Suppose A company, say ABC makes a product - a shelf that detects the item taken from it, along with the person who did, using image processing. The same company makes a product that does checkout automatically from the above data. And a retailer UVW buys the two products and integrates into his shop.
Will company ABC be sued? Or will the retailer get sued?
This has no yes or no answer. It depends on the patents claims.
To stay with your example of the operating system. I'll formulate some claims like you may find them in a patent concerning this invention.
An operating system.
Speech recognition.
Software taking input from speech and outputting access to an operatings service functions.
A system comprising and operating system, speech recognition and software configured to access features of the operating system through the recognized speech.
A good patent attorney will try going for all of those. Number 1 is, of course, not patentable anymore. Number 2 neither. But 3 and 4 might get through.
In this case, anyone selling software that accesses the os functions by speech could get sued from claim 3 directly and from claim 4 the moment this software gets combined with an operating system And as the software does nothing else, it would be directed at infringing a patent and the seller/produces could get sued too.
On the other hand, the claims might be something like
- The combination of an os with integrated speech recognition and direct access to features.
No good patent attorney should make a mistake like that [citation needed].
This claim allows you to sell software accessing the os through speech, as you are not fulfilling all limitations of the claim.
To come back to your example, it depends on the exact wording of the claims. Keep in mind that the person formulating those is trying to cover alternatives like the one you describe, so if you look closely, you will probably find that the software does literally infringe the patent. Sometimes claims will say something like "software configured to do this or that" in which case you dn't even have to do it, it just has to be a pssible function of the software.
If yes, what if two separate companies makes the above product - ABC makes the shelf and XYZ makes the checkout system. Would that be patent infringement?
In most cases, yes. Who infringes depends on the wording. If the claim is to software configured to etc then XYZ will probalby infringe the patent. If the claim covers a system with shelf and software, if XYZ sells the software only for that use, that can get them sued too, if this is not the main function, the retailer is the one that can get sued as e combines two not infringing products into one infringing product.
(Edit: I just checked status of Amazon Go Patent : Appl No : 13928345 - Final Rejection Mailed Appl No : 14495818 - Non Final Action Mailed )
Sorry, this means nothing. As long as it hasn't been abandoned, they can still file an RCE (Request for continuued examination) or an appeal and go on with examination.