• Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

15. XML > Conditional Sections

Conditional Sections

As we mentioned earlier in this chapter, XML lets you include or ignore whole sections of your DTD, so you can tailor the language for alternative uses. The HTML DTD, for instance, defines transitional, strict, and frame-based versions of the language. DTD authors can select the portions of the DTD they plan to include or ignore by using XML conditional directives:

<![INCLUDE [
   ...any XML content...
]]>

or:

<![IGNORE [
   ...any XML content...
]]>

The XML processor either includes or ignores the contents, respectively. Conditional sections may be nested, with the caveat that all sections contained within an ignored section are ignored, even if they are set to be included.

You rarely see a DTD with the INCLUDE and IGNORE keywords spelled out. Instead, you see parameter entities that document why the section is being included or ignored. Suppose you are creating a DTD to exchange construction plans among builders. Since you have an international customer base, you build a DTD that can handle both U.S. and metric units. You might define two parameter entities, thusly:


PREVIEW

                                                                          

Not a subscriber?

Start A Free Trial


  
  • Creative Edge
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint