Re: [soa-rm-ra] Version

[Francis McCabe <frankmccabe@mac.com>]

Here is why I thought that version was connected to identity:

A resource is a time varying entity that has value to someone (or something)

A version identifies a particular state of the resource at a particular moment in time (could include space too).

The resource may or may not have any 'awareness' of its versions. In fact, I would argue that most of the time it does not. 

Consider a description of a service. That description will have many aspects to it. It may also identify which version of the service the description pertains to.

Now, consider versioning the description itself. In the case of a description, it is a structure artifact and so it may be possible to 'fit' any version identification of the description into the description itself. But, if the description was designed to a specification that neither enabled versioning nor enabled extensions, then you could not embed version info into the description artifact (straw man I now, but other resources have no space for version info).

On the other hand, a repository that held service descriptions is likely to need to handle multiple versions of a description for a given resource. The repository has to be able to distinguish multiple versions of an artifact irrespective of whether that information is embedded within the artifact.

In effect, the repository has to combine the name of the artifact with the version info of the artifact in order to be able to unambiguously identify the correct version of the artifact.

Hence the idea of the version being an aspect of identity rather than a part of the resource itself. Identity is outside the identified entity.

Frank

On Jun 25, 2008, at 8:54 AM, Ken Laskey wrote:

As a refresher of thoughts on the issue, see the attached.

<versioning draft.doc>

On Jun 25, 2008, at 11:50 AM, Duane Nickull wrote:

I think first of all, a version is not a specialized type of identity.

I would roll identity and identifier into one (identifier is the token of
the identity)

Version is an attribute of "resource" IMO.  It usually is denoted with a
major_version.minor_version.release in software but I think it is too
granular so I would just stop at version and not include version identifiers
or date-time string etc.

Duane


On 25/06/08 8:21 AM, "Francis McCabe" <frankmccabe@mac.com> wrote:

This is a just a noodle. But, I was trying to see how versions fitted

with the resource model and came up with ...

Version

An identity associated with a resource that establishes a time and/or

place where the resource is located.

Resources are generally time varying in nature – accessing a resource

at one time will often lead to a different outcome than accessing it

at another time. As a result, it may be necessary to identify a

resource at a point in time – in effect to identify a specific version

of a resource.

Frank

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