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54
Representing and querying XML with incomplete information
- ACM TODS
, 2006
"... We study the representation and querying of XML with incomplete information. We consider a simple model for XML data and their DTDs, a very simple query language, and a representation system for incomplete information in the spirit of the representations systems developed by Imielinski and Lipski [1 ..."
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Cited by 67 (9 self)
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We study the representation and querying of XML with incomplete information. We consider a simple model for XML data and their DTDs, a very simple query language, and a representation system for incomplete information in the spirit of the representations systems developed by Imielinski and Lipski [1984] for relational databases. In the scenario we consider, the incomplete information about an XML document is continuously enriched by successive queries to the document. We show that our representation system can represent partial information about the source document acquired by successive queries, and that it can be used to intelligently answer new queries. We also consider the impact on complexity of enriching our representation system or query language with additional features. The results suggest that our approach achieves a practically appealing balance between expressiveness and tractability.
Positive Active XML
- In Proc. of ACM PODS
, 2004
"... The increasing popularity of XML and Web services introduced a new generation of documents, called Active XML documents (AXML), where some of the data is given explicitly while other parts are given intensionally, by means of embedded calls to Web services. Web services in this context can exchange ..."
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Cited by 43 (17 self)
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The increasing popularity of XML and Web services introduced a new generation of documents, called Active XML documents (AXML), where some of the data is given explicitly while other parts are given intensionally, by means of embedded calls to Web services. Web services in this context can exchange intensional information, using AXML documents as parameters and results.
A framework for distributed XML data management. Extended version (Gemo technical report no
, 2005
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Distributed xquery
- In IIWeb
, 2004
"... XQuery is increasingly being used for ad-hoc integration of heterogeneous data sources that are logically mapped to XML. For example, scientists need to query multiple scientific databases, which are distributed over a large geographic area, and it is possible to use XQuery for that. However, the la ..."
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Cited by 30 (3 self)
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XQuery is increasingly being used for ad-hoc integration of heterogeneous data sources that are logically mapped to XML. For example, scientists need to query multiple scientific databases, which are distributed over a large geographic area, and it is possible to use XQuery for that. However, the language currently supports only the data shipping query evaluation model (through the document() function): it fetches all data sources to a single server, then runs the query there. This is a major limitation for many applications, especially when some data sources are very large, or when a data source is only a virtual XML view over some other logical data model. We propose here a simple extension to XQuery that allows query shipping to be expressed in the language, in addition to data shipping. Example 1.1 For a simple illustration, consider the following example:
XRPC: Interoperable and Efficient Distributed XQuery
- In VLDB
, 2007
"... We propose XRPC, a minimal XQuery extension that enables distributed yet efficient querying of heterogeneous XQuery data sources. XRPC enhances the existing concept of XQuery functions with the Remote Procedure Call (RPC) paradigm. By calling out of an XQueryfor-loop to multiple destinations, and by ..."
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Cited by 24 (5 self)
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We propose XRPC, a minimal XQuery extension that enables distributed yet efficient querying of heterogeneous XQuery data sources. XRPC enhances the existing concept of XQuery functions with the Remote Procedure Call (RPC) paradigm. By calling out of an XQueryfor-loop to multiple destinations, and by calling functions that themselves perform XRPC calls, complex P2P communication patterns can be achieved. The XRPC extension is orthogonal to all XQuery features, including the XQuery Update Facility (XQUF). We provide formal semantics for XRPC that encompasses execution of both read-only and update queries. XRPC is also a network SOAP sub-protocol, that integrates seamlessly with web services and Service Oriented Architectures (SOA), and AJAX-based GUIs. A crucial feature of the protocol is bulk RPC, that allows remote execution of many different calls to the same procedure, using possibly a single network round-trip. The efficiency potential of XRPC is demonstrated via an open-source implementation in MonetDB/XQuery. We show, however, that XRPC is not system-specific: every XQuery data source can service XRPC calls using a wrapper. Since XQuery is a pure functional language, we can leverage techniques developed for functional query decomposition to rewrite data shipping queries into XRPC-based function shipping queries. Powerful distributed database techniques (such as semi-join optimizations) directly map on bulk RPC, opening up interesting future work opportunities. 1.
Efficient maintenance techniques for views over active documents
- In International Conference on Extending Database Technology (EDBT
, 2009
"... Many Web applications are based on dynamic interactions between Web components exchanging flows of information. Such a situation arises for instance in mashup systems or when monitoring distributed autonomous systems. Our work is in this challenging context that has generated recently a lot of atten ..."
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Cited by 14 (4 self)
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Many Web applications are based on dynamic interactions between Web components exchanging flows of information. Such a situation arises for instance in mashup systems or when monitoring distributed autonomous systems. Our work is in this challenging context that has generated recently a lot of attention; see Web 2.0. We introduce the axlog formal model for capturing such interactions and show how this model can be supported efficiently. The central component is the axlog widget defined by one tree-pattern query or more, over an active document (in the Active XML style) that includes some input streams of updates. A widget generates a stream of updates for each query, the updates that are needed to maintain the view corresponding to the query. We exploit an array of known technologies: datalog optimization techniques such as Differential or MagicSet, constraint query languages, and efficient XML filtering (YFilter). The novel optimization technique we propose is based on fundamental new notions: a relevance (different than that of MagicSet), satisfiability and provenance for active documents. We briefly discuss an implementation of an axlog engine, an application that we used to test the approach, and results of experiments. 1.
An Approach to Optimize Data Processing in Business Processes
"... ipvs.uni-stuttgart.de In order to optimize their revenues and profits, an increasing number of businesses organize their business activities in terms of business processes. Typically, they automate important business tasks by orchestrating a number of applications and data stores. Obviously, the per ..."
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Cited by 11 (1 self)
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ipvs.uni-stuttgart.de In order to optimize their revenues and profits, an increasing number of businesses organize their business activities in terms of business processes. Typically, they automate important business tasks by orchestrating a number of applications and data stores. Obviously, the performance of a business process is directly dependent on the efficiency of data access, data processing, and data management. In this paper, we propose a framework for the optimization of data processing in business processes. We introduce a set of rewrite rules that transform a business process in such a way that an improved execution with respect to data management can be achieved without changing the semantics of the original process. These rewrite rules are based on a semi-procedural process graph model that externalizes data dependencies as well as control flow dependencies of a business process. Furthermore, we present a multi-stage control strategy for the optimization process. We illustrate the benefits and opportunities of our approach through a prototype implementation. Our experimental results demonstrate that independent of the underlying database system performance gains of orders of magnitude are achievable by reasoning about data and control in a unified framework. 1.
Satisfiability and relevance for queries over active documents
- In PODS
, 2009
"... Many Web applications are based on dynamic interactions between Web components exchanging flows of information. Such a situa-tion arises for instance in mashup systems [22] or when monitoring distributed autonomous systems [6]. This is a challenging prob-lem that has generated recently a lot of atte ..."
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Cited by 10 (4 self)
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Many Web applications are based on dynamic interactions between Web components exchanging flows of information. Such a situa-tion arises for instance in mashup systems [22] or when monitoring distributed autonomous systems [6]. This is a challenging prob-lem that has generated recently a lot of attention; see Web 2.0 [38]. For capturing interactions between Web components, we use ac-tive documents interacting with the rest of the world via streams of updates. Their input streams specify updates to the document (in the spirit of RSS feeds), whereas their output streams are defined by queries on the document. In most of the paper, the focus is on input streams where the updates are only insertions, although we do consider also deletions. We introduce and study two fundamental concepts in this setting, namely, satisfiability and relevance. Some fact is satisfiable for an active document and a query if it has a chance to be in the result of the query in some future state. Given an active document and a query, a call in the document is relevant if the data brought by this call has a chance to impact the answer to the query. We analyze the complexity of computing satisfiability in our core model (insertions only) and for extensions (e.g., with deletions). We also analyze the complexity of computing relevance in the core model.
The Data Ring: Community Content Sharing
- In Third Biennial Conference on Innovative Data Systems Research (CIDR 2007), Asilomar
, 2007
"... Information ubiquity has created a large crowd of users ..."
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Cited by 8 (5 self)
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Information ubiquity has created a large crowd of users
Regular rewriting of active XML and unambiguity
- In PODS
, 2005
"... We consider here the exchange of Active XML (AXML) data, i.e., XML documents where some of the data is given explicitly while other parts are given only intensionally as calls to Web services. Peers exchanging AXML data agree on a data exchange schema that species in particular which parts of the da ..."
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Cited by 7 (3 self)
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We consider here the exchange of Active XML (AXML) data, i.e., XML documents where some of the data is given explicitly while other parts are given only intensionally as calls to Web services. Peers exchanging AXML data agree on a data exchange schema that species in particular which parts of the data are allowed to be intensional. Before send-ing a document, a peer may need to rewrite it to match the agreed data exchange schema, by calling some of the services and materializing their data. Previous works showed that the rewriting problem is undecidable in the general case and of high complexity in some restricted cases. We argue here that this diculty is somewhat articial. Indeed, we study what we believe to be a more adequate, from a practical view point, rewriting problem that is (1) in the spirit of standard 1-unambiguity constraints imposed on XML schema and (2) can be solved by a single pass over the document with a computational device not stronger than a nite state au-tomaton. Following previous works, we focus on the core of the problem, i.e., on the problem on words. The results may be extended to (A)XML trees in a straightforward manner. 1.