Add service to the glossary

[svrnm]

What are you trying to achieve?

The term service is an important term used at a lot of places within the spec, but there is no definition in the glossary what a service is (and what it is not). Maybe it's somewhere else in the spec and just needs to be referenced?

Additional context.
For example in k8s a service is defined the following:

In Kubernetes, a Service is an abstraction which defines a logical set of Pods and a policy by which to access them (sometimes this pattern is called a micro-service). ([source](https://kubernetes.io/docs/concepts/services-
networking/service/))

Does this definition also apply for OpenTelemetry, so it could be referenced or are there nuances, since a service could also run outside k8s and outside a container?

It would also be good to include:

• what the difference is between a service and a service.instance (following that definition form k8s above a service instance is then one pod in that logical set?)
• what is the difference between a service and an application or are those words synonyms?

(I am happy to come up with a draft for the definition, but I would like to understand first if there is a need or if there is an existing definition that just needs to be linked/moved into the glossary)

[yurishkuro]

If we don't have it elsewhere already (we might) then it's a good thing to have in the glossary. However, it's actually pretty difficult to define holistically, as the types of workloads vary greatly. Eg consider an ML training platform that lets users define training jobs - logically each job is a service, but that doesn't map to k8s definition at all since the actual workers executing the jobs may be shared. I think in my company we at one point defined a service as "something that is built with the same make target".

[svrnm]

There are definitions in the website glossary (maybe it would make sense to have them in sync?):

Application: One or more Services designed for end users or other applications.

Service: A component of an Application. Multiple instances of a Service are typically deployed for high availability and scalability. A Service may be deployed in multiple locations.

These definitions are still recursive but are a starting point.

[ranrib]

There are definitions in the website glossary (maybe it would make sense to have them in sync?):

Application: One or more Services designed for end users or other applications.

Service: A component of an Application. Multiple instances of a Service are typically deployed for high availability and scalability. A Service may be deployed in multiple locations.

These definitions are still recursive but are a starting point.

This is a good definition. I think in general the guideline is that an application comprises 1-n services.

[jsuereth]

I'd be a fan of including this in the specification if you submit a PR adding it.

[svrnm]

Sure! Let me do that.