What techniques do you employ to ensure that your data is precisely and unambiguously specified?

Hi Folks,

How carefully do you specify your data? Is it free from ambiguity and misinterpretation?

Although all data should be specified precisely and without ambiguity, the consequences of data being imprecise or ambiguous ranges from minor to catastrophic.  There is a name for the latter data: level 1 data.

      Level 1 (critical) data: the data must be specified 
      precisely with absolutely no ambiguity. For if the data 
      is misinterpreted, then there is a real 
      possibility of a loss of human life or financial,
      political, or personal calamity.

When you create your XML Schemas do you identify the level of the data? For example, do your XML documents contains a <level> element:

    <Document>
            <level>level 1 (critical) data</data>
            ...
      </Document>

Has anyone created an XML Schema for the various levels?

[Key Question:] If you have level 1 data what techniques do you employ to ensure that there is virtually zero chance for the data to be misunderstood or misinterpreted? 

/Roger