Hi The purpose or PRMeta is to add meta information to structure... "additional fields to any structure (sort of a replacement of Pier-Form)" . Is it this kind of extension that could help resize picture for instance (we add 2 Number that describe height and weight). I don't see really well how to use them. Can you provide me a simple example ? What is the way to use these meta variables in computation ? Also, would PRMeta extensions to PRStructure could be added to MADescription ? I want to make a description wich is basically a single option description, except that I'd like to extend the description with a symetric matrix that held comparison similarity numbers. For instance, let's consider an attribute weatherCondition, it's options are: (excellent, good, bad, extreme). Let say, I have the following comparison matrix for the attribute weatherCondition: excellent good bad extreme excellent 1 0.8 0.1 0 good 1 0.2 0 bad 1 0.7 extreme 1 so that: similarityBetween: 'good' and: 'bad' returns 0.2 I'd like to attach this matrix to the description, and was thinkink an extension like meta could do it. It will allow me to edit the similarity matrix too (sort of edit meta like in pier). If you see any obvious alternative to do what I want, please tell me, but I find this could be nicey done with Magritte. Thanks Cédrick