[OAI-implementers] handling unavailable data

[Ben Henley]

	I am currently implementing a simple OAI repository.
	I've looked through the specs but I can't find the answer to this
question:

	What is the recommended behaviour if data is temporarily
unavailable? 
	For example, suppose I have the information about supported metadata
formats stored in an SQL accessible database table. An OAI agent makes a
request to my repository but the database is unavailable for some reason.
	In the reference implementation I've looked at (the ASP one), a
partial answer could be returned. ie. <ListMetadataFormats>, <responseDate>
and <requestURL> elements would be sent but not <metadataFormat>. As I
understand http://www.openarchives.org/OAI/1.0/OAI_ListMetadataFormats.xsd,
the metadataFormat element is not compulsory (minOccurs=0).
	So a failure to retrieve any records could cause the repository to
lie by omission and say that it has no metadataFormats.
	Obviously the same could apply for other requests.	

	Is this a real problem? If data is not available, should a request
be ignored or is there a special message to return? Or is it assumed that
clients will revisit archives so rare failures like this will be forgotten?

	

Ben Henley <mailto:ben@biomedcentral.com>                    
Special Projects Editor
BioMed Central    
http://www.biomedcentral.com