Extending XML-RL with update

Abstract

With the extensive use of XML in applications over the Web, how to update XML data is becoming an important issue because the role of XML has expanded beyond traditional applications, in which XML is used as a mean for data representation and exchange on the Web. This paper presents a novel declarative XML update language, which is an extension of the XML-RL query language. Compared with other existing XML update languages, it has the following features. First, it is the only XML data manipulation language based on a higher data model. All of the other update languages adopt so-called graph-based or tree-based data models. Therefore, update requests can be expressed in a more intuitive and natural way in our language than in the other languages. Second, our language is designed to deal with ordered and unordered data. Some of the existing languages cannot handle the order of documents. Third, our language can express complex update requests at multiple level in a hierarchy in a simple and fast way. Some existing languages have to express such complex requests in nested updates, which is too complicated and nonintuitive to comprehend for end users. Fourth, our language directly supports the functionality of updating complex objects while all other update language do not support these operations. Lastly, most of existing languages use rename to modify attribute and element names, which is a different way from updates on value. Our language modifies tag names, values, and objects in a unified way by the introduction of three kinds of logical binding variables: object variables, value variables, and name variables. The powerful ability of our language is shown by various examples.