subject+an activity tag constraint

[Chafik Graiguer]

I wonder what is the use of this constraint: subject+an activity tag constraint have a prefered or set of preferred rooms ?
is there any example to illustrate it?
deos this mean an activity has to meet two conditions:
- belonging to subject
- has the required tag
?

[Liviu Lalescu]

The activity must have the exact subject and contain the activity tag. Then this activity is constrained to this (these) room(s).

[Volker Dirr]

It was suggested some time ago by me, because i needed it in some cases.
Today it is "unneeded", because:
- today it is possible to add several activity tags to an single activity
- today it is possible to modify subactivities manualy.

so today it is maybe unneeded because you can use one way of the above alternative ways. So maybe this constraint can be deleted someday? But one the other hand it is maybe critical to delete guys that use that constraint today. maybe that constraint is in a few cases faster to enter then the alternative ways.