Using guarantee terms, we can either ask an AgreementFactory to provide us service adhering to those guarantees or to 
manage a service according to the relative importance of guarantees with respect to each other. 

In the first case, the agreement factory must be capable of assessing required capacity. 

In the second case, it can work according to a best effort approach - but keeping in mind which guarantee is most 
important and failing it first. This applies typically to GuaranteeTerms with Imporatnce business value.

GuaranteeTerms work well for both cases. However, we should describe this better in the specification. This allows us to
 apply WS-Agreement also to best effort systems, which are prevalent today. 

If we think it is necessary, we can introduce an attribute "BestEffort" to indicate exactly what is expected.