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Last modified: March 10, 2001
XML Document Navigation Language (XDNL)

[March 10, 2001] On March 15, 2000, NEC Corporation submitted a Note on the XML Document Navigation Language (XDNL) to W3C.

Document abstract: "With the diversity of accessing devices, WWW content needs to be designed for both PC and non-PC devices, so that it can be appropriately navigated and rendered by each type of devices. This note focuses on the navigation of content which helps the user to easily browse a huge document on relatively small devices. The general idea of navigation is explained, and a new language, the XML Document Navigation Language (XDNL) is proposed in this note."

Rationale and description: "With the diversity of WWW accessing devices, it is desirable to present same WWW content in different forms so that the content can be displayed on various types of devices. A general method to realize this is to divide the content into two parts: the data and its presentation defining how the data is shown. Presentation of WWW content has two aspects: in which order portions of information are shown and in what style each portion of information is displayed. The latter presentation is well discussed in the stylesheet activity, while the former is not. This note focuses on the former presentation and introduces the idea of Navigation. This note also proposes the navigation language, XDNL... An XDNL document is an XML document. It consists of multiple blocks, each of which is a set of instructions to create leaf-documents of a specific type. Each set of instructions may be applied to different portions of an original document tree, thus creating a series of leaf-documents of the same type... Navigation is a set of instructions to create an appropriate flow of a document for each type of devices. A navigation language which specifies this set of instructions should describe: (1) which portion of a document is shown at each time, as a leaf-document, (2) from/to which leaf-document a flow-link should traverse... Separating Navigation from Style will improve the legibility of both Style and Navigation, otherwise it will be hard to tell the flow or view of a document from the complicated and tangled description of stylesheet. It will also improve the re-usability of Style and Navigation. For example, when there are two types of client devices with the same screen size but different color depth, it will be possible to use the same Navigation to process a document for two types of devices, while it may be necessary to use two different kinds of Style."

From the staff comments: "XDNL has a lot of similarities with XSLT, and mostly uses the syntax of XSLT and XPath. There are three main features found in XDNL that are not available in XSLT: (1) To generate multiple output documents from a single input document (similar to an XSLT extension in XT) (2) To limit the size of each generated document by text size or by the number of elements copied. This is especially useful for creating documents for devices which have a small memory. (3) To easily create conditional links, e.g. to avoid creating a link to the 'previous' document in the first document of a sequence. The submitters note that document reorganization ('navigation') and styling should be separated, and that therefore a separate language for navigation should be developed. The similarities of XDNL and XSLT, and the frequent use of XSLT for transformations not related to styling, suggest that it may as well be possible to use one and the same language in a two-step process. For handling the diversity of various Web browsers, the HTML Working Group is currently developing a modularized version of XHTML (Modularized XHTML). Using document profiles and CC/PP device capability negotiation, the same document can be viewed from various devices including PCs, mobile phones, PDAs and TVs. In this respect, modularized XHTML and XDNL address different parts of the same problem. Modularized XHTML addresses the problem of HTML documents themselves which can be viewed by various devices, whereas XDNL addresses the problem of how to generate such documents... The XSL Working Group is invited to investigate whether and how the ideas presented in the XDNL submission can be integrated into a potential next version of XSLT or can be made available as extensions. The HTML Working Group, the CC/PP Working Group, and the Mobile Access Interest Group are invited to comment on the XDNL submission from their viewpoints."


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