This feature would allow group definitions to pivot on a value substring specified as a regex submatch. The basic idea is to be able to pivot on information embedded within values such as hostname, ip, etc. For example, if business unit is encoded into hostnames at company X and they want to see all JBAS servers by business unit this currently can't be done with a single group definition. IT can be done with one GD per business unit, with each GD narrowing it's resulting single group with a "contains" type operation. For example, if we had two business units each with two machines:

BU01-Machine01
BU01-Machine02

BU02-Machine01
BU02-Machine01

today:

resource.type.plugin = JBossAS
resource.type.name = JBossAS Server
resource.parent.type.plugin = Platforms
resource.parent.type.category = PLATFORM
resource.parent.trait[Hostname] contains = BU01


resource.type.plugin = JBossAS
resource.type.name = JBossAS Server
resource.parent.type.plugin = Platforms
resource.parent.type.category = PLATFORM
resource.parent.trait[Hostname] contains = BU02

The proposal is for something like:

resource.type.plugin = JBossAS
resource.type.name = JBossAS Server
resource.parent.type.plugin = Platforms
resource.parent.type.category = PLATFORM
groupby resource.parent.trait[Hostname] matching (BU\d\d)-Machine\d\d

So, the group by would work not just on distinct values of a specified value set, but distinct portions of those values.