When defining a field of a signature to be a relation, you write something like this:
+When defining a field of a signature to be a relation in itself as well , you write something like this:
sig University {
@@ -15,11 +15,11 @@ Multiplicity Markings
}
-Here, each University knows which student is a member of which - professor's research group. That is, there is a relation from - Universities to Students to Professors. By writing multiplicity - markings to the declaration of the relation, we can add additional - constraints in a concise way. For example,
+Here, there is a (nameless) relation from Students to Professors, which is + in turn related to some university through the relation groupMember. + + By writing multiplicity markings to the declaration of the relation, + we can add additional constraints in a concise way. For example,
sig University {
@@ -27,7 +27,7 @@ Multiplicity Markings
}
-means that each student is in exactly one professor's research +
means that each student is in exactly one professor's research group. If we instead wrote this,
@@ -36,8 +36,8 @@-Multiplicity Markings
}
Then we are saying that some students may be in no research group, -but no student is in more than one. Lastly, we can write
+Then we are saying that every student is studying (related) with at most + one professor. Lastly, we can write
sig University {
@@ -45,8 +45,10 @@ Multiplicity Markings
}
-to say that each student is in one or more research groups. When - no multiplicity markings are present, there are not +
to say that each student is in one or more research groups (since the student + can be related with some ie. one or more professors. + + When no multiplicity markings are present, there are no constraints.