Common examples of document markup include font family and font size. Markup that represents a procedure for output devices is often referred to as procedural output. For example, when we use a word processor we choose fonts, boldness, and location of text on the page. For example, both quotations and emphasized words may be italicized, even though a quotation has a different function than an emphasis. Procedural markup is time-consuming and requires a significant amount of operator training.
Procedural markup is inflexible.
When a change to a formatting convention is applied, it requires the manual change of all elements in the document that are affected. Unlike procedural markup, generalized markup is not concerned with formatting. This descriptive markup needs to be done only once and will apply to all future processing. Markup should be formally defined. With this formal definition of markup, external programs can be used to process the document.