Once an invention is patented in Canada, exclusive rights are granted to the patent holder as defined by s.42 of the Patent Act (R.S.C., 1985, c. P-4). Any interference with the patent holder's "full enjoyment of the monopoly granted by the patent" is considered a patent infringement. Making, constructing, using, or selling a patented invention without the patent holder's permission can constitute infringement. Possession of a patented object, use of a patented object in a process, and inducement or procurement of an infringement may also, in some cases, count as infringement. Canadian Statute In Canada, patents are governed by the Patent Act. Section 42 of the Patent Act establishes the rights of a patent holder: By granting the patent holder the exclusive right, privilege and liberty of making, constructing, using, and selling the invention, the patent act establishes that any other person making, constructing, using, or selling the patented invention is infringing that patent. Whether there has been an infringement of a patent is usually a question of fact. The Patent Act is a federal statute and thus bilingual. Under the Constitution Act, 1982, both the English and French versions of the statute hold equal status before the courts. The terms "making, constructing, using, and selling" should be read in the context of their French counterparts, "fabriquer, construire, exploiter et vendre". This has affected the interpretation of the term "use" in cases involving patent infringement. Making, constructing, and selling Before an infringement can be established, it is necessary to construct the claims to determine what elements of the invention are essential and which are non-essential. Once the essential elements are established, making, constructing or selling something that copies the essential elements will be considered infringing. Purposive construction of claims Canadian patents should be given a purposive construction. The words used by the inventor are read in a manner consistent with what it is presumed the inventor intended; the interpretation should be sympathetic to the express or implicit purpose of the patent. The inventor's intent must be based on the patent, the court is not allowed to use extrinsic evidence of the inventor's intent. Courts should not take a purely literal interpretation of the patent, courts should determine whether a Person Skilled in the Art would conclude that strict adherence was essential or that a substitute or slight variation would not affect the invention. A person skilled in the art is