the type of modification in terms of pre, post and pre and post. The attribute can
have one of the following values:
- "post" (D) - indicates that the data is to a
standard that is after the modification given
- "pre" - indicates that the data is
the initial standard, or to a previous modification standard than the one given
-
"prandpo" - indicates that the data is to a standard that satisfies both a standard
before and after the modification given