealing with the transformation from re lational tables to XML documents. There has been some transformation work in the OODB area as well [6]. Since OODB is a richer environment than RDB, their work is not readily applicable to our application. The logical database design methods and their associated transformation techniques to other data models have been extensively studied in ER research. For instance, 3] presents an overview of ....

Christophides, V., Abiteboul, S., Cluet, S., Scholl, M. "From Structured Document to Novel Query Facilities", Proc. ACM $IGMOD, Minneapolis, Minnesota, 1994.

....DTD and XML document in Tables 6.1 and 6.2. 98 mon CDATA #REQUIRED day CDATA #IMPLIED ln CDATA #REQUIRED format (ACM IEEE) #IMPLIED Table 6.1: Example of a DTD for Conference. 6. 2 Related Work Conversion between di#erent models has been extensively investigated [ZCF97] For instance, [CAC94] deals with transformation problems in the OODB area; since OODB is a richer environment than RDB, their work is not readily applicable to our application. The logical database design methods and their associated transformation techniques to other data models have been extensively studied in ER ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. "From Structured Document to Novel Query Facilities". In ACM SIGMOD, Minneapolis, MN, Jun. 1994.

....designed structures and indices [8, 10] and particular query optimization techniques [9, 7] Examples are Strudel, Lore [1] OODBMS In this approach, the rich data modeling capabilities of objectoriented database systems are exploited. Processing of SGML documents using OODBMS was discussed in [3]. The conclusion was that this is feasible with some extensions to OO query languages. RDBMS In this approach semistructured data are mapped into tables of a relational scheme and queries in a semistructured query language are translated into SQL queries [14, 4] It is still unclear which way ....

....semi structured techniques is that this This work was supported in part by RFBR (grant 98 01 00436) and INTAS (grant OPEN 97 11109) approach turns it back on 20 years work invested in relational and object oriented database technology. Therefore, usage of relational [14, 6] object oriented [3, 13] and object relational [15] databases for storage of semistructured data recently attracted attention. In this work we focus on relational model. A number of methods to store semistructured data in relations were discussed [4, 6, 14] The crucial decision here is to select relational scheme to ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proc. of the SIGMOD'94, 1994.

....partly based on DTDs, too; hence they do not support abstraction concepts like generalization. These query languages make extensive use of path expressions, to navigate through nested structures. We propose a query language that may contain schema expressions. Like in object oriented languages [CACS94, Cat96] too, our query language support modeling constructs like aggregation and generalization. Queries can be written against this schema, refer to schema concepts, e.g. the type of an element and then are translated automatically into one or more classical path expressions, no longer ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In SIGMOD, 1994.

....keyword search etc) Thus, the search possibilities are circumscribed by the limited choices provided by the search interface, as opposed to the possibilities opened up by ad hoc querying. Database researchers have also investigated issues related to querying information present in documents ([17, 1, 4, 2]) Their approach to the problem is to pro vide a database view of the structured information present in documents. Most works in this direction follow the idea of mapping the underlying grammar of the document to an appropriate database scheme. Thus, when the document is parsed using this ....

.... richer models such as the object oriented model) and query processing (e.g. relational query optimization techniques) together with the need created by developments such as the Web has stimulated fresh investigation of issues related to querying and updating structured data stored in doc uments ([1, 4, 2]) In [1] Abiteboul, Cluet, and Milo make use of the grammar of a document to map it to an appropriate object oriented database. They introduce the notion of a structuring schema which consists of the database schema and the grammar annotated with database programs that specify how terminals and ....

[Article contains additional citation context not shown here]

V. Christophides, S. Cluet, S. Abiteboul, and M. Scholl "From structured documents to novel query facilities." In A CM SIGMOD International Conference on Mana9ement of Data, 1994.

