Concepts maps is one of tools used in computer aided knowledge assessment. It is a graph with its nodes representing concepts and links between those nodes representig relations between those concepts. There are six main relations that can be used in concept maps: "part- of", "kind of", "is- a", "atribute", "value". Not only connection between each two concepts is important, but also the fit of this fragment into the map as a whole. To make the concept map based assessment process more automated it is useful to study which combinations of concepts and relationships are allowed and which are not. This paper considers relation "attribute" and its combinations with other relations.