How do we define...As a Service...

With the ...as a service... model picking up we have Infra-as-a-service, Integration-as-a-service..what not. So what would constitute this 'service'? In my view, Service can be defined / made up of
1. The value or benefit that it offers to the consumers like infra, integration, data etc
2. Offered at a mutual agreed quality (QoS parameters such as Performance, security, Availability etc)
3. through a defined interface or access point
4. priced based on the type and/or volume of usage
Now this does not really talk about the location of the service yet. So this means the service could actually be coming out of one of the servers within the organization and be consumed by users of the same organization. So when we talk about cloud computing, 'as-a-service' is a necessary condition but not a sufficient one!