Hi, Still for my descriptor (attribute). I defined a similarity matrix in the class side. I've never used Magritte to edit class inst var, so out of curiosity, what accessor would you use ? I've use a Block Accessor. (MABlockAccessor read: [ :model | model class matrix] write: [ :model :object | model class matrix: aMatrix]); Is it ok to edit class side inst var ? What would you use ? Also, I was doing a matrix description, but I saw MATableModel and MATableComponent... it seems to be a "matrix", isnt'it ? Thanks Cédrick