Category talk:Graph invariants

Invariant, property, parameter

There are slight differences between these, but it is quite difficult to make all of this clear and to know how (and if) the article should distinguish them.

• an invariant is a function assigning some isomorphism-independent value
• a property is of logical order (may be satisfied or not). Bollobás uses the term for collections of graphs (the property is identified with the collection of the graphs satisfying the property)
• a graph parameter is, according to Lovász and Sós, a function defined on finite graphs, invariant under isomorphisms (it is a simple graph parameter if it is only defined on simple graphs)

pom 18:16, 6 October 2006 (UTC)