I topic in which I think I already have the best solution (at the moment) but I would like to ask peer SEO members of WebmasterWorld.com for their opinion about the subject.
We have a PC domain and a Tablet/Mobile domain, they both will serve via dynamic serving under the same url. For the PC domain I have 1500 products <applicable to PC> to show to users but for the Tablet mobile I have approximately only 10% <applicable to tablet/mobile>to show to users. Between the two different type products only a small overlap of products appear. So for the one which have overlap we can use the rel=alternate tag.
And we have an extra complication factor - some of the mobile/tablet products can only be played for particular devices. So some can be played on a Iphone and not on an Android and the other way around.
So the big question is: what to do with the products which do not have an overlap. Because the algoritme doesn'thave a Mobile search funcationality and a PC search functionality.
My solution is based on Google's faulty redirects guidelines. Show the PC users if searching for a particular product (which is only in Tablet/Mobile version available) the Tablet/Mobile version url with a notification at the top for the users. Notification would state something like "This X product is only available for Table/Mobile and can not be played on a PC. If you want to only find PC products click here'.
This way the algoritme learns that this particular product isn't available in PC version. * Because it is given the Mobile/Tablet url with no rel=alternate in the source code. * We do not give a faulty redirects and eventually the page will not be shown any longer at the top of the SERP. * And finally we give the user the requested URL (with product) and also an alternative to search for products more suitable for its needs (the notification with the link to specific device products). So take user experience into account.
If a Mobile/Tablet search is done we do the same if the product is only available on PC.
And to overcome the problems that the Mobile/Tablet products are device specific we can show the Mobile/Tablet url but with the notification it is not available for Y device click here if you want to find only Y devices products.
Please let me know your pro's and con's on this problem and solution.
[edited by: aakk9999 at 8:40 am (utc) on May 14, 2014] [edit reason] Removed product niche, but clarified products difference [/edit]
I think that I would show all products (desktop or mobile) on the desktop site, but would make sure that products for mobile are in a different category. This is because I would personally often used desktop to search and review things that are for mobile only (just for example, lets say Apps) and later on go to mobile, access it from there and install it.
And to make sure users are not confused or frustrated, I would have it in separate categories (PC/desktop, Mobile). Where there is overlap, you would have 3 pages: desktop version of the page, desktop version of the page in Mobile category and Mobile version of the page. The canonical link element would point everywhere to a Desktop version of the page, where I would add a sentence with a link such as "Mobile version also available. More on mobile version or go to mobile page for download" or something to that extent.
This way you would also address products that do not overlap since your "Mobile only" product will show on Desktop version in the "Mobile" category, ready to be indexed by Google and the products that are available on both, desktop and mobile would have desktop page indexed, but there would be a sentence saying that there is a mobile version available, in case this is what the user searches for.