OAI Harvesting Implementation Overview

I have been doing some work on the "Open Archives Initiative - Protocol for Metadata Harvesting".
From the servers point of view, it has the responsibility to respond to a number of requests - called verbs.

Verb	Description
Identify	Identifies a repository
ListMetadataFormats	Lists the formats that the repository provides; examples include Dublin Core and LOM
ListIdentifiers	This verb is an abbreviated form of ListRecords, retrieving only headers rather than records.
ListRecords	This verb is used to harvest records from a repository. Optional arguments permit selective harvesting of records based on set membership and/or datestamp
ListSets	This verb is used to retrieve the set structure of a repository, useful for selective harvesting.
GetRecord	Used to retrieve an individual metadata record from a repository.

The order of operation is usually the client coming along and making the following requests :

Request	Description
Identify	The client finds out the identify of the server.
ListMetadataFormat	The client finds out what formats are available.
ListRecords	The client gets a truncated list of records (say 10) and a resumption token.
GetRecord	For each of the records in the list obtained from the ListRecords request, the client makes a GetRecord request to get the contents.
Repeat last 2 steps	The client continues to ListRecords, passing in the resumption token, and gets the next list of 10 records; on each of which it does a GetRecord. This is repeated until the list is expired, at which point the server does not return a resumption token.