Sean McGrath - XML processing with Python

Open Information Management (OIM) means managing information so that it is open to processing by any program, not just the program that created it. That extends even to application programs not conceived of at the time the information was created.

OIM is based on the principle of data independence: data should be stored in computers in non-proprietary, genuinely standardized representations. And that applies even when the data is the content of a document. Its representation should distinguish the innate information from the proprietary codes of document processing programs and the artifacts of particular presentation styles.

Business data baseswhich rigorously separate the real data from the input forms and output reportsachieved data independence decades ago. But documents, unlike business data, have historically been created in the context of a particular output presentation style. So for document data, independence was largely unachievable until recently.

That is doubly unfortunate. It is unfortunate because documents are a far more significant repository of humanity's information. And documents can contain significantly richer information structures than data bases.

It is also unfortunate because the need for OIM of documents is greater now than ever. The demands of repurposing require that information be deliverable in multiple formats: paper-based, online, multimedia, hypermedia. And information must now be delivered through multiple channels: traditional bookstores and libraries, the World Wide Web, corporate intranets and extranets. In the latter modes, what starts as data base data may become a document for browsing, but then may need to be reused by the reader as data.

Fortunately, in the past ten years a technology has emerged that extends to documents the data base's capacity for data independence. And it does so without the data base's restrictions on structural freedom. That technology is the Standard Generalized Markup Language (SGML), an official International Standard (ISO 8879) that has been adopted by the world's largest producers of documents and by the World Wide Web.

With SGML, organizations in government, aerospace, airlines, automotive, electronics, computers, and publishing (to name a few) have freed their documents from hostage relationships to processing software. SGML coexists with graphics, multimedia, and other data standards needed for OIM and acts as the framework that relates objects in the other formats to one another and to SGML documents.

The World Wide Web's HTML and XML are both based on SGML. HTML is a particular, though very general, application of SGML, like those for the above industries. There is a limited set of markup tags that can be used with HTML. XML, in contrast, is a simplified subset of SGML facilities that, like full SGML, can be used with any set of tags. You can literally create your own markup language with XML.

As the enabling standard for OIM of documents, the SGML family of standards necessarily plays a leading role in this series. We provide tutorials on SGML, XML, and other key standards and the techniques for applying them. Our books vary in technical intensity from programming techniques for software developers to the business justification of OIM for enterprise executives. We share the practical experience of organizations and individuals who have applied the techniques of OIM in environments ranging from immense industrial publishing projects to websites of all sizes.

Our authors are expert practitioners in their subject matter, not writers hired to cover a hot topic. They bring insight and understanding that can only come from real-world experience. Moreover, they practice what they preach about standardization. Their books share a common standards-based vocabulary. In this way, knowledge gained from one book in the series is directly applicable when reading another, or the standards themselves. This is just one of the ways in which we strive for the utmost technical accuracy and consistency with the OIM standards.

And we also strive for a sense of excitement and fun. After all, the challenge of OIMpreserving information from the ravages of technology while exploiting its benefitsis one of the great intellectual adventures of our age. I'm sure you'll find this series to be a knowledgeable and reliable guide on that adventure.