I have two device groups and want to create a third group that's the set of devices from group 1 that is not also in group 2. 

Group 1 is all routers and switches.

Group 2 is a sub-set that includes at least one model of each device type in the network.

I want a third group that is the set of all devices other than those in Group 2 (i.e. Group 3 = Group 1 - Group2).  Expressing it as boolean, I'd like

!(G1 && G2)

According to boolean logic rules, this is equivalent to

(!G1 || !G2)

Both require the 'not' operator, which I don't see in the documentation.  Is there a way to do what I need?  There are 600 devices in G1 and 30 in G2.  There isn't a common naming scheme that allows me to identify the members of G3 other than excluding the members of G2 from G1.  Thanks!

All of our device groups definitions were migrated from 2.x to 3.x to 4.x but when I display their membership criteria, they still use the same syntax as before, which doesn't resemble yours.

Why won't something like this work?

memberOf ["G1"] and not memberOf ["G2"] and $Assurance > 75

Sorry, I was using boolean syntax instead of NetMRI syntax, because I don't see that NetMRI offers what's required.

Specifically, I don't see a 'not' operator, which is what I need.  I would like to use a syntax of:

not (memberOf ["G1"] and memberOf ["G2"])

Is the 'not' operator available?

The online docs say:

Logical Operators

The following logical operators can be used to combine comparison sub-expressions:

and, &, &&   boolean AND

or, |, ||    boolean OR

(, )         grouping

Examples:

$Vendor eq "Cisco" and $Type eq "Router"

($Vendor eq "Juniper" and $Type eq "Router")
or ($Vendor eq "Cisco" and $Type in ["Router", "Switch"])

memberOf ["Routing Group”"] and $IPAddress in [10.1.0.0/16, 10.2.3.45]

I agree that the doc doesn't list "not" as a logical operator for that.  So try it and see if it works? 

Or use this instead:

(memberOf ["G1"] and not memberOf ["G2"]) or (memberOf ["G2"] and not memberOf ["G1"])

Can you post the syntax for each of your groups?

Group 1 has devices with names starting with 3 digits and a hyphen.  It contains 605 devices:

$Name like /^[0-9][0-9][0-9]-.*/ and
$Type not like /unknown/

Group 2 consists of specific devices.  It contains 33 devices:

memberOf ["G1"] and
( $Name like /^016-.*/ or
 $Name like /^493-.*/ or
 $Name like /^166-.*/ or
 $Name like /^393-.*/ or
 $Name like /^355-.*/ or
 $Name like /^531-.*/ or
 $Name like /^499-.*/ or
 $Name like /^022-.*/ or
 $Name like /^030-.*/ )

For G3, I tried the following, which gave me the same set as G1, or 605 devices:

memberOf ["G1"] and ($Name not like /^016-.*/ or
$Name not like /^493-.*/ or
$Name not like /^166-.*/ or
$Name not like /^393-.*/ or
$Name not like /^355-.*/ or
$Name not like /^531-.*/ or
$Name not like /^499-.*/ or
$Name not like /^022-.*/ or
$Name not like /^030-.*/ or
$Name not like /^406-.*/ )

I tried this and it worked as marty thought it would :)

memberOf ["Routing"] and not memberOf ["Switching"]

"not memberOf" is a valid comparison operator.  I just did a quick test with these definitions:

Group1: $IPAddress in [192.168.0.0/16]

Group2: $Vendor eq "Cisco"

Group3: memberOf ["Group1"] and not memberOf ["Test2"]

and it worked as expected, with Group3 containing all non-Cisco devices with 192.168.0.x addresses.

Cool!  I'll work with that. Thanks!

Try this one, where two groups are to be aggregated with an 'or' clause and the result of that is to be omitted from the "all devices" group.

memberOf["All Devices"] and not (memberOf["Config Update Pass 1"] or memberOf["Config Update Pass 2"])

The error says "Invalid value 'not'."

However, if I create a fourth group that's Config Update Pass 1 and Config Update Pass 2, then this syntax works:

memberOf["All Devices"] and not memberOf["Config Update Pass 1and2"]

That is correct.  NetMRI does not recognize "not" as a boolean operator -- rather, both "memberOf" and "not memberOf" are recognized as comparison operators.

In your example, I think this would work:

memberOf ["All Devices] and not memberOf ["Config Update Pass 1", "Config Update Pass 2"]