[tdwg-guid] RE: tdwg-guid Digest, Vol 5, Issue 5

Jason Best jbest at brit.org
Tue Jun 5 02:58:39 CEST 2007

Thanks for all the responses and discussions. First I'll quickly answer
some questions, then ask some more. 

Richard, when I say "collection" I mean "collection event". I'll try to
be more precise in the future but, just as a warning, I'm bound to slip.

Someone said something about incorporating the accession number into the
LSID. You could do that, but it violates the "semantically opaque"
aspect of the LSID identifier.

Paul said:
"Anybody got any views (strong, otherwise or proxy for others views) on
whether the LSID should refer to data+metadata or just metadata?"

I think Roger's response covers the issue, but I'll add my perspective.
Ultimately, you need both (and this is my STRONG view). In our current
situation, we have no need to resolve an LSID to data, only metadata for
records that have no bytestream representation. That will change once we
implement LSIDs for our images, documents and GIS files.

Roger, I think your explanation is getting me closer to understanding
how we should implement this, but I think I'll have to delve into RDF a
bit more. Right now I'm thinking in database schemas and not RDF and I
think the schema we have will allow the scenario you describe but I'd
like to spell it out a little more just to make sure I understand it.
I'm assuming when you say a "thing that changes", that will have a
single LSID that does not change, but everything else about the "thing
that changes" will change based upon the current version. So this is
what I understand, in pseudo-RDF:
("Specimen_metadata" just represents the changing content, I just use
different numbers to indicate this.)

Specimen X Record
LSID: Specimen_X_LSID
versionedAs: Version_3_LSID
Specimen_metadata: [567]

Specimen X Version 1
LSID: Version_1_LSID
isReplacedBy: Version_2_LSID
Replaces: NULL
isVersionOf: Specimen_X_LSID
Specimen_metadata: [123]

Specimen X Version 2
LSID: Version_2_LSID
isReplacedBy: Version_3_LSID
Replaces: Version_1_LSID
isVersionOf: Specimen_X_LSID
Specimen_metadata: [345]

Specimen X Version 3
LSID: Version_3_LSID
isReplacedBy: NULL
Replaces: Version_2_LSID
isVersionOf: Specimen_X_LSID
Specimen_metadata: [567]

Your description of "versionedAs" in your email seems pretty clear, so
that is what I based the above on, but from the TDWG spec it is not so
clear to me if I got it right. From what you say, it sounds like
versionedAs would only point to one version of the metadata (the current
version) but the description below makes it sound like a way to access
older versions and would therefore have to be a listing of all the older
versions. Or, does versionedAs go in the non-current versions and point
to the unchanging LSID of the "thing that changes"?

"When the metadata linked to by this LSID is liable to change the LSID
authority may choose to make an older version of the metadata available
via another LSID. For some clients retrieving the version of the data
current at a particular time (rather than the current metadata) may be
important. By storing the value of the versionedAs LSID that is supplied
with the current metadata they can be sure that they will always be able
to refer to a particular version of the metadata. It is recommended that
the DublinCore term isVersionOf is used to point from the versioned
metadata to the principle LSID."

Thanks for all the help!


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