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HomeRants > Goodbye documents, hello objects! > Modeling informative objects > Create a formal model




How many models?

Why turn to a schema?

Use the formal models to validate

Communicate the structure--and revise

Generate authoring forms from the model

Manage your components

Create a formal model

Based on your analysis of the objects your audience needs, you define a standard structure for each object. You will probably need to develop several of these models:

  • An XML or SGML Document Type Definition (DTD): Defines the high-level content object called a root element, then spells out all the component objects, and, if necessary defines all of those, too.
  • Schema: Does the same thing for XML root elements, but does so in XML.
  • Template: A less formal pattern that comes in many forms, and serves as the basis for transforming content, often through stylesheets.

How many models?

You may want to create quite a few, or, if you make one giant DTD, organize it into modules:

  • Common elements that you can use anywhere, such as paragraph, table, list
  • Common inline elements, such as emphasis, link, or cross reference
  • Publications, such as books, reports, brochures
  • Specific content models such as procedures, concepts

Related info:

eBook: Making an XML DTD Step by Step (PDF, 384K)

Form for Modeling an Object (PDF)

A rhetoric of objects

Complexity theory as a way of understanding the Web

Structuring complex interactive information

Modeling information in electronic space

 Why turn to a schema?

If you need software to check on the type of data entered, as in a conventional database, schemas make this easier.

Schemas, though, are not supported by every tool. Make the vendor prove that their software handles schemas as well as DTDs.

Use the formal models to validate

Every time you create a new object in a particular class, it must conform to the standards you have defined. The parser consults your DTD or schema, and checks to make sure that you have, in fact, followed the rules. If not, you get an error, or downright refusal to display anything.

Using a true XML editor such as FrameMaker 7 or Arbortext Epic lets you check validity as you go. In turn, the need for validation drives you toward software tools that can check, or guarantee valid content.

Communicate the structure--and revise

Create a table of contents or giant outline for all your content. Recognize that the reusable objects will reappear here, there, and everywhere.

This kind of outline gets out of date as soon as you go live. So consider it only a planning document.

For meetings, create diagrams indicating the structure of a particular group's favorite DTDs, so they understand the structures they must now work within. Discuss, and modify.

Generate authoring forms from the model

From the author's point of view, this approach is just "fill in the blanks." Behind the scenes, the software applies the correct XML tags, so that the resulting document is valid and well-formed XML.


  • Authors do not need to know the model.
  • You hide the tags from authors who might be overwhelmed.
  • Forms are OK for short, regular, objects.


  • Professional authors feel constricted, want to see the structure displayed, want to be able to override the structure, then have their efforts validated after working freestyle for a while.
  • Forms do not work for material that stretches over more than a few pages.
  • Forms are fixed; you need a programmer to change one.

Manage your components

Create a database to track and report on questions like these:

  • How many objects have you defined?
  • How many instances do you expect with the higher-level objects (the root elements defined by DTDs, for example, or publications)?
  • Do you have authors assigned to every instance?
  • How many objects, total, are going to be moving through your system on an average day, or in an average week?
  • How many objects will be "live" in the workflow at any one time?

Complete details on how to create a DTD: Making an XML DTD Step by Step


Next: Join the enterprise-wide data model

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