EML versioning

[David Blankman]

Hi David,

I've got a quick question on EML document versions. Should all versions of a 
document be available (like cvs) or only the latest one?

-- Sven Bohm (KF8A)



Sven,

There is no simple answer to that question. In order for you to get a 
broader perspective, I am copying the metacat and eml lists and the IM 
list. My aplogies to those of you who may get multiple copies.

I am answering your question from several points of view. Hopefully one 
of the answers is the one to the question you actually are asking.

Here is the way metacat handles versioning (this is a simplified 
explanation as there are other tables involved):

   1. Say there is an eml document in metacat with docid kbs.1.1
   2. You make some changes and decide to insert kbs.1.2
   3. Metacat deletes the references to kbs.1.1 from the active table
      XML_DOCUMENTS and then does an insert into the XML_REVISIONS table.
   4.  kbs.1.2 is then placed into the XML_DOCUMENTS table.

There are no public tools that are designed to query the XML_REVISIONS 
table, so for all practical purposes, the older documents are inaccessible.

 From an archival perspective, the question you ask is similar to the 
question: how much rollback capability to you have/want/need in your 
source database.

The more dynamic your metadata, the trickier the versioning issue is. 
Since you are generating eml dynamicly, the issue of versioning is 
important, as I see it, only in a metacat sense. If your eml is 
harvested, then the docid of scope.identifier.version in the 
"harvestDocument.xml" determines whether there is a new harvest or not. 
If your docid says kbs.1.1 and kbs.1.1 is already in the metacat, then 
there will be no new harvest even if the content of kbs.1.1 has changed.

The other question is -- when does dynamicly generated eml become a new 
version.  If you have remote sensing data with daily or hourly updates, 
and your temporal coverage is generated by querying a data column in a 
data table, then from one point of view, you have a new version daily or 
hourly. When Barbara Benson and I discussed this issue, she decided that 
they might generate a "new version" quarterly or semi-annually or in 
some cases annually depending on the kind of data.

Let me know if the question you were trying to ask was different from 
any of the ones that I answered.

David




bohms at msu.edu wrote:

>Hi David,
>
>I've got a quick question on EML document versions. Should all versions of a 
>document be available (like cvs) or only the latest one?
>
>-- Sven Bohm (KF8A)
>
>  
>

-- 
David E. Blankman
EML Integration Developer
Long Term Ecological Research Network Office
University of New Mexico
801 University, SE #104
Albuquerque, NM 87106
(505) 272-7346 / (505) 272-7080 FAX

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