Inconsistency between full searchable registries

[Menelaus Perdikeas]

Hi Thomas, 

Indeed, as I've explained we were black-listed in HEASARC for performing too many queries. Tom McGlynn however managed to get the block lifted and I see that we've now successfully harvested HEASARC resources. 
HEASARC aside, and as regards the other missing resources I would really have to investigate on a case by case basis but in general what Theresa explained (about resources falling through the cracks in incremental harvests) is a plausible explanation. If a registry updates / deletes or creates a new resource and does not accurately reflect the time-stamp in the OAI-PMH envelope, then records will be missed in incremental harvests and will only be fetched when a full harvest occurs (in the case of Euro-VO once a month). 

I think that race conditions are also possible in the design of the OAI-PMH protocol itself (but these can be addressed for practical purposes by using comfortable overlaps in incremental harvests). 

There's a report we produce that identifies mismatches (broken down per managed authority) between any two registries and indeed discrepancies of all kinds do exist. I guess that as long as they are kept to a reasonable minimum and only for "recently changed" resources and as long as the different registries eventually converge, it shouldn't matter too much. 

Cheers, 
Menelaus. 


From: "Thomas Boch" <thomas.boch at astro.unistra.fr> 
To: registry at ivoa.net 
Cc: ops at ivoa.net 
Sent: Monday, March 14, 2016 3:43:45 PM 
Subject: Inconsistency between full searchable registries 

Hi Registry-enthusiasts, 

I would like to report on an inconsistency I found between resources available in the EuroVO registry and in the VAO/STScI registry. 

I am performing daily a full harvesting (through OAI PMH) of the registry in order to retrieve and filter out services of interest to Aladin Desktop. I used to query the STScI registry for this task until I found out some active resources were missing (for instance ivo://cfa.tdc/hectospec/hectospec_public.ssap.q/ssa ). I then switched to the EuroVO registry and just found out that some other resources, for instance ivo://nasa.heasarc/skyview/skyview , were also missing (but available in the STScI registry). 

The full list of missing resources for each registry is attached to this message. From a quick look: 

- STScI registry is mostly missing 1300 VizieR resources 

- EuroVO registry is mostly missing HEASARC services. Menelaus confirmed me that they had an issue with querying the HEASARC registry. 


What should I do ? I am not really keen on querying the two registries and merging the results, as I feel this should not be done at my side. I would expect consistency between full registries, at least for resources older than 1 week. Am I missing something ? 


Cheers, 

Thomas 


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