invention? Utility For a product to have utility it must perform some useful function. The requirement for utility originates from the definition of invention as a "new and useful art" The requirement is generally easy to meet, however, it does limit the scope of protection by excluding methods that would not be useful. Subject matter In addition to the three criteria above, in order to be patentable the invention must also be: a product (e.g., a door lock) a composition (e.g., a chemical composition used in lubricants for door locks) a machine (e.g., a machine for making door locks) a process (e.g., a method for making door locks) an improvement on any of the above As such, there are number of matters that cannot be patented. Among such matters include certain new plant matters, and medical treatments within the body (diagnoses based on, for example, blood tests, are patentable). Some types of computer programs are also not patentable by law, as computer code by itself is not something physical. However, according to the Canadian Intellectual Property Office, a computer program may be patentable if it offers a new and inventive solution to a problem by modifying how the computer works. Some things that cannot be patented include: "disembodied ideas, concepts or discoveries" "scientific principles and abstract theorems" "methods of medical treatment or surgery" "higher life forms" "forms of energy" "features of solely intellectual or aesthetic significance" "printed matter" The list of prohibited matters notably differs from the United States. With respect to patents for software, while mere algorithms are not patentable per se (mere algorithms may be protected by Canadian copyright law), software may be protected by Canadian patent law if it meets the traditional criteria for patentability (that is, it must be new, non-obvious and useful). In other words, if for example the software is new and non-obvious, it would be patentable in Canada if the software directly provided a functional real world useful result (and not merely the calculation of a mere algorithm). Filing a patent For patent applications filed in Canada prior to 1 October 1989, a patent would expire 17 years after it was issued. For those filed on or after 1 October 1989, a patent would last to a maximum of 20 years after the patent application was filed. In Canada, all patent applications (unless they are withdrawn by the applicant) are made public 18