Issue raised by: Ray Denenberg 15 Jul 1996
The Z39.50 semantics imply that tagSet-M and tagSet-G metadata elements are for use at the record level, and that for individual elements, GRS-1 metadata should be used, for example, for usageRight, rather than the pair of tagSet-M elements defined identically (recordUsage and restriction, tags 8 and 9, used in combination). However, several of the tagSet-M or tagSet-G metadata elements do not have corresponding GRS-1 metadata fields, for example tagSet-G element description (2/17).
When GRS-1 and related definitions and structures were developed, the need envisioned was to be able to apply metadata to an entire record, as well as to individual elements; and GRS-1 metadata was the mechanism developed to apply metadata to an element; however there is no mechanism within GRS-1 to apply metadata to a record, thus the use of tagSet elements such as tagSet-M and tagSet-G was provided as the mechanism to do so.
However, there is no reason that a tagSet-M or tagSet-G (or any other tagSet) element may not or should not be used at the element level. There may be some rules of application or inheritance required within a schema to specify semantics when the same element appears at different nodes on an element tree (but this may also be true when the GRS-1 mechanism is used).