Hi Eric!

This is a good article!

You seem to have some confusion about recordPacking.  In the fragment below,
you twice seem to be saying that the alternative to XML for a record
response is plain text.  That's not true.

> The results of searchRetrieve operations can be returned
> in any number of formats, as specified via explain
> operations. Examples might include structured but plain
> text streams or data marked up in XML vocabularies such
> as Dublin Core, MARCXML, MODS, etc. Below is a simple
> request for documents matching the free text query "dogs":
>
>  http://example.org/?operation=searchRetrieve&query=dog&version=1.1
>
> In this case, the server returns three (3) hits and by
> default includes Dublin Core title and identifier elements.
> Each record is packaged in XML as opposed to formatted
> plain text:

Records are always returned as XML.  RecordPacking specifies whether that
XML can be embedded directly into the response or if it should be rendered
into a single string and then embedded.  The rendering simply turns '<' and
'&' into HTML entities of some kind.  This renders the XML record invisible
to the XML parser that is handling the response.  Subsequent processing can
turn the entities back into characters and the XML record can then be turned
over to an XML parser.  This string representation can save considerable
wasted parsing during the message processing.

It would seem that string encoding would be the clear choice for all
responses; so why the XML recordPacking option?  For those of us writing
thin clients in SRU, we use XSL stylesheets to render the response.  The
string encoded records look like a single atom to XSL and can't be easily
rendered.  So we asked for the records to be directly embedded; hence the
XML recordPacking.

Hope this helps!

Ralph

> -----Original Message-----
> From: Eric Lease Morgan [mailto:[log in to unmask]]
> Sent: Sunday, July 04, 2004 3:54 PM
> To: [log in to unmask]
> Subject: introduction to sru
>
> I have completed my first draft of an article entitled "An introduction
> to Search/Retrieve URL Service (SRU)". From the text:
>
>    This article is an introduction to the "brother and sister" Web
>    Service protocols named Search/Retrieve Web Service (SRW) and
>    Search/Retrieve URL Service (SRU) with an emphasis on the later.
>    More specifically, the article outlines the problems SRW/U are
>    intended to solve, the similarities and differences between SRW
>    and SRU, the complimentary nature of the protocols with OAI-PMH,
>    and how SRU is being employed in a sponsored NSF grant called
>    OCKHAM to facilitate an alerting service. The article is seasoned
>    with a bit of XML and Perl code to illustrate the points.
>
>    http://dewey.library.nd.edu/morgan/sru/intro2sru.txt
>
> Comments and corrections are more than welcome.
>
> --
> Eric "Getting Pyched For Fireworks" Morgan
> (574) 631-8604