Defining Document Type Definitions provides information about how to use the Stylus Studio DTD editor to define a DTD. Familiarity with DTDs is assumed. This DTD tutorial discusses the following topics:

What Is a DTD?, Creating DTDs, About Editing DTDs, About Modifiers in Element Definitions in DTDs, Editing Elements in DTDs, Editing General Entities and Parameter Entities in DTDs, Inserting White Space in DTDs, Adding Comments to DTDs, About Node Properties in DTDs, Associating an XML Document with an External DTD, Moving an Internal DTD to an External File.

This month, we'll start by revisiting a DTD question that came up in September.

DocBook is a system for writing structured documents using SGML and XML. DocBook provides all the elements you'll need to author and publish technical documents of all kinds. Many computer companies use DocBook for their documentation, as do several Open Source documentation groups. DocBook allows these groups to readily share and exchange information.

XML-based development projects often require the development of a Document Type Definition (DTD), which defines the XML code used in an XML document or application. Even if you are customizing an existing DTD like the DocBook DTD, documenting the DTD is a best practice for a number of reasons, including:

In a presentation at XML Europe 2000, Henry Thompson examined current "best practice" in DTD design and provided a reinterpretation using XML Schemas. The talk focused on the capability of schemas for defining complex types and asserting equivalence among classes of elements.

If you've been developing with XML for even a short period of time, you are likely to have reached the point of wanting to describe your XML data structures. Document Type Definitions (DTDs) and XML Schemas are key technologies in this area.

Many XML developers, just when they've gotten used to DTDs, are hearing about alternatives and wondering what to do with them. W3C schemas, RELAX NG, Schematron -- which should they go with? What will each buy them? What software support does each have? How much of their current systems will they still be able to use? The feeling of unease behind these questions can be summed up with one question: if I leave DTDs behind to use one of the others, will I regret it?

XML.com is pleased to welcome Norman Walsh as a regular columnist on the site. Norm is a Senior Application Analyst at ArborText, Inc., a developer of industrial stength SGML authoring and publishing tools, though we need to say that the words here are his own, not those of his employer. Norm brings a wealth of expertise in SGML, XML, text processing and digital publishing. His column, XML Q&A will cover a variety of topics, dictated by you, the viewer. Please share your questions and suggestions for things you'd like to see covered to xmlqna@xml.com.

The DocBook DTD is a mature SGML DTD for computer documentation, which makes it very useful. The story of its development is also valuable, as it shows what is possible when a group of dedicated people get together to solve a common problem, a thread common to Open Source projects. The development of the DocBook DTD is also a success story that has additional interest to the XML development community; many of those who developed DocBook have gone on to become major contributors to the development of XML.

XML by Example teaches Web developers to make the most of XML with short, self-contained examples every step of the way. The book presumes knowledge of HTML, the Web, Web scripting, and covers such topics as: Document Type Definitions, Namespaces, Parser Debugging, XSL (Extensible Stylesheet Language), and DOM and SAX APIs. At the end, developers will review the concepts taught in the book by building a full, real-world e-commerce application.

XML documents follow a stricter set of rules than HTML. Every open tag must have a corresponding close tag; "empty" tags may use a shorthand form (<.tag/>); XML documents must begin with an XML declaration while the HTML declaration is optional; the HTML declaration doesn't use the <.? ?> notation. These rules, and many more, define a "well-formed" document.

Ever tried to read a DTD, and failed miserably? Ever wondered what all those symbols and weird language constructs meant? Well, fear not - this crash course will get you up to speed with the basics of DTD design in a hurry.If you've been playing with XML for a while, you probably already know that XML documents come in two flavours: well-formed and valid.

Undoubtedly, you've heard about the benefits of managing your data with XML: data will be reusable across multiple applications, tools that understand XML will make your life easier, content producers and presentation specialists will be able to work independently, and so on. Does this really work, or is it just hype?

This introductory article shows how to create XML Document Type Definitions (DTDs) and well-formed, well-defined XML files that can be validated by the XML parser of your choice. While you don't have to include a DTD with every XML file you produce, doing so will make your life a lot easier. Not only will a DTD enforce the syntax you've established for your XML files, it will also allow your files to be parsed by a validating XML parser. Code samples include DTD and XML document examples.

The arrival of any new schema language usually brings a utility to convert DTDs to that language, but using such a utility on a large collection of sophisticated DTDs isn't enough to provide a smooth transition for a big publishing organization. Even if all the DTD developers are trained in the new schema language beforehand, a sudden change in their responsibilities to maintaining their large, complex schemas in the new syntax is impractical.

A Document Type Definition (DTD) is used by SGML applications, e.g. HTML, to specify rules that apply to the markup of documents of a particular type, including a set of element and entity declarations. An XHTML DTD describes in precise, computer-readable language the allowed syntax or grammar of XHTML markup.

Elements, entities, attributes and notations are the building blocks of a DTD. Once you understand what each of these are, you can easily write your own DTD and be on your way to writing XML applications.

Topic: XML -- How to write a DTD. [ XML index ]. ... Defining an XML document type (ie
writing a DTD) consists of the following steps, not necessarily in order: ...

This introductory article shows how to create XML Document Type Definitions (DTDs) and well-formed, well-defined XML files that can be validated by the XML parser of your choice. While you don't have to include a DTD with every XML file you produce, doing so will make your life a lot easier. Not only will a DTD enforce the syntax you've established for your XML files, it will also allow your files to be parsed by a validating XML parser. Code samples include DTD and XML document examples.

For literally years now, authors have been faced with a difficult dilemma: should we write pages to conform to the W3C standards, or write them to account for browser bugs? There are strong cases to be made for either approach. In the former case, your pages will be more likely to work in the future, and are certainly more "pure," but typically browser didn't display them very well. In the latter case, the display was a little more predictable for contemporary browsers, and it was certainly easier to sell to management, but what about the future? Would a new browse r-- one with stricter standards compliance -- break the display of the pages due to their bugwards compatibility?