....to their tag name. SGML attributes are represented by an attribute node under the element node. In the example in figure 2, expressions like body.table[#FIRST] and i. name are path expressions; they perform selections on the results in an OQL like manner (our syntax is inspired by POQL [11]) A path expression can be seen as the traversal of a tree: an expression .L (dot selection) finds the children with label L one level down the tree, an expression . L (dot dot selection) finds the children with label L at any level down the tree. It must be noted here that objects can form ....

....limit recursive link traversal to target documents on the same server or domain. It will be possible though to follow an explicit finite number of global links. 6. Related work Other works have looked at querying structured or semi structured information, either from a database point of view [4, 11]; from a document processing point of view, as with HyQ [2] or SgmlQL [16] or for hypertexts [9, 8, 19] Our selection of objects is similar to the generalized path expressions found in POQL [11] or Gram [8] however, their interpretation is much simplified since our paths are concrete paths ....

[Article contains additional citation context not shown here]

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proceedings of the ACM SIGMOD Conference on Management of Data, Minneapolis, Minnesota, pages 313--324, 1994.

....only organized in a strict tree hierarchy. 1.2 Structured approach A possible way of storing an XML document in an OO database is to map the DTD into a database schema and to store the content as value of the data. We consider here the ODMG model [Cat94, RC97] This is the approached followed by [CACS94] and strongly supported by [MMA98] A difficulty here is the absence in the ODMG model of union in the type system which does not make the mapping quite natural. The advantages of using this model are the following: i)a rich type system useful for XML Data ii) closely control updating: parts of ....

....XML documents, but returning a valid document is an harder problem especially when it involves many DTDs. Query 1 and query 2 has shown the need for more flexible syntax, allowing incomplete paths and link operators. It could be based on previous research works such as: ffl the work on POQL [CACS94] that involves queries with complex paths and introduces path variables. ffl the work on WebSQL language [MMM96] or Rio [VP98] they allow for following simple links from a document without necessarely giving the paths to the linking elements. This is very important in XML where extended links ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In SIGMOD, pages 313--324, Minneapolis, Minnesota, May 1994.

....a variable called d (section 3.2 discusses assignments to variables) 3.1.1 Path expressions A crucial component of the language is the ability to select nodes or combinations of nodes in a tree. Our syntax for information selection in a tree is based on the idea of generalised path expressions [CACS94], which permit browsing a tree without a complete knowledge of its structure. A path expression consists of a series of path terms. Each path term begins either with the dot operator ( for accessing the direct children of a node, or the dot dot operator ( for accessing all the ....

....(although it must be noted that the examples here could be simplified with the use of macros [DD94,section 94.7] and unintuitive. Furthermore, HyQ doesn t provide any primitive for constructing information. Our selection of objects is similar to the generalised path expressions found in POQL [CACS94]; however, their interpretation is much simplified since our paths are concrete paths into untyped tree structures that are not constrained to a database schema. This need to query semi structured data without strict typing conventions has been recognised in Lorel [AQM96] which use coercion ....

Christophides, V., Abiteboul, S., Cluet, S., and Scholl, M., "From Structured Documents to Novel Query Facilities", in Proceedings of the ACM SIGMOD Conference on Management of Data, Minneapolis, Minnesota, pp313-324, 1994.

....projects and tools have emerged to map XML and similar semi structured data formats to traditional database systems. 17] studies storing and querying XML data using a relational database management system (RDBMS) Both [22] and [25] investigate semistructured data in relational databases, while [10, 28] studies SGML (the predecessor of XML) storage in an object oriented database management system (OODBMS) Oracle s XML SQL Utility (XSU) 27] and IBM s DB2 XML Extender [19] are well known commercial relational database products extended with XML support. They mainly provide two methods to manage ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proceedings of the ACM SIGMOD International Conference on Management of Data, Minneapolis, pages 313--324, June 1994.

....projects and tools have emerged to map XML and similar semi structured data formats to traditional database systems. 17] studies storing and querying XML data using a relational database management system (RDBMS) Both [22] and [25] investigate semistructured data in relational databases, while [10, 28] studies SGML (the predecessor of XML) storage in an object oriented database management system (OODBMS) Oracle s XML SQL Utility (XSU) 27] and IBM s DB2 XML Extender [19] are well known commercial relational database products extended with XML support. They mainly provide two methods to manage ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proceedings of the ACM SIGMOD International Conference on Management of Data, Minneapolis, pages 313--324, June 1994.

.... using special purpose query engines for semistructured data since an XML document can be regarded as an instance of a semistructured data set[3, 8, 10, 13, 15] The other is using traditional databases such as relational databases or object oriented databases for storing and querying XML documents[5, 7, 9, 16]. In particular, many approaches using RDBMSs have been proposed. That is, XML data is converted to relational tuples and XML queries are translated to SQL queries. However, to the best of our knowledge, there is no special work on the problem of using OODBMSs to store and query XML data. An ....

....many approaches using RDBMSs have been proposed. That is, XML data is converted to relational tuples and XML queries are translated to SQL queries. However, to the best of our knowledge, there is no special work on the problem of using OODBMSs to store and query XML data. An exception is work in [5] that processes SGML data using an OODBMS to store and query SGML documents 1 . This work was supported by the Brain Korea 21 Project. 1 Additionally, there is a special purpose XML query processor, Excelon[11] that is based on an OODBMS. In this paper, we propose a technique that stores ....

[Article contains additional citation context not shown here]

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proceedings of the ACM SIGMOD International Conference on the Management of Data, 1994.

....Internet. In order to facilitate the task of querying XML documents, efficient storage models for storing XML documents in database systems were studied. There are basically three alternatives: storing XML data in repositories designed for semistructured data [7, 9] in object oriented databases [1], and in relational systems [3, 4, 10, 11] A number of systems, such as Lore [7] XML GL and Tamino [9] also provide query interfaces for users. This paper will present, XParent, an XML document management system built on top of RDBMS. In comparison to other systems, XParent has its unique ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proceedings of the 20th ACM SIGMOD International Conference on Management of Data, 1994.

....work was supported by the Brain Korea 21 Project. SELECT x.company. address telephone) FROM person. parent x; The above is an example of an XML query, which is similar to Lorel[2] This query retrieves person s parents addresses or telephone numbers. It contains the regular path expressions[2, 6, 9], which are supported by general XML queries such as XML QL[10] and XQL. Some syntaxes, such as the star( in XML queries, enlarge the search space. In this example, almost all nodes under person must be visited because of person. Therefore, regular path indexes have been studied to solve this ....

....the queries. However, these query languages are not adequate for the semistructured data due to a lack of schema information. Even if schema information is provided, the structure can be changed by its own data. To solve this problem, regular path expressions are used for semi structured queries[2, 6, 9]. Indexes of semistructured data[16, 20, 22] are proposed to execute regular path expressions more rapidly. They combine the index structure and automata of the XML data. The target objects can be retrieved by traversing the appropriate automata graph for the regular path expression. Theoretical ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. SIGMOD, 1994.

....used for optimization in the query language UnQL. There is no real notion of schema in the context of XML yet, although there are many activities within this eld. Document Type De nitions are more in the avor of grammars. In Figure 3. 9 we present a DTD for articles that was rst presented in [CACS94] As an example a section can either consist of a title and at least one body (a gure or a paragraph) or of a title, an arbitrary number of bodies and at least one subsection. section ) bib ack) title, body ) subsectn ) Figure 3.9: A Document Type De nition for articles ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scoll. From structured documents to novel query facilities. In Proceedings of the ACM SIGMOD International Conference on Management of Data, pages 313-323, Minneapolis, MN, USA, May 1994.

....a scheme the type of a subclass speci es options that are forbidden by its superclasses. 1 Introduction The introduction of union types in object oriented schemes makes them more expressive. Usually, however, they are limited to disjoint unions [KV93] or labeled unions such as variant records [CACS94]. Because of this limitation the reasoning about these types remains simple [Car88, Rem89] We argue that general union types such as used in [LR89, AK89, CL94] are a useful extension and even arise naturally in data models without union types. We can use them, for instance, to model optional ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In ACM SIGMOD'94, pages 313-324, 1994.

