Claiming Claims

So, a patent does not give you a right to use your own invention.  Actually, this is not strictly true in all cases, and this is partly due to the manner in which patent systems handle exclusivity.  The modern patent system use "claims" to demarcate the border of exclusivity.  A claim is basically a single sentence that is meant to encapsulate the concept of the invention in a format that can be compared against the infringing product or method.  This is a straight pattern-matching exercise (with a penumbra of fuzziness introduced by something called the Doctrine of Equivalents).  

Patent practitioners, early on, introduced some very basic concepts from logic and set theory into claim interpretation.  Most claims, in particular in the non-chemical arts, use "comprising" in the preamble, which means that the elements recited in the claim are a minimally necessary and sufficient condition for infringement.  In the chemical arts, one will often see a more restrictive preamble, variants off of "consisting", which imply that the elements represent a complete set.  Add more, and there is no infringement (well, depending on how significant the thing you added).  What is interesting is a typical chemical patent claim can afford the patentee what is effectively exclusive use of their invention, in a way that no typical software or hardware patent claim can.  And issues of claim ambiguity are exacerbated in the non-chemical arts where the definition of claim elements is not tied to well-accepted scientific categorizations.  One must wonder whether these differences underlie the perceived split between the industries on issues of patent reform.