Figure 4: Illustration of Service Instance creation engine [6] 

Again, what is clear is the idea that services are composed of components and some method 

is required that can provide an overall view of the service performance. The focus is on how 

the service performs overall. 

2.4 Service Level Agreements 

2.4.1 Overview of Service Level Agreements 

Bearing in mind what has been discussed in the previous sections, the first point to be made 

clear is that customers do not care how a service is composed    to them the quality of the 

end service is what is important [12]. Generally a Service Level Agreement can be defined 

as a contract between a Service Provider and a Customer that guarantees specific levels of 

performance and reliability at a certain cost [12]. Typically the Service Provider is the party 

providing a service and the Customer is the party paying for and receiving the service and 

for any one SLA there will be a customer and a service provider. 

"