....system as described in [BRRK94] does not support the automatic addition of new DTDs to the system. However, the authors claim their system can be easily extended to support other DTDs. The design of a newer version of HyOctane [RBP96] in fact, involves an openDTD approach. 6. 3 VERSO VERSO [CACS94], developed at INRIA in France, is an objectoriented database system for SGML documents. It is built on top of O 2 to exploit its sophisticated type system and extensible query language O 2 SQL. Using an extended version of the Euroclid SGML parser, VERSO maps DTDs into O 2 schema, and document ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. "From Structured Documents to Novel Query Facilities," In Proceedings of the ACM SIGMOD International Conference on Management of Data, pages 313-324, 1994.

....various of these approaches are either dedicated to a single media types like images [16, 5] or strongly application specific [22] or high level approaches [1] Nevertheless many ideas from this area influenced our approach. Another related area is the management of structured documents. In [3] for example a mapping from SGML documents into OODBs and an extension of an SQL like OODB query language is given in order to deal with SGML document retrieval. Another example is W3QS described in [14] W3QS is a query system for the World Wide Web and includes an SQLlike query language ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proc. of the ACM SIGMOD Intl. Conf. on Management of Data, pages 313--324, Minneapolis, Minn., 1994.

....XQuery [4] and Quilt [5] Unsurprisingly, it is not dicult to extend the OQL syntax with special constructs to handle XML data because these data have a treelike structure that can be naturally mapped to linked objects. In fact there are several proposals for such extensions, such as POQL [6], Ozone [14] Lorel [12] WebOQL [2] and X OQL [1] Instead of using one of the proposed languages, we developed our own, called XML OQL, because its syntax is better suited for our translations than other proposals. Unlike other proposals, XML OQL was designed to have clear semantics in the form ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proceedings of the 1994 ACM SIGMOD International Conference on Management of Data, Minneapolis, Minnesota, pages 313-324, May 1994.

....in Shanmugasundaram et al. 1999) 2) the input XML documents are all valid, and 3) the physical XML features such as entities or notations are not discussed but handled in the implementation. 2.1 Related Work Conversion between different models has been extensively investigated. For instance, Christophides et al. 1994) deals with transformation problems in the OODB area; since OODB is a richer environment than RDB, their work is 1 We differentiate two terms in this paper XML schema and XML Schema. The former refers to a general term for schema in the XML model, while the latter refers to one particular kind ....

Christophides, V., Abiteboul, S., Cluet, S., Scholl, M., Jun. 1994. "From Structured Document to Novel Query Facilities". In: ACM SIGMOD. Minneapolis, MN.

....of XML data very dicult. Consequently, we believe that the OODB technology has a better potential than the relational technology to become a good basis for storing and handling XML data. Even though there is already work on using OODBs for XML data, such as the work of Christophides, et al. [9] and the Lore project [21] there are still many open problems related to query processing and optimization. The most important criticism against the xed schema approach is that, in practice, the source of XML data is often not part of some database. Rather XML data are scattered throughout the ....

....for mapping XML types to ODL schemas and for translating XML queries into OQL queries. Our type system allows a mixture of typed and untyped XML data, where parts of the XML data may have a xed schema while others may be schema less. Our starting point is the work by Christophides, et al. [9] on storing and handling SGML data with OQL, but we go beyond that by supporting a type system well integrated with that of ODMG ODL that supports both semi structured and schema based XML data. Furthermore, our query language supports XML data construction in the form of XML tags, a feature now ....

[Article contains additional citation context not shown here]

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proceedings of the 1994 ACM SIGMOD International Conference on Management of Data, Minneapolis, Minnesota, pages 313-324, May 1994.

