We consider the recently proposed XQL language, which is designed to query XML documents by content and structure. We show that an already existing model, namely ``Proximal Nodes??, is the only one that addresses all the complex querying operations defined by XQL and that suggests an efficient implementation for them.

We believe that XML query languages can dramatically increase the utility of XML documents by providing powerful and convenient access to the information they contain. As more and more of our critical data is stored in XML documents, presented as XML documents through middleware, or made accessible via XML-oriented APIs, the ability to query XML documents becomes an essential aspect of being able to use the information we have. XQL is a query language based on the structure of XML documents. It is simple, easy to implement, and powerful. This paper explores scenarios in which XML queries might be performed, and presents a tutorial for the XQL query language.

Today, XML is used in three different ways. First, XML is used as a markup language, where documents are considered to be trees (with the occasional hyper link added) which represent the document structure. Secondly, XML is used as an interchange format for structured data. Here, a document is considered as a set of fields, each of which has a specific data type. The third aspect is to use XML to represent text, where a document consists of words which can be stemmed and phrases and the like.

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