A visual language should be easy to use: a step forward for XML-GL
XML is spreading out as a standard for semistructured documents on the Web, so the possibility of querying XML documents which are linked by XML links is becoming a goal to achieve. In this paper we present XML-GL(rec), an extended version of the graphical query language for XML documents XML-GL. XML-GL allows to extract and restructure information from XML specified WWW documents. We extend XML-GL in the following directions: (i) XML-GL(rec) allows to represent XML simple links, so that it is possible to query whole XML specified WWW sites in a simple and intuitive way; (ii) XML-GL(rec) improves the expressive power of XML-GL, where only transitive closure can be expressed, by allowing generic recursion; (iii) finally, we permit the user to specify queries in an easier fashion, by allowing sequences of nested query, in the same way as in SQL. (C) 2002 Elsevier Science Ltd. All rights reserved.
xml query languages www recursion semantic web graphs