....structures (including nesting) and hence provides a much better basis for higher level database facilities than HTML. Together with its advanced linking facilities, it subsumes the power of many semi structured data representations. Work has already been done on query languages for SGML (e.g. [CACS94]) and this work could be adapted to XML (DSSSL also defines a form of query language called SDQL for accessing parts of SGML documents for use in formatting) The provision of query languages for XML, together with associated algebras and calculi, would provide an important base for the ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl, "From Structured Documents to Novel Query Facilities", Proc. SIGMOD '94, 313-324.

....the preferred one so far, is based on the use of self describing data, modeled as a labeled graph, without a prede ned schema. An example of the rst approach is the solution proposed to manage SGML documents in the O 2 object oriented database system with appropriate extensions of its data model [13]. An example of the second approach is the Stanford s Object Exchange Model (OEM) and a similar model has been also proposed at the University of Pennsylvania [8] In OEM each object has an arbitrary number of attributes, with di erent or equal names, whose values are other objects or atomic ....

....names can be modeled, and it does not support neither encapsulation nor object behavior. The approach with tagged union types requires few modi cations to a DBMS and preserves the advantages of traditional database languages with respect to the possibility of type checking and query optimization [13]. However the use of tagged union types, and their related case operators, is not exible enough to deal with semistructured data; for this reason, some researchers are currently investigating the possibility of switching to a more exible approach based on untagged union types. The approach ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In R. T. Snodgrass and M. Winslett, editors, Proceedings of the 1994 ACM SIGMOD International Conference on Management of Data, pages 313-324, Minneapolis, Minnesota, 24-27 May 1994. SIGMOD Record 23(2), June 1994.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proc. of ACM SIGMOD Conf. on Management of Data, pages 313--324, Minneapolis, Minnesota, May 1994.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proc. of ACM SIGMOD Conf. on Management of Data, pages 313--324, Minneapolis, Minnesota, May 1994.

....in description bases. 4 The RDF Query Language: RQL RQL is a typed query language relying on a functional approach (a la OQL [15 ] It is defined byaset of basic queries and iterators which can be used to build new ones through functional composition. RQL supports generalized path expressions, [18, 19, 3] featuring variables on labels for both nodes (i.e. classes) and edges (i.e. properties) As we will see in the sequel, the smooth combination of RQL schema and data path expressions is a key feature in order to satisfy the needs of several Semantic Web applications such as Web Portals and ....

....can be used in RQL filters for the traversal of RDF graphs at arbitrary depths. 4.2 Schema Queries In this subsection, we focus our attention on querying RDF schemas, regardless of any underlying instances. More precisely,we will see how RQL extends the notion of generalized path expressions [18, 19, 3] to entire class (or property) inheritance paths in order to implement schema browsing or filtering using appropriate conditions. Webelieve that declarative query support for navigating through taxonomies of classes and properties is quite useful for realscale Portal catalogs and E Marketplace ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proc. of ACM SIGMOD Conf. on Management of Data, pages 313--324, Minneapolis, Minnesota, May1994.

....data graph instantiation mechanism inspired by GRAM [6, 7] ffl We propose a declarative language, called RQL, to query semistructured RDF (meta)data and related schemas. RQL adopts the syntax and functional approach of OQL [12] while it features generalized path expressions in the style of POQL [15, 16, 2] or Lorel [4] The novelty of RQL lies in its ability to query complex semistructured data graphs using in a transparent way taxonomies of labels for nodes (i.e. classes) and edges (i.e. property types) as well as to query the schema vocabularies themselves. To the best of our knowledge RQL ....

....from X Artist where X.last name = Rodin This RQL query is just a shortcut of the following one: from X Artist, fYglast namefZg where X = Y and Z = Rodin 3. 3 Querying RDF (Meta)Data with Incomplete Schema knowledge In this subsection, we introduce RQL generalized path expressions [15, 16] featuring variables on both edge and node labels (i.e. property and class names) Consider for instance the following query: Q2: Find the target of properties (resources or values) whose name matches name . select Y from P Property, fXg PfYg where P like name To distinguish between ....

