I'm just on the task to update packdefinitions for a specific plugin (startrek1e) and noticed, the following behavior:
<crit><field>Info</field><eval>CONTAINS</eval><data>R</data></crit>
is evaluated but
<crit><field>Info</field><eval>IS</eval><data>R</data></crit>
is not. If I combine multiple CONTAINS and/or DOSNTCONTAIN it works as long as I do not reference the same field in the same <kind></kind> multiple times. So
<crit><field>Info</field><eval>CONTAINS</eval><data>R</data></crit>
<crit><field>Name</field><eval>DOESNTCONTAIN</eval><data>*</data></crit>
works well while
<crit><field>Info</field><eval>CONTAINS</eval><data>R</data></crit>
<crit><field>Info</field><eval>DOESNTCONTAIN</eval><data>+</data></crit>
doesn't work.