The facts as we know them:
A list of available SRU servers is maintained by OCLC.
It is very easy to write basic SRU implementations. SOAP toolkits can use a WSDL description to generate protocol code. Then all we have to
do is implement the single client or server SRU method, which translates your query format into an CQL query (client) or a CLQ query into your database query (server).
CQL allows you to specify the format of the result set (Dublin Core, MARCXML, etc.). All servers must support Dublin Core and the SRUDiagnostics format.
The query can be a list of attribute-value pairs, or a chunk of XML.
CQL makes a distinction between string search (exact match of a string) and keyword search (finding all words of a string somewhere in the document).
Bibliographic searching is currently at the proposal stage.
The result set can contain state-preserving information, like the original query or an IP address, for use with lightweight clients.
Records in the result set are encoded as strings, with angle brackets escaped. This doesn't work very well for completely browser-based
clients using SRU, since you lose the ability to apply XPath statements to returned records. This problem will be addressed in a
Servers can/should retain result sets, so they can be referenced later, especially when the client is asking for multiple pages from a
set. A good way to force the server to keep a result set is to "touch" it with the client, and refresh the time.
Authentication/encryption is not built into the protocol, and must be addressed at a higher level. (See general web services literature.)
Contacts: Ralph LeVan (email@example.com), Matthew Dovey
Comparison to other systems: