Publishing Relational Data in XML: the SilkRoute Approach Mary Fernández AT&T Labs Atsuyuki M... more Publishing Relational Data in XML: the SilkRoute Approach Mary Fernández AT&T Labs Atsuyuki Morishima Shibaura Institute of Technology Dan Suciu University of Washington Wang-Chiew Tan University of Pennsylvania 1 Introduction For exchange on the Internet, relational ...
Query languages for data with irregular structure use regular path expressions for navigation. Th... more Query languages for data with irregular structure use regular path expressions for navigation. This feature is useful for querying data where parts of the structure is either unknown, unavailable to the user, or changes frequently. Naive execution of regular path expressions is inefficient however, because it ignores any structure in the data. We describe two optimization techniques for queries with regular path expressions. Both rely on graph schemas for specifying partial knowledge about the data's structure. Query pruning uses this structure to restrict navigation to only a fragment of the data; we give an efficient algorithm for rewriting any regular path expression query into a pruned one. Query rewriting using state extents can eliminate or reduce navigation altogether; it is reminiscent of optimizing relational queries using indices. There may be several ways to optimize a query using state extents; we give a polynomial space algorithm that finds all such optimizations. For restricted forms of regular path expressions, the algorithm is provably efficient. We also give an efficient approximation algorithm that works on all regular path expressions
Strudel is a system for implementing dataintensive Web sites, which typically integrate informati... more Strudel is a system for implementing dataintensive Web sites, which typically integrate information from multiple data sources and have complex structure. Strudel's key idea is separating the management of a Web site's data, the specification of its content and structure, and the visual representation of its pages. Strudel provides a declarative query language for specifying a site's content and structure, and a simple template language for specifying a site's HTML representation. This paper contains a comprehensive description of the Strudel system and details the benefits of declarative site specification. We describe our experiences using Strudel in a production application and describe three different, but complementary, systems that extend and improve upon Strudel's original ideas.
Managing Web sites is a tedious data-management task, because today's Web sites often are derived... more Managing Web sites is a tedious data-management task, because today's Web sites often are derived from multiple data sources and have complex structures. To simplify these tasks, Web-site builders need tools for managing Web sites' content and structure.
XML is a new standard that supports data exchange on the World-Wide Web. It is likely to become a... more XML is a new standard that supports data exchange on the World-Wide Web. It is likely to become as important and as widely used as HTML.
XML is the "lingua franca" for data exchange between inter-enterprise applications. In this work,... more XML is the "lingua franca" for data exchange between inter-enterprise applications. In this work, we describe SilkRoute, a framework for publishing relational data in XML. In SilkRoute, relational data is published in three steps. First, the relational tables are presented to the database administrator in a canonical XML view. Second, the database administrator defines in the XQuery query language a public, virtual XML view over the canonical XML view. Third, an application formulates an XQuery query over the public view. SilkRoute composes the application query with the public-view query, translates the result into SQL, executes this on the relational engine, and assembles the resulting tuple streams into an XML document.
Abstract. This paper presents structural recursion as the basis of the syntax and semantics of qu... more Abstract. This paper presents structural recursion as the basis of the syntax and semantics of query languages for semistructured data and XML. We describe a simple and powerful query language based on pattern matching and show that it can be expressed using structural recursion, which is introduced as a top-down, recursive function, similar to the way XSL is defined on XML trees. On cyclic data, structural recursion can be defined in two equivalent ways: as a recursive function which evaluates the data top-down and remembers all its calls to avoid infinite loops, or as a bulk evaluation which processes the entire data in parallel using only traditional relational algebra operators. The latter makes it possible for optimization techniques in relational queries to be applied to structural recursion. We show that the composition of two structural recursion queries can be expressed as a single such query, and this is used as the basis of an optimization method for mediator systems. Several other formal properties are established: structural recursion can be expressed in first-order logic extended with transitive closure; its data complexity is PTIME; and over relational data it is a conservative extension of the relational calculus. The underlying data model is based on value equality, formally defined with bisimulation. Structural recursion is shown to be invariant with respect to value equality.
Data-intensive Web sites have created a new form of knowledge base, as richly structured bodies o... more Data-intensive Web sites have created a new form of knowledge base, as richly structured bodies of data.
We address the problem of efficiently constructing materialized XML views of relational databases... more We address the problem of efficiently constructing materialized XML views of relational databases. In our setting, the XML view is specified by a query in the declarative query language of a middle-ware system, called SilkRoute. The middle-ware system evaluates a query by sending one or more SQL queries to the target relational database, integrating the resulting tuple streams, and adding the XML tags. We focus on how to best choose the SQL queries, without having control over the target RDBMS.
An important application of XML is the interchange of electronic data (EDI) between multiple data... more An important application of XML is the interchange of electronic data (EDI) between multiple data sources on the Web. As XML data proliferates on the Web, applications will need to integrate and aggregate data from multiple source and clean and transform data to facilitate exchange. Data extraction, conversion, transformation, and integration are all well-understood database problems, and their solutions rely on a query language. We present a query language for XML, called XML-QL, which we argue is suitable for performing the above tasks. XML-QL is a declarative, 'relational complete' query language and is simple enough that it can be optimized. XML-QL can extract data from existing XML documents and construct new XML documents.
Galax is a light-weight, portable, open-source implementation of XQuery 1.0. Started in December ... more Galax is a light-weight, portable, open-source implementation of XQuery 1.0. Started in December 2000 as a small prototype designed to test the XQuery static type system, Galax has now become a solid implementation, aiming at full conformance with the family of XQuery 1.0 specifications. Because of its completeness and open architecture, Galax also turns out to be a very convenient platform for researchers interested in experimenting with XQuery optimization.
We develop a new schema for unstructured data. Traditional schemas resemble the type systems of p... more We develop a new schema for unstructured data. Traditional schemas resemble the type systems of programming languages. For unstructured data, however, the underlying type may be much less constrained and hence an alternative way of expressing constraints on the data is needed. Here, we propose that both data and schema be represented as edge-labeled graphs. We develop notions of conformance between a graph database and a graph schema and show that there is a natural and efficiently computable ordering on graph schemas. We then examine certain subclasses of schemas and show that schemas are closed under query applications. Finally, we discuss how they may be used in query decomposition and optimization.
Publishing Relational Data in XML: the SilkRoute Approach Mary Fernández AT&T Labs Atsuyuki M... more Publishing Relational Data in XML: the SilkRoute Approach Mary Fernández AT&T Labs Atsuyuki Morishima Shibaura Institute of Technology Dan Suciu University of Washington Wang-Chiew Tan University of Pennsylvania 1 Introduction For exchange on the Internet, relational ...
Query languages for data with irregular structure use regular path expressions for navigation. Th... more Query languages for data with irregular structure use regular path expressions for navigation. This feature is useful for querying data where parts of the structure is either unknown, unavailable to the user, or changes frequently. Naive execution of regular path expressions is inefficient however, because it ignores any structure in the data. We describe two optimization techniques for queries with regular path expressions. Both rely on graph schemas for specifying partial knowledge about the data's structure. Query pruning uses this structure to restrict navigation to only a fragment of the data; we give an efficient algorithm for rewriting any regular path expression query into a pruned one. Query rewriting using state extents can eliminate or reduce navigation altogether; it is reminiscent of optimizing relational queries using indices. There may be several ways to optimize a query using state extents; we give a polynomial space algorithm that finds all such optimizations. For restricted forms of regular path expressions, the algorithm is provably efficient. We also give an efficient approximation algorithm that works on all regular path expressions
Strudel is a system for implementing dataintensive Web sites, which typically integrate informati... more Strudel is a system for implementing dataintensive Web sites, which typically integrate information from multiple data sources and have complex structure. Strudel's key idea is separating the management of a Web site's data, the specification of its content and structure, and the visual representation of its pages. Strudel provides a declarative query language for specifying a site's content and structure, and a simple template language for specifying a site's HTML representation. This paper contains a comprehensive description of the Strudel system and details the benefits of declarative site specification. We describe our experiences using Strudel in a production application and describe three different, but complementary, systems that extend and improve upon Strudel's original ideas.
Managing Web sites is a tedious data-management task, because today's Web sites often are derived... more Managing Web sites is a tedious data-management task, because today's Web sites often are derived from multiple data sources and have complex structures. To simplify these tasks, Web-site builders need tools for managing Web sites' content and structure.
XML is a new standard that supports data exchange on the World-Wide Web. It is likely to become a... more XML is a new standard that supports data exchange on the World-Wide Web. It is likely to become as important and as widely used as HTML.
XML is the "lingua franca" for data exchange between inter-enterprise applications. In this work,... more XML is the "lingua franca" for data exchange between inter-enterprise applications. In this work, we describe SilkRoute, a framework for publishing relational data in XML. In SilkRoute, relational data is published in three steps. First, the relational tables are presented to the database administrator in a canonical XML view. Second, the database administrator defines in the XQuery query language a public, virtual XML view over the canonical XML view. Third, an application formulates an XQuery query over the public view. SilkRoute composes the application query with the public-view query, translates the result into SQL, executes this on the relational engine, and assembles the resulting tuple streams into an XML document.
Abstract. This paper presents structural recursion as the basis of the syntax and semantics of qu... more Abstract. This paper presents structural recursion as the basis of the syntax and semantics of query languages for semistructured data and XML. We describe a simple and powerful query language based on pattern matching and show that it can be expressed using structural recursion, which is introduced as a top-down, recursive function, similar to the way XSL is defined on XML trees. On cyclic data, structural recursion can be defined in two equivalent ways: as a recursive function which evaluates the data top-down and remembers all its calls to avoid infinite loops, or as a bulk evaluation which processes the entire data in parallel using only traditional relational algebra operators. The latter makes it possible for optimization techniques in relational queries to be applied to structural recursion. We show that the composition of two structural recursion queries can be expressed as a single such query, and this is used as the basis of an optimization method for mediator systems. Several other formal properties are established: structural recursion can be expressed in first-order logic extended with transitive closure; its data complexity is PTIME; and over relational data it is a conservative extension of the relational calculus. The underlying data model is based on value equality, formally defined with bisimulation. Structural recursion is shown to be invariant with respect to value equality.
Data-intensive Web sites have created a new form of knowledge base, as richly structured bodies o... more Data-intensive Web sites have created a new form of knowledge base, as richly structured bodies of data.
We address the problem of efficiently constructing materialized XML views of relational databases... more We address the problem of efficiently constructing materialized XML views of relational databases. In our setting, the XML view is specified by a query in the declarative query language of a middle-ware system, called SilkRoute. The middle-ware system evaluates a query by sending one or more SQL queries to the target relational database, integrating the resulting tuple streams, and adding the XML tags. We focus on how to best choose the SQL queries, without having control over the target RDBMS.
An important application of XML is the interchange of electronic data (EDI) between multiple data... more An important application of XML is the interchange of electronic data (EDI) between multiple data sources on the Web. As XML data proliferates on the Web, applications will need to integrate and aggregate data from multiple source and clean and transform data to facilitate exchange. Data extraction, conversion, transformation, and integration are all well-understood database problems, and their solutions rely on a query language. We present a query language for XML, called XML-QL, which we argue is suitable for performing the above tasks. XML-QL is a declarative, 'relational complete' query language and is simple enough that it can be optimized. XML-QL can extract data from existing XML documents and construct new XML documents.
Galax is a light-weight, portable, open-source implementation of XQuery 1.0. Started in December ... more Galax is a light-weight, portable, open-source implementation of XQuery 1.0. Started in December 2000 as a small prototype designed to test the XQuery static type system, Galax has now become a solid implementation, aiming at full conformance with the family of XQuery 1.0 specifications. Because of its completeness and open architecture, Galax also turns out to be a very convenient platform for researchers interested in experimenting with XQuery optimization.
We develop a new schema for unstructured data. Traditional schemas resemble the type systems of p... more We develop a new schema for unstructured data. Traditional schemas resemble the type systems of programming languages. For unstructured data, however, the underlying type may be much less constrained and hence an alternative way of expressing constraints on the data is needed. Here, we propose that both data and schema be represented as edge-labeled graphs. We develop notions of conformance between a graph database and a graph schema and show that there is a natural and efficiently computable ordering on graph schemas. We then examine certain subclasses of schemas and show that schemas are closed under query applications. Finally, we discuss how they may be used in query decomposition and optimization.
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