[MS SQL SERVER] Create constraints in a cyclic relations

[Lutoslaw]

I have four tables:

Class- a "class"
PK IdClass

Instance- an instance
PK IdInstance
FK IdClass

PropertyDefinitions- definitions of properties of a concept
PK IdPropertyDef
FK IdClass

PropertyValues- values of properites of an instance
FK IdInstance
FK IdPropertyDef

A Class can have properties. Instance can be of a class. I want to save values of properties of each Instance, but I want to prohibit setting properties of an Instance, which are not defined in it's Class. So, a cyclic dependence occurs. How to create a proper constraint in MS Sql Server to prevent a situation, when an instance has values of properties which are not defined in a class? Or maybe I could design a better DB schema? Thanks. EDIT: Here[^] you can find a applicaable part of a DB diagram.

Greetings - Jacek