This is the archive of the goodrelations dicussion list

Dear all:

Some shop applications, unfortunately, display the very same item at  
multiple URIs. This is problematic for Search Engine Optimization  
(SEO) and the Web of Data alike.

Examples and Causes
===================

There are two typical causes:

a) The navigation path of the shop system is used to create "clean"  
URIs:

   http://www.myshop.com/staplers/green_pocket_stapler123
   http://www.myshop.com/featured-items/green_pocket_stapler123

b) Parameters, e.g. such to control the language of the output, the  
preferred currency, the session ID (bad...), or the referrer.
This case is more severe, because it can easily cause 10 - 100  
duplicates per single page:

   http://www.myshop.com/staplers/green_pocket_stapler123
   http://www.myshop.com/staplers/green_pocket_stapler123?lang=en
   http://www.myshop.com/staplers/green_pocket_stapler123?currency=usd? 
lang=en
   http://www.myshop.com/staplers/green_pocket_stapler123?referrer=clicksale


Problems
========
1. If you embed GoodRelations data markup in RDFa syntax to your HTML/ 
XHTML shop templates, this may cause a massive duplication of data  
elements for applications that are trying to consume our shop data.
2. This will reduce the findability of your items in GoodRelations- 
aware applications.
3. It spoils the Web of Data ("proliferation of URIs").
4. Your pages will receive a lower ranking in search engines, because  
the amount of links will be spread over multiple URIs.
5. Pages may even be banned from search engines ("duplication of  
content"); that is independent of whether you are using GoodRelations  
or not.
6. Crawlers will waste more resources crawling your site, consume more  
of your valuable bandwidth, and are more likely to use outdated cached  
versions of your pages.

Solutions
=========
1. The ideal solution is to aim for canonical URIs (one URI per  
product) as much as possible. This may not be easy for pattern a), but  
it is straightforward for case b), e.g. by using session cookies and /  
or HTTP redirects.

2. If that is not possible, you should use *absolute* instead of  
*relative* identifiers in RDFa for all major data elements ("about"  
attribute in RDFa).

For example, in the template for the "product item" page, use

  <div about="http://www.myshop.com/staplers/green_pocket_stapler123#offering 
" typeof="gr:Offering">
  ...

instead of

  <div about="#offering" typeof="gr:Offering">
  ...

The effect will be that no matter from which URI the page was actually  
requested, the same RDF data will be extracted. It requires, though,  
that you can determine the canonical URI of the page at the time of  
the request.

3. The last option (but the least powerful, yet still much better than  
doing nothing) is to add owl:sameAs statements from the RDFa pattern  
to the canonical URI.
The canonical URI should also be used for the foaf:page property,  
which is the crucial link from the data to the page from where the  
product can be ordered.

Example:

   <div about="#offering" typeof="gr:Offering">
     <div rel="owl:sameAs" resource="http://www.myshop.com/staplers/green_pocket_stapler123#offering 
"></div>
     <div property="rdfs:label" content="Cool green stapler for $8.99"  
xml:lang="en"></div>
...
     <div rel="foaf:page" resource="http://www.myshop.com/staplers/green_pocket_stapler123 
"></div>
   </div>
</div>

Best wishes

Martin Hepp




--------------------------------------------------------
martin hepp
e-business & web science research group
universitaet der bundeswehr muenchen

e-mail:  hepp at ebusiness-unibw.org
phone:   +49-(0)89-6004-4217
fax:     +49-(0)89-6004-4620
www:     http://www.unibw.de/ebusiness/ (group)
          http://www.heppnetz.de/ (personal)
skype:   mfhepp
twitter: mfhepp

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