xISBN and REST

Looking at the xISBN service docs tonight while running Pleiades data import tests, I see that there is support for "REST-ful" short URLs in version 1 and cool URIs in version 2. That seems pretty cool to me, so let's try one out:

sean@lenny:~$ curl -v http://xisbn.worldcat.org/webservices/xid/isbn/0596002815
> GET /webservices/xid/isbn/0596002815 HTTP/1.1
> Host: xisbn.worldcat.org
> Accept: */*
>
< HTTP/1.1 200 OK
< Server: Apache-Coyote/1.1
< Content-Type: text/xml;charset=UTF-8
< Content-Length: 305
< Date: Wed, 28 May 2008 06:04:12 GMT
<
<?xml version="1.0" encoding="UTF-8"?>
<rsp xmlns="http://worldcat.org/xid/isbn/" stat="ok">
<isbn    >0596002815</isbn>
<isbn    >1565928938</isbn>
<isbn    >1565924649</isbn>
<isbn    >0596513984</isbn>
<isbn    >2841770893</isbn>
<isbn    >1600330215</isbn>
<isbn    >8371975961</isbn>
</rsp>

Looks good (links would be even better), but that "stat" attribute on the rsp element smells a little fishy ... let's try a bogus ISBN:

sean@lenny:~$ curl -v http://xisbn.worldcat.org/webservices/xid/isbn/05960bogus
> GET /webservices/xid/isbn/05960bogus HTTP/1.1
> Host: xisbn.worldcat.org
> Accept: */*
>
< HTTP/1.1 200 OK
< Server: Apache-Coyote/1.1
< Content-Type: text/xml;charset=UTF-8
< Content-Length: 103
< Date: Wed, 28 May 2008 06:13:38 GMT
<
<?xml version="1.0" encoding="UTF-8" ?>
<rsp xmlns="http://worldcat.org/xid/isbn/" stat="invalidId"/>

The response has a status code 200, which should mean success, but there's an error code specific to xISBN in the representation: "invalidID". The underlying RPC nature of xISBN leaks through the cool URI abstraction in this situation. That request has to result in a 404 ("Not Found") if xISBN is going to be RESTful, right?

Speaking of curl, Mark Nottingham points out a potential pitfall and collects a bunch of useful comments here.