The impact of SGML and XML on computing in the humanities is wellknown. Markup languages have been used on such diverse texts as Nordic runes (Driscoll °), to the Oxford English Dictionary(New OED and Text Research°. Substantial experience has been gained in the application of markup languages to diverse texts with corresponding gains in the usefulness of such texts for computing humanists. The default use of SGML for the representation of only one hierarchy, and the explicit prohibition of overlapping elements in XML, has posed considerable limitations to humanists attempting to record their observations of multiple overlapping hierarchies in textual materials. Several approaches have addressed these limitations, ranging from milestone elements(TEI), stand-off markup to record hierarchies (Thomspon 1997°), fragmentation of a base text (TEI), to the development of non-SGML/XML markup languages which will require special processing software TexMECS: New meta-language for recording multiple hierarchies (Sperberg-McQueen and Huitfeldt 2001°).All of these approaches suffer from a variety of limitations and problems. The most notable problem is a lack of commonly available software to create and make the overlapping hierarchies available to scholarly investigation. Durusau and O'Donnell (2001°) present a method for recording overlapping hierarchies using XML standards, particularly XPath and XSLT. The essential insight is that the key piece of information in encoding a complex text is membership of a particular piece of text (PCDATA in SGML/XML terminology) in a given hierarchy, and not its surface representation through markup. Whether this membership information is represented in a conventional SGML/XML "tree" or by some other means, it is the information that is of interest to the computing humanist. This technique relies upon the use of XPath syntax to record the hierarchy information for atoms of text in a larger work. For example:
<w id="w1" sn:clauses="/clauses/clause[1][@id='c1']/s[1]/w[1]" tx:text="/text/para[1][@id='p1']/w[1]" pg:pages="/pages/page[1][@id='p1']/line[1][@id='l1']/w[1]" >This</w> Durusau and O'Donnell demonstrated the use XSLT to construct and then query overlapping hierarchies of XML markup on a base text.The theory and practice of querying of XML documents has been under rapid development at the World Wide Web Consortium (XQuery°). Despite that pace of development, there has been no systematic investigation of querying texts across multiple hierarchies. However, most of the techniques currently under development recognize the importance of XPath syntax on the effective formulation of an XML query language. To develop effective querying of XML documents across multiple hierarchies, Durusau and O'Donnell are developing techniques to visually present overlapping hierarchies to allow "discovery" of fruitful lines of investigation for particular texts. XSLT andSVG are used for this purpose. Overlapping hierarchies may well exist for a text that are of no interest to one researcher that are the focus of research for another. The ability to effectively choose which hierarchies are of interest will be crucial to effective use of overlapping hierarchies recorded for a particular text. In addition to allowing a separation of hierarchies of interest from those that are not, the visual presentation of overlapping hierarchies is also the first step towards addressing the need for intimate knowledge of the underlying markup to formulate a query for the multiple hierarchies recorded using this technique. Effective queries now require mastery of the various hierarchies and a working knowledge of their relationships, one to the other, in order to obtain any predictable results. With an entirely visual presentation of the overlapping hierarchies, scholars will be able to choose the hierarchies by display and not markup syntax, as being the subject(s) of further analysis. This paper demonstrates the use of XSLT and SVG to produce visual representations of documents with overlapping hierarchies and the linking of these visualizations to XPath and XQuery statements. Multiple editions, annotations and analyses of Book 1 of Milton's Paradise Lost form the test case for these techniques. The more detailed the analysis the greater the need for detailed knowledge of the syntax but that will be only after the scholar has found information of interest and not a general exercise in mastering several divergent markup regimes. This will be of particular importance with many texts such as biblical texts that have complex syntax, grammatical, literary and transmission hierarchies that overlap and combine in complex ways.