With the recent popularity of the World Wide Web, an enormous amount of heterogeneous information is now available online. As a result, information about real world objects may spread over different data sources and may be partial and inconsistent. How to manipulate such semistructured data is thus a challenge. Previous work on semistructured data mainly focuses on developing query languages and systems to retrieve semistructured data. Relatively less attention has been paid to the manipulation of such data. In order to manipulate such semistructured data, we need a data model that is more expressive than the existing graph-based and tree-based ones to account for the existence of partial and inconsistent information from different data sources. In this paper, we propose such a data model for semistructured data that allows partial and inconsistent information and discuss how to mainipulate such semistructured data.
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