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About 501 papers for “XPath queries”

XSQ: Streaming XPath Queries

Peng Feng, Sudarshan S. Chawathe · Digital Repository at the University of Maryland (University of Maryland College Park) · 2002

We describe the design and implementation of XSQ, a system for evaluating XPath 1.0 queries on streaming XML data. Each XML element in the input data is presented to the system only once in a serial order determined by the data source. It is not possible to seek forward or backward in the data stream, and data cannot be recalled unless explicitly buffered by the system. Processing XPath queries correctly and efficiently in this environment is a challenging task and, to the best of our knowledge, XSQ is the first system that efficiently implements XPath queries with features such as closures and multiple predicates. XSQ is efficient in both time and space. Stream query processing typically adds only 25% to the time required for parsing the stream (and discarding results). XSQ's space usage is optimal in the sense that it buffers only data that must be buffered by all streaming query processors. We describe the formal framework of hierarchical pushdown transducers that forms the basis of the XSQ system and highlight experimental results on real and synthetic data. (Also UMIACS-TR-2002-81)

Cited by 3Open access

FILTERING UNSATISFIABLE XPATH QUERIES

2012

Abstract. The satisfiability test checks, whether or not the evaluation of a query returns the empty set for any input document, and can be used in query optimization for avoiding the submission and the computation of unsatisfiable queries. Thus, applying the satisfiability test before executing a query can save processing time and query costs. We focus on the satisfiability problem for queries formulated in the XML query language XPath, and propose a schema-based approach to the satisfiability test of XPath queries, which checks whether or not an XPath query conforms to the constraints in a given schema. If an XPath query does not conform to the constraints given in the schema, the evaluation of the query will return an empty result for any valid XML document. Thus, the XPath query is unsatisfiable. We present a complexity analysis of our approach, which proves that our approach is efficient for typical cases. We present an experimental analysis of our developed prototype, which shows the optimization potential of avoiding the evaluation of unsatisfiable queries. 1

Cited by 0

DISCOVERING VEILED UNSATISFIABLE XPATH QUERIES

Volker Linnemann · 2012

The satisfiability problem of queries is an important determinant in query optimization. The application of a satisfiability test can avoid the submission and the unnecessary evaluation of unsatisfiable queries, and thus save processing time and query costs. If an XPath query does not conform to constraints in a given schema, or constraints from the query itself are inconsistent with each other, the evaluation of the query will return an empty result for any valid XML document, and thus the query is unsatisfiable. Therefore, we propose a schema-based approach to filtering the XPath queries not conforming to the constraints in the schema and the XPath queries with conflicting constraints. We present a complexity analysis of our approach, which proves that our approach is efficient at typical cases. We present an experimental analysis of our prototype, which shows the optimization potential of avoiding the evaluation of unsatisfiable queries. 1

Cited by 0

XPath queries on streaming data

Feng Peng, Sudarshan S. Chawathe · 2003

We present the design and implementation of the XSQ system for querying streaming XML data using XPath 1.0. Using a clean design based on a hierarchical arrangement of pushdown transducers augmented with buffers, XSQ supports features such as multiple predicates, closures, and aggregation. XSQ not only provides high throughput, but is also memory efficient: It buffers only data that must be buffered by any streaming XPath processor. We also present an empirical study of the performance characteristics of XPath features, as embodied by XSQ and several other systems.

Cited by 9

XPath Queries on Streaming Data

Feng Peng, et al. · 2003

We present the design and implementation of the XSQ system for querying streaming XML data using XPath 1.0. Using a clean design based on a hierarchical arrangement of pushdown transduc-ers augmented with buffers, XSQ supports features such as multiple predicates, closures, and aggregation. XSQ not only provides high throughput, but is also memory efficient: It buffers only data that must be buffered by any streaming XPath processor. We also present an empirical study of the performance characteristics of XPath features, as embodied by XSQ and several other systems.

Cited by 0

Thresholded debugging of XPath queries

Jesús M. Almendros-Jiménez, Alejandro Luna, Ginés Moreno · 2015

We have recently designed/implemented a method for debugging XPath queries which produces a set of alternative XPath expressions with higher chances for retrieving answers from XML files. In this paper we focus on the scalability of our debugger for dealing with massive XML documents by making use of the new command FILTER which is intended to prematurely disregard those computations leading to non significant solutions (i.e., with a poor “chance degree” according to the user's preferences). The key point is the natural capability for performing “dynamic thresholding” enjoyed by the fuzzy logic language used for implementing the tool, which somehow connects with the so-called ≪top-k answering problem≫ very well-known in the fuzzy logic and soft computing arenas.

Cited by 3

XPath queries on streaming data

Feng Peng, Sudarshan S. Chawathe · 2003

We present the design and implementation of the XSQ system for querying streaming XML data using XPath 1.0. Using a clean design based on a hierarchical arrangement of pushdown transducers augmented with buffers, XSQ supports features such as multiple predicates, closures, and aggregation. XSQ not only provides high throughput, but is also memory efficient: It buffers only data that must be buffered by any streaming XPath processor. We also present an empirical study of the performance characteristics of XPath features, as embodied by XSQ and several other systems.

