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Harvesting metadata with OAI-PMH


Again, the default application in the /alex/oai directory takes the value of the GET request as input and outputs a reply in the form of an XML stream.

All six of the protocol's verbs are enumerated and very briefly described below:


Identify - This verb is used to verify that a particular service is an OAI repository. The reply to an Identify command includes things like the name of the service, a URL where the services can be reached, the version number of the protocol the repository supports, and the email address to con- tact for more information. This is by far the easiest verb. Example:

http://www.infomotions.com/alex/oai/?verb=Identify [http://www.infomotions.com/alex/oai/?verb=Identify]


ListMetadataFormats - Meta data takes on many formats, and this command queries the repository for a list of meta data formats the repository supports. In order to be OAI compliant, a repository must at least support the Dublin Core. (For more information about the Dublin Core meta data format see http://dublin.or/ and http://www.iso.or/standards/resources/Z39-85.pdf.) Example:

http://www.infomotions.com/alex/oai/?verb=ListMetadataFormats [http://www.infomotions.com/alex/oai/?verb=ListMetadataFormats]


List sets - The data contained in a repository may not necessarily be homogeneous since it might contain information about more than one topic or saved in more than one format. Therefore the verb List sets is used to communicate a list of topic or collections of data in a repository. It is quite possible that a repository has no sets, and consequently a reply would be contain no set informa- tion. Example:

http://www.infomotions.com/alex/oai/?verb=ListSets [http://www.infomotions.com/alex/oai/?verb=ListSets]


ListIdentifiers - It is assumed each item in a repository is associated with some sort of unique key -- an identifier. This verb requests a lists of the identifiers from a repository. Since this list can be quite long, and since the information in a repository may or may not significantly change over time, this command can take a number optional qualifiers including a resumption token, date ranges, or set specifications. In short, this command asks a repository, "What items do you have?" Example:

http://www.infomotions.com/alex/oai/?verb=ListIdentifiers [http://www.infomotions.com/alex/oai/?verb=ListIdentifiers]


GetRecord - This verb provides the means of retrieving information about specific meta data re- cords given a specific identifier. It requires two qualifiers: 1) the name of an identifier, and 2) name of the meta data format the data is expected to be encoded in. The result will be a description of an item in the repository. Example:

ht- tp://www.infomotions.com/alex/oai/?verb=GetRecord&metadataPrefix=oai_dc&identifier=twain-n ew-36 [ h t t p : / / w w w . i n f o m o t i o n s . c o m / a l e x / o a i / ? v e r b = G e t R e c o r d & m e t a d a t a P r e f i x = o a i _ d c & i d e n t i f i e r = t w a n-new-36] i


ListRecords - This command is a more generalized version of GetRecord. It allows a service pro- vider to retrieve data from a repository without knowing specific identifiers. Instead this command allows the contents of a repository to be dumped en masse. This command can take a number of qualifiers too specifying data ranges or set specifications. This verb has one required qualifier, a meta data specification. Example:

h t t p : / / w w w . i n f o m o t i o n s . c o m / a l e x / o a i / ? v e r b = L i s t R e c o r d s & m e t a d a t a P r e f i x = o a i _ d c


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