Actual reduction to practice refers to the actual construction of the invention in physical form: in the case of a machine it includes the actual building of the machine, in the case of an article or composition it includes the actual making of the article or composition, in the case of a process it includes the actual carrying out of the steps of the process. Actual operation, demonstration, or testing for the intended use is also usually necessary. The filing of a regular application for a patent completely disclosing the invention is treated as equivalent to reduction to practice and is known as constructive reduction to practice.
Reduction to practice analyses have been largely rendered moot by thee American Inventors Act (AIA). Prior to the AIA, the inventor who proves to be the first to conceive an invention and the first to reduce it to practice will be held to be the prior inventor, but more complicated situations cannot be stated this simply. Thus, there are two (2) kinds of reduction to practice: Actual and constructive. Actual reduction to practice requires making a working model of the invention that demonstrates that the invention will work to fulfill its intended purpose.
Constructive reduction to practice is accomplished by the filing of a patent application with the USPTO that enables one of ordinary skill in the art to make and use the invention without undue research or experimentation.