Design issues of XTQ language

With the rapid spread of XML documents over the Internet, many XML query languages are proposed to query XML documents to extract and restructure information. XQuery and XPath become the most promising standard. However, XML document is a tree structure by nature. XPath can only address a path rather than a subtree so it makes queries lengthy and difficult to parse and optimize. In this paper, we introduce a new query language called XTQ and discuss its design issues. XTQ is based on logic XTree, an extension of XPath, which overcomes the limitations of XPath and XQuery. Using XTree expression, XTQ can exhibit a compact and convenient programming style by making a pattern matching query over tree fragments of XML document. To make XTQ a practical language, we introduce many new features into it based on previous works. The major parts of these features, including query, conditions and constructions, are introduced in this paper.