Network-Oriented Document Abstraction Language: Structure and Reference for the Rest of the Web

The Web has amply demonstrated the benefits of an infrastructure that makes publishing and reference of semi-structured information easily accessible, but in many cases reference and reuse of such information is only at the level of complete files. The potential for greater benefits that may derive from sub-document structure and reference is currently being explored, but this exploration is limited by the fact that such references can only be used with a portion of the Web's content (i.e. that encoded in XML). We have developed a system, the Network-Oriented Document Abstraction Language (NODAL), that is designed to provide a common data model, schema language and sub-document reference system for web-accessible documents or databases encoded in any format (e.g. images, PDF or Word documents etc.). This system thus provides a common reference and access environment for all structured, semi-structured and unstructured data. In this paper, we describe the data model, schema language and URI-based reference language for NODAL and compare it with XML and other systems. Finally, we outline a number of ways that this system can be extended to allow for composition, synchronization and reuse of documents and databases and can thus form a hypertextual foundation for interactive application development without inhibiting interoperability with existing systems. In essence, with NODAL we can bring the benefits of markup and hypertext to all data formats.