[Article contains additional citation context not shown here]

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proc. of ACM SIGMOD Conf. on Management of Data, pages 313--324, Minneapolis, Minnesota, May 1994.

....Tomake this kind of path expressions more compact for class equality (e.g. Z = Painter) shortcuts as fX:PaintergcreatesfYg arealso supported. The formal semantics of RQL mixed path expressions are given in Table 2. In other words, RQL extends the notion of generalized path expressions [15, 16, 3]toentire class (or property) inheritance paths. This is quite useful since resources can be multiply classified and several properties coming from different class hierarchies may be used for the same resource descriptions. Still RQL allows one to query properties emanating from resources only ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From Structured Documents to Novel Query Facilities. In Proc. of ACM SIGMOD Conf. on Management of Data, pages 313--324, Minneapolis, Minnesota, May1994.

....stored under different formats: relational or ODMG 1 model (in databases) SGML or LaTex (documents) DX formats (data exchange formats in scientific data) Step (CAD CAM data) etc. Their integration is a very active field of research and development (see for instance, for a very small sample, [13, 9, 10, 12, 11, 15, 25, 26]) In this paper, we provide a formal foundation to facilitate the integration of such heterogeneous data and the maintenance of heterogeneous replicated data. A sound solution for a data integration task requires a clean abstraction of the different formats in which data are stored, and means ....

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proc. ACM Sigmod, Minneapolis, 1994.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl, "From structured documents to novel query facilities," in SIGMOD, 1994.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, M. Scholl, "From structured Documents to Novel Query Facilities", in Proc. of SIGMOD 94, Minneapolis, US, 1994, pp. 313-324.

No context found.

Christophides, V., Abitebul, S., Cluet, S. and Scholl, M. "From Structured Documents to Novel Query Facilities". Proceedings of the ACM SIGMOD International Conference on Management of Data, Minnesota, USA. 1994.

No context found.

V. Christophides et al. From structured documents to novel query facilities. In Proceedings of the 1994 ACM SIGMOD Internation Conference on Management of Data, volume 23:2 of SIGMOD Record, pages 313--324. ACM Press, 1994.

No context found.

13 Christophides, V., Abiteboul, S., Cluet, S., Scholl, M.(' From Structured Documents to Novel Query Facilities. In Proceedings of ACM SIGMOD Conference on Management of Data, Minneapolis, Minnesota(nesota'

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In SIGMOD'94, pages 313--324. ACM, 1994.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, M. Scholl, From Structured Documents to Novel Query Facilities, Proc. of the ACM SIGMOD International Conference on Management of Data, 1994, pp. 313-324.

No context found.

13 Christophides, V., Abiteboul, S., Cluet, S., Scholl, M.(' From Structured Documents to Novel Query Facilities. In Proceedings of ACM SIGMOD Conference on Management of Data, Minneapolis, Minnesota(nesota'

No context found.

V. Christophides, et al., "From Structured Documents to Novel Query Facilities", SIGMOD Conf., 1994.

No context found.

Christophides, V., Abiteboul, S., Cluet, S., Scholl, M.: "From Structured Document to Novel Query Facilities". In: ACM SIGMOD, Minneapolis, MN (1994)

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In A CM SIGMOD International Conf. on Management of Data (SIGMOD '9), Minneapolis, pages 313-323, 1994.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proceedings of SIGMOD 94. ACM, 1994.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl, `From structured documents to novel query facilities', in Proceedings of the ACM International Conference on the Management of Data #SIGMOD# #Minneapolis, MN, 1994#.

No context found.

V. Christophides, S. Abiteboul, S. Cluet, and M. Scholl. From structured documents to novel query facilities. In Proceedings of the ACM SIGMOD Conference, Minneapolis, MN, May 1994. 24

First 50 documents  Next 50

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC