Linked Data and Semantic Web CoolURIs, 303 redirects and Page Rank.

I am attempting to understand how the the CoolURI 303 redirect pattern for
the semantic web (http://www.w3.org/TR/cooluris/) can be implemented
without negative impact on search engines.

This pattern appears to allow site content to be indexed, but prevents page
rank from flowing through internal links due to the use of a 303 redirect.

For example in Griffith's Research-Hub: http://research-hub.griffith.edu.au

A get request to the URI of Howard Wiseman:
http://research-hub.griffith.edu.au/individual/n33a4e2d3057476efaff5ce1884564a8f

Will resolve to different urls based on content negotiation.

For RDF:
wget --header "Accept: application/rdf+xml"
http://research-hub.griffith.edu.au/individual/n33a4e2d3057476efaff5ce1884564a8f

results in a "303 see other" redirect to the RDF version of the entity:
http://research-hub.griffith.edu.au/rdf/n33a4e2d3057476efaff5ce1884564a8f/n33a4e2d3057476efaff5ce1884564a8f.rdf

For HTML:
wget --header "Accept: text/html"
http://research-hub.griffith.edu.au/individual/n33a4e2d3057476efaff5ce1884564a8f
results in a "303 see other" redirect to the HTML version of the entity
(our old friend the "display" version:
http://research-hub.griffith.edu.au/display/n33a4e2d3057476efaff5ce1884564a8f

Note: There will never be a HTML page at
http://research-hub.griffith.edu.au/individual/n33a4e2d3057476efaff5ce1884564a8f
just
a HTTP response

Links will be presented as the "individual" uri and then redirect to the
"display" url.

All good so far - this is a perfectly functional example of the Cool URI
specification at work.  Unfortunately it results in a few issues in
practice.

If the links we present to the outside world for harvesting eg. via sparql
endpoint, OAI-PMH or open social widget etc is the canonical "individual"
URI, clients will be able to get to the "display" url, but the google page
rank that would normally flow from these external links will not.

The specification of a 303 redirect describes it as:
http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

> "The response to the request can be found under a different URI and SHOULD
> be retrieved using a GET method on that resource. This method exists
> primarily to allow the output of a POST-activated script to redirect the
> user agent to a selected resource. *The new URI is not a substitute
> reference for the originally requested resource*. The 303 response MUST
> NOT be cached, but the response to the second (redirected) request might be
> cacheable.
>


The different URI SHOULD be given by the Location field in the response.
> Unless the request method was HEAD, the entity of the response SHOULD
> contain a short hypertext note with a hyperlink to the new URI(s)."


Google correctly implements the specification and does not assign the page
rank of the "individual" URI to the "display" URL as it is "*not a
substitute reference for the originally requested resource".*

 The same is true of internal links, a high page rank home page will not
pass page rank on to "display" urls if the pathway to those urls is via
"individual" uri links.

I am not sure what the solution is here as it seems the realms of SEO and
the conventions of the web they are built on are not a good fit for
semantic web best practice.

The most minimal compromise I can think of is to move away from the use of
a 303 redirect to a redirect that conserves the flow of google page rank.

   - "302 Found" redirect is the recommended replacement for 303 for
   clients that do not support HTTP 1.1  and it does allow a certain amount of
   google page rank to flow.
   - "301 Moved Permanently" is a poor fit for the Cool URI pattern, but
   passes on the full page rank of the links.
   - rewriting all URIs the URL would also work, but would break the
   coolURI pattern.

The pragmatist in me feels that if we are going to make a change for the
purposes of SEO, it might as well be the one with best return, i.e. 301
redirect.

Note: Indexing is not the problem here, content is indexed.  The issue
relates to page rank not flowing through a 303 redirect.

I have tested and can confirm that 303 redirects are an issue for a number
of reasons:

   - page rank does not flow through a 303 redirect
   - page rank can not be assigned from a url to a uri with a rel=canonical
   tag if URI does a 303 redirect (preventing aggregation of pagerank from
   external links to URL)
   - URI and URL are indexed separately
   - rdfa schema.org representations of URIs do not translate to URL (ie.
   representation described at URL A, talking about URI B, does not get
   connected to representation described at URL B)
   - url parameters are not passed by a 303 redirect.
   - impact on functinality of google analytics tracking eg. traversing the
   site is seen as a series of direct page visits.

Essentially - as far as search engines are concerned - every URL and URI is
an island, with no connections between them.  At best a URL can express a
rel=canonical back to it's corresponding URI, no pagerank will flow through
links.

Any guidance you can provide would be appreciated.

-- 

o-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
| Mark Fallu
| Manager, Research Data (Acting)
| Office for Research
| Bray Centre (N54) 0.10E
| Griffith University, Nathan Campus
| Queensland 4111 AUSTRALIA
|
| E-mail: m.fallu@griffith.edu.au
| Mobile:  04177 69778
| Phone:  +61 (07) 373 52069
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