The Definition of Service

Recall the definition I provided for the term service:
* A service is the performance of work for others.

In general, entities (people and organizations) create capabilities to solve or support a solution for the problems they face in the course of their business. I think it fair to say that some of these capabilities are core competencies. They might even create competitive advantages in the marketplace. SOA isn't fundamentally about creating new capabilities; it is about business services as the key organizing principles that drive the design of IT. What is the driver? Alignment with business needs.

So how does this tie back to definition of service? SOA is a way to organize the world around the concept of work performed for others. How is 'work' defined? By business needs. What world is organized? The performance of work, ostensibly implemented with IT assets. Notice I still express service as an act as opposed to an object. It is easy to think of a service as a thing (such as a web service). The difficulty with that approach is then differentiating between the capability (work performed) and the service. It also leaves unanswered chicken and egg questions like "if a service isn't invoked, does it exist" and "once interaction with a service is complete, does the service cease to exist" and " if there is no description of the service, is there a service"?

Ultimately, there are capabilities and there are needs. An example: let's say I have a catering company. You would like to have a dinner party catered. I offer my catering services for you. I perform the work of catering and you realize the benefit. The service is the act of me catering your party. I may describe the service beforehand in promotional materials (lets say); we most likely will negotiate and commit to a contract that establishs our shared expectations; and there will be an exchange of value - mostly likely because I will charge a fee for the service I offer.

Until I actually cater your dinner party, there is no service. There is potential for a service and an expectation of a service, but it boils down to the fact that the service is an act.

In general, my catering company offered a capability to serve or support a solution for someone else's problem. As such, I provide a service. My consumers have needs which may be satisfied by that capability.

Back the definition service within the context of SOA:

What I've seen and what I've read and what I've experienced is that service as a word is used as a unifier for the following related ideas:

1) The offer to perform work for others
2) The specification of the work offered for others
3) The software used as a tool to implement a capability performed for others
-as well as -
4) The performance of work for others

How do these other ideas relate to service?
1) The concept of an offer in inherent to a service. On a notional timeline, if work is performed for others, there must be an offer to do so. It may be formal, it may be informal, it may be explicit, it may be implicit, it may not follow a publish-find-bind paradigm of offer. But an offer must be made by some entity that will perform the work. In general terms, I would say that an offer is a proposal which is made by some entity may so to address a need.
2) A specification is a description of the work/capability. Remember the definition considers the act . Therefore, the description focuses on interfaces and behavior to support interaction between two entities: one with a capability and one with a need.
3) Here is where most definitions of service within SOA go. I don't disagree that this is an important aspect to consider. However, I think that terming this concept 'service' is wrong.

I pulled these thoughts together as I mused a question on one of my earlier posts on the SOA-RM mailing list. Here's the text of my email:

"We seem to be starting to head back to the service as an object as opposed to an act. I still do not believe that a service is an ‘object.’ In fact, I believe that assumption has caused much of the difficulty in figuring out what a service actually is.

What is invoked is a capability, consistent with the execution context and so to produce real world effects. The actual invocation and performance of the capability is the service; i.e. the action. Hence I maintain that visibility, interaction and effect are the interrelated concepts often (yet confusingly) referred to with a shorthand nomenclature of ‘service.’

As far as roles go, the very essence of the word service is the recognition that does for . I would agree that any other specification of this generalization (uh…isn’t that an ontology) belongs in something other than the RM. "

The question I received was: "What about defining service as the potential of an act? if I understand what you are saying here, it would imply that a service is not a service until it is actually performing an action. During the time that it is "waiting" to perform an action it is not a service, nor is it after it has completed the action it was created to do."

Right now, my best answer is: the implication is correct because is a service is an act, not an object, and we're again seeing a confuddling of ideas.

Ok. If anyone stumbles upon these initial posts, I'd love to hear addtional thoughts.