This sentence uses white space to separate words.
Thissentenceuseswhitespacetoseparatewords.
Unless you tag every word, that white space has meaning. It is
not purely presentational.
Similarly with other uses of white space: if one represented by
tagging everything white space can be used for, you wouldn't
need it. But in a small tag set such as HTML, you can't get
along without it. Even in a large SGML DTD provision is not
made for all the things one might use white space for,
meaningfully.
Regards,
-- Terry Allen (terry@ora.com) Editor, Digital Media Group O'Reilly & Associates, Inc. Sebastopol, Calif., 95472