Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/950
Title: Expressiveness of XSDs: from practice to theory, there and back again
Authors: BEX, Geert Jan 
MARTENS, Wim 
NEVEN, Frank 
Schwentick, Thomas
Issue Date: 2005
Publisher: ACM
Source: Proceedings of the 14th international conference on World Wide Web. p. 712-721.
Abstract: On an abstract level, XML Schema increases the limited expressive power of Document Type Definitions (DTDs) by extending them with a recursive typing mechanism. However, an investigation of the XML Schema Definitions (XSDs) occurring in practice reveals that the vast majority of them are structurally equivalent to DTDs. This might be due to the complexity of the XML Schema specification and the difficulty to understand the effect of constraints on typing and validation of schemas. To shed some light on the actual expressive power of XSDs this paper studies the impact of the Element Declarations Consistent (EDC) and the Unique Particle Attribution (UPA) rule. An equivalent formalism based on contextual patterns rather than on recursive types is proposed which might serve as a light-weight front end for XML Schema. Finally, the effect of EDC and UPA on the way XML documents can be typed is discussed. It is argued that a cleaner, more robust, stronger but equally efficient class is obtained by replacing EDC and UPA with the notion of 1-pass preorder typing: schemas that allow to determine the type of an element of a streaming document when its opening tag is met. This notion can be defined in terms of restrained competition regular expressions and there is again an equivalent syntactical formalism based on contextual patterns.
Document URI: http://hdl.handle.net/1942/950
Link to publication: http://doi.acm.org/10.1145/1060745.1060848
ISBN: 1-59593-046-9
Category: C1
Type: Proceedings Paper
Appears in Collections:Research publications

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