Cited by 198

XPlainer: Visual Explanations of XPath Queries

Mariano P. Consens, John W. S. Liu, Flavio Rizzolo · 2007

The popularity of XML has motivated the development of novel XML processing tools many of which embed the XPath language for XML querying, transformation, constraint specification, etc. XPath developers (as well as less technical users) have access to commercial tools to help them use the language effectively. Example tools include debuggers that return the result of XPath subexpressions visualized in the context of the input XML document. This paper introduces XPlainer, a language that provides explanations of why XPath expressions return a specific answer. An explanation returns precisely the nodes in the input XML document that contribute to the answer. We provide a complete formalization for explanation queries based on the semantics of XPath. This enables the use of XPath engines for the evaluation of explanation queries. We describe a tool that uses XPlainer queries to provide visual explanations. The XPlainer-Eclipse tool is built on an extensible development environment that includes editors for visualizing both XML documents and XPath expressions as trees together with the explanation of the answers.

Cited by 10

Containment between unions of xpath queries

Zhou, Rui, Liu, Chengfei, Wang, Junhu et al. · Figshare · 2024

In this paper, we address the containment problem for unions of XPath queries with and without schema. We find the problem can be always reduced into containment problem between one single query and a union of queries. When schema is not available, the problem can be further reduced into checking containment between pairwise queries(each from one union), but this only holds for some XPath subsets, such as XP{/,//,[]}, but not for XP{/,//,[],∗}. We then show the problem is still solvable in XP{/,//,[],∗}, though no efficient algorithm exists. When schema is at hand, we propose a strategy to rewrite a query into a union of simplified queries based on schema information, and then apply methods developed when schema is not taken into account. The problem is then reduced into checking containment between unions of queries in XP{/,[]}without schema.

Cited by 0Open access

Efficient Algorithms for Processing XPath Queries

Georg Gottlob, Christoph Koch, Reinhard Pichler · Elsevier eBooks · 2002

Our experimental analysis of several popular XPath processors reveals a striking fact: Query evaluation in each of the systems requires time exponential in the size of queries in the worst case. We show that XPath can be processed much more efficiently, and propose main-memory algorithms for this problem with polynomial-time combined query evaluation complexity. Moreover, we show how the main ideas of our algorithm can be profitably integrated into existing XPath processors. Finally, we present two fragments of XPath for which linear-time query processing algorithms exist and another fragment with linear-space/quadratic-time query processing.

Cited by 238Open access

Testing XPath queries using model checking

Riva Álvarez, Claudio A. de la, Tuya González, Pablo Javier, García Fanjul, José · Consultation of the Doctoral Thesis Database (TESEO) (Ministerio de Educación, Cultura y Deporte) · 2006

Cited by 0Open access

ABSTRACT Processing Content-Oriented XPath Queries

Börkur Sigurbjörnsson, Jaap Kamps · 2008

Document-centric XML collections contain text-rich documents, marked up with XML tags that add lightweight semantics to the text. Querying such collections calls for a hybrid query language: the text-rich nature of the documents suggests a content-oriented (IR) approach, while the mark-up allows users to add structural constraints to their IR queries. Hybrid queries tend to be more expressive, which should lead—in principle—to better retrieval performance. In practice, the processing of these hybrid queries within an IR systems turns out to be far from trivial, because a delicate balance between structural and content information needs to be sought. We propose an approach to processing such hybrid content-and-structure queries that decomposes a query into multiple content-only queries whose results are then combined in ways determined by the structural constraints of the original query. We evaluate our methods using the INEX 2003 test-suite, and show (1) that effective ways of processing of content-oriented XPath queries are non-trivial, (2) that there are differences in the effectiveness for different topics types, but (3) that with appropriate processing methods retrieval effectiveness can improve.

Cited by 0

Validity of Positive XPath Queries with . . .

Kenji Hashimoto, Yasunori Ishihara, et al. · 2011

This paper discusses the validity problem for positive XPath queries with wildcard in the presence of DTDs. A given XPath query p is valid under a DTD D if, for every XML document T conforming to D, the answer to p on T is nonempty. The validity problem is one of the basic static analyses of queries, together with the satisfiability and the containment problems. Although the validity problem is the dual of the satisfiability problem, the complexity of validity for positive XPath classes is not obvious because the XPath class does not contain the negation operator. In this paper, first, it is shown that the path union operator in XPath queries easily makes the validity problem intractable. Then, we focus on wildcard, which is a special case of path union and more popular than path union in the real world. Interestingly, wildcard together with child and descendant-orself axes and qualifier causes intractability while the validity problem becomes tractable for XPath classes defined by any combination of three of child axis, descendant-or-self axis, qualifier, and wildcard.

Cited by 0

Extending XPath to Support Linguistic Queries

Steven Bird, Yi Chen, Susan B. Davidson et al. · ScholarlyCommons (University of Pennsylvania) · 2005

Linguistic research and language technology development employ large repositories of ordered trees. XML, a standard ordered tree model, and XPath, its associated language, are natural choices for storing and querying linguistic data. However, several important expressive features required for linguistic queries are missing in XPath. In this paper, we motivate and illustrate these features with a variety of linguistic queries. Then we define extensions to XPath which support linguistic tree queries. We provide a relational representation for trees, and define an SQL translation for queries. Experiments demonstrate that the query system is significantly faster than other linguistic tree query systems for a wide range of queries. 1

Cited by 31Open access