XML: Document and Information Management

By Todd Freter

Thus far this series of articles about Extensible Markup Language has explored XML's origins, some early potential uses in applications, and its relationship to HTML, the current markup language for documents published on the Web. Another important role for XML is in managing not only documents but also the information components on which documents are based.

Document Management: Organizing Files

Document management as a technology and a discipline has traditionally augmented the capabilities of a computer's file system. By enabling users to characterize their documents, which are usually stored in files, document management systems enable users to store, retrieve, and use their documents more easily and powerfully than they can do within the file system itself.

Long before anyone thought of XML, document management systems were originally developed to help law offices maintain better control over and access to the many documents that legal professionals generate. The basic mechanisms of the first document management systems performed, among others, these simple but powerful tasks:

In essence, document management systems created libraries of documents in a computer system or a network. The document library contained a "card catalog" where the user-supplied information was stored and through which users could find out about the documents and access them. The card catalog was a database that captured information about a document, such as these:

Armed with a database of such information about documents, users could find information in more sensible and intuitive ways than scanning different directories' lists of contents, hoping that a file's name might reveal what the file contained. Many people consider document management systems' first achievement to have created "a file system within the file system."

Soon, document management systems began to provide additional and valuable functionality. By enriching the databases of information about the documents (the metadata), these systems provided these capabilities:

These critical capabilities (among others) of document management systems have proven enormously successful, fueling a multi-billion dollar business led by Documentum, Xerox, IBM, and others.

XML: Managing Document Components

XML and its parent technology, SGML (Standard Generalized Markup Language), provide the foundation for managing not only documents but also the information components of which the documents are composed. This is due to some notable characteristics of XML data.

Documents vs. Files

In XML, documents can be seen independently of files. One document can comprise many files, or one file can contain many documents. This is the distinction described earlier in this series between the physical and logical structure of information. XML data is primarily described by its logical structure. In a logical structure, principal interest is placed on what the pieces of information are and how they relate to each other, and secondary interest is placed on the physical items that constitute the information.

Rather than relying on file headers and other system-specific characteristics of a file as the primary means for understanding and managing information, XML relies on the markup in the data itself. A chapter in a document is not a chapter because it resides in a file called chapter1.doc but because the chapter's content is contained in the <chapter> and </chapter> element tags. Because elements in XML can have attributes, the components of a document can be extensively self-descriptive. For example, in XML you can learn a lot about the chapter without actually reading it if the chapter's markup is rich in attributes, as in <chapter language="English" subject="colonial economics" revision_date="19980623" author="Joan X. Pringle" thesis_advisor="Ramona Winkelhoff">. When the elements carry self-describing metadata with them, systems that understand XML syntax can operate on those elements in useful ways, just like a traditional document management system can. But there is a major difference.

Information vs. Documents

XML markup provides metadata for all components of a document, not merely the object that contains the document itself. This makes the pieces of information that constitute a document just as manageable as the fields of a record in a database. Because XML data follows syntactic rules for well-formedness and proper containment of elements, document management systems that can correctly read and parse XML data can apply the functions of document management system, such as those mentioned above, to any and all information components inside the document.

The focus on information rather than documents from XML offers some important and capabilities:

Representative Products

While the general world of document management is moving toward adoption of structured information and use of XML and SGML, three providers stand out today:

Questions or comments? webmaster@sun.com
Copyright 1994-1998 Sun Microsystems, Inc., 901 San Antonio Road, Palo Alto, CA 94303 USA.
All rights reserved. Legal Terms. Privacy Policy.