Learning XML

2.8. Getting the Most out of Markup

These days, more and more software vendors are claiming that their products are "XML-compliant." This sounds impressive, but is it really something to be excited about? Certainly, well-formed XML guarantees some minimum standards for data quality; however, that isn't the whole story. XML is not itself a language, but a set of rules for designing markup languages. Therefore, until you see what kind of language the vendors have created for their products, you should greet such claims with cautious optimism.

The truth is, many XML-derived markup languages are atrocious. Often, developers don't put much thought into the structure of the document data, and their markup ends up looking like the same disorganized native data files with different tags. A good markup language has a thoughtful design, makes good use of containers and attributes, names objects clearly, and has a logical hierarchical structure.

Here's a case in point. A well-known desktop publishing program can output its data as XML. However, it has a serious problem that limits its usefulness: the hierarchical structure is very flat. There are no sections or divisions to contain paragraphs and smaller sections; all paragraphs are on the same level, and section heads are just glorified paragraphs. Compare that to an XML language such as DocBook (see Section 2.9 later in this chapter), which uses nested elements to represent relationships: that is, to make it clear that regions of text ...