the so-called authority we have referred to earlier. It should be noted that such
authority does not necessarily follow from the publication of a standard by a national
or international body. In fact, many standards applying to software design are put
forth as suggestive measures, rather than obligatory. The authority of a standard (or
a guideline, for that matter) can only be determined from its use in practice. Some
software products become de facto standards long before any formal standards document
is published (for example, the X windowing system).