Identifiers 2.0 new internal WD

[Norman Gray]

Marco, hello.

> On 2015 May 13, at 08:45, Marco Molinaro <molinaro at oats.inaf.it> wrote:
> 
> 2015-05-12 18:49 GMT+02:00 Norman Gray <norman at astro.gla.ac.uk>:
> [...long cut...]
>> Sect. 3: 'that is, IVORNs should not be reused.' This rules out an IVORN which refers to 'today's weather', unless you decide that 'today's weather' is a single logical resource even thought the referent -- the data it is referring to, as opposed to its description -- changes from day to day.  Is that intentional?  I think such an IVORN _should_ be permitted, by the way.
> 
> I'm not sure I get the clash described by your example.
> An IVORN for a "today's weather" resource will remain the same,
> changing resource content or description, as also allowed (Sect.3,
> directly after):
> 
> "The description of the resource referred to by the identifier,
> however, MAY change over time."

I think I was a little elliptical, sorry.

Consider for example an IVORN like ivo://norman/weather?2015-05-13.  Its value might be 14 degrees, and its description 'today's weather'.  Tomorrow, I will have to change its description to 'yesterday's weather', but its name will remain ivo://norman/weather?2015-05-13, and its value will remain 14 degrees even if we have a heat-wave (20 degrees -- the human body can't stand it!!).

If, on the other hand, I have a resource ivo;//norman/weather?today, then its value today will be 14 degrees, and its description will be 'today's weather', but its _value_ tomorrow (as opposed to its description) will change.

So, presuming that the 'logical resource' here is the value 14 degrees (in practice, presumably a larger dataset), is this  resource ivo://norman/weather?today conformant with the prescription 'Furthermore, the identifier SHOULD refer to at most one logical resource over all time; that is, IVORNs should not be reused.'?  Or, put another way, what is a 'logical resource' (the term appears only here)?

I think it would be reasonable to permit this (or at least unreasonable to forbid it at this level), but I could read the text here as forbidding it _or_ permitting it.  Of course, we wouldn't want people to re-use identifiers which have simply fallen out of use.

_If_ this is to be permitted, then can I suggest as alternative text:

    Furthermore, an identifier SHOULD refer to at most one resource over time; that is, IVORNs should not be reused for unrelated resources.  Note that a resource may potentially be dynamic (such as 'weather at telescope' or 'current version of the standard') -- here, there is a conceptually unique resource, even though the content of it may change in time.

Sentence 2 in this section does, I think, rule out a resource such as ivo://foo/version-of-the-server which might be different (is this right?) depending on which registry you resolved it from.  Is that what that sentence was getting at?

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK