How do Agent Group Filters work in the context of Business Transaction?

We have a requirement to ensure that our Business Transaction related measures are calculated only for specific monitored systems (i.e., applications - not that I use the term "application" in the genral sense here, not in the sense of the Dynatrace Application configuration). In our production environment we have many applications configured in one profile – hence it is important that the BTs are filtered in a way that we can guarantee that we do not, due to insufficiently specific filters, mix transactions from different applications.

If general we have filtered our measures by Agent Group, since this ensures that we only measure data related to a specific monitored system. However, in the case of the configuration of Business Transaction filter measures, the filter by Agent Group option is grayed out. As a result, it is possible that some PurePaths not related to the intended monitored system could be included in the BT. It is, however, possible to add such a filter on the BT result measures.

We have two questions related to this:

• Why is the filter by agent group not available when configuring the BT’s filter measure? I can understand that a PurePath may traverse many Agent Groups, but why can we not restrict the evaluation to PurePaths that either start in a specific Agent Group or traverse a specific Agent Group?
• Why, since we cannot implement an Agent Group filter on the BT filter measure, are we able to do this on the BT results, and what does this filtering actually do… i.e., if the filter is set to a specific Agent Group does that mean that:
  • The analyzed PurePaths are restricted to those that start in the selected Agent Group?
  • The analyzed PurePaths are restricted to those that traverse the selected Agent Group at some point?