It is the claims that define the boundaries of the patent owner’s rights. Don’t fall into the trap of concluding that the title or the abstract or the general description found in the text of the patent indicates what is patented. For example, United States Patent No. 6 074 877 is titled “Process for transforming monocotyledonous plants”. From the title, it sounds like these patent owners have protected a transformation process(es) for transforming all monocot plants. Examination of the claims shows, however, that only transformation of cereal plants is protected, and furthermore that to be covered, the method must involve wounding an embryogenic callus or treating an embryogenic callus with an enzyme that degrades cell walls prior to transferring DNA into the cells with Agrobacterium. A bit different than what the title implied.
To determine if someone is infringing a patent, that is making, using, etc., without the patent owner’s permission, the allegedly infringing product is compared only to the claims. The scope of the claimed invention may not always be clear however, from reading the plain language of the claim, despite the requirement that claims must be stated definitively so that others are able to understand what is and what is not protected. In the case above, for example, several terms in the claims (e.g., “cereal plants”, “embryogenic callus”, and ” enzyme that degrades cell walls”) might not be clear. Thus, claim interpretation can be difficult; a proper analysis is done by reading the claims in the context of the specification and in the context of the “prosecution history” (the back and forth negotiations of the claim language between the patent applicant and the patent office).
Claims come in two flavours: independent and dependent. An independent claim stands alone. It includes all the necessary limitations and does not depend on or include limitations from any other claim. A dependent claim refers back to and further limits another claim or claims. Moreover, a dependent claim includes all the limitations of the claim incorporated by reference.