The scope of many prior-art searches, including the validity search is determined by the selected claims of an issued patent, in target. The subject features of a validity search are the embodiments of an invention as claimed in the granted patent. Thus, the most important consideration during a validity search is claim interpretation.
Patent claims are basically of two kinds: independent claims and dependent claims. Independent claims are those that do not refer to another, preceding claim. Dependent claims incorporate by reference each and every limitation of each of the claims from which they depend.
Many patents include long chains or series of dependent claims, each referring to and incorporating the limitations of a preceding claim. Each dependent claim is narrower (i.e., more limited in scope) than the claim from which it depends.
Essentially, patent claims are composed of limitations, phrases that identify and describe, or limit, the various components (or steps, in the case of a method or process claim) of the claimed invention. The various words and phrases that appear in the patent claims are to be interpreted or construed according to their normal or accustomed meaning. If no such accepted definition exists, then most likely the patent attorney may have created or coined new words or phrases, or has used words or phrases in an unconventional manner (as some of the patent office allow the patent applicant to be his/her own lexicographer; that is, he/she can create and define the meanings of the words used in his application).
Further, in some cases, the patent specification is used as a guide to claim interpretation. If no clear definition is provided in the patent specification, the record of the prosecution of the patent application (known as the file wrapper and available from the Patent Office) should be studied to find meaning of the concerned terms.