The location are paramters u and v and the combination needs to be unique. What does not work is that I set u and v unique individually. After all (1,0) and (1,1) are diffent locations, but they have a common u, namely u=1, so it is not unique.

I solved this by defining a location as a string '(u,v)'  instead of 2 parameters. 

But I want to know how I can retrieve u and v from the string '(u,v)'  regex (\d+,\d+) 

or go back to two parameters, but add a check for unique of the combi?

Each way is okay for me.

In both cases, you can extract the u and v parameters with a regex translator. I'd drop the parentheses, to save the user having to read and type them all the time, and maybe allow whitespace after the comma:

to '%u /(\d+),\s*\d+/ $$1' endto to '%v /\d+,\s*(\d+)/ $$1' endto @u = :Location%u  @v = :Location%v 'u is ' @u ' and v is ' @v

To make sure the users follow the legal format for Location, you can add a corresponding Regex to the property type, \d+,\s*\d+. (If you want to allow decimals, scientific notation etc., just extend \d as desired.)

If on the other hand you want to keep u and v separate, and it's OK just to show an error / warning in the model if values aren't unique, see http://www.metacase.com/support/55/manuals/mwb/Mw-6_7_4.html" rel="nofollow - 6.7.4 Checking instance uniqueness in the Workbench User Guide. If you define an Identifier Generator for the Cell object type, outputting both u and v (e.g. :u ',' :v), those examples should work as-is.

That worked. Was looking through the documentation for regex but could not really fnd it. 

Had to look for translaters instead, that works good.