We are using canonical link tags for product pages in a scenario where the URLs on the site contain category names, and the canonical URL points to a URL which does not contain the category names.  So, the product page on the site is like www.example.com/clothes/skirts/skater-skirt-12345, and also like www.example.com/sale/clearance/skater-skirt-12345 in another category.  And on both of these pages, the canonical link tag references a 3rd URL like www.example.com/skater-skirt-12345.  This 3rd URL, used in the canonical link tag is a valid page, and displays the same content as the other two versions, but there are no actual links to this generic version anywhere on the site (nor external). Questions: 1. Does the generic URL referenced in the canonical link also need to be included as on-page links somewhere in the crawled navigation of the site, or is it okay to be just a valid URL not linked anywhere except for the canonical tags? 2. In our sitemap, is it okay to reference the non-canonical URLs, or does the sitemap have to reference only the canonical URL?  In our case, the sitemap points to yet a 3rd variation of the URL, like www.example.com/product.jsp?productID=12345.  This page retrieves the same content as the others, and includes a canonical link tag back to www.example.com/skater-skirt-12345.  Is this a valid approach, or should we revise the sitemap to point to either the category-specific links or the canonical links?