When setting up a relationship class, it would be nice if a definition query or filter could be applied. For example, I have a layer of polygon that contains bituminous, concrete and gravel surfaces. I also have a table of maintenance history for the bituminous only. I have the two related and it sometime causes issues when a user adds a related record from the attribute editor or when accessing the related table some other way such as through identify.
There are workarounds that can achieve the above within an MXD, but they don't mitigate a user accessing the data base directly and bringing unfiltered data.
