In 1981, the Federal Court of Appeal considered the question of the patentability of an invention that involved software in the case of Schlumberger.
[4] In Schlumberger, the applicant sought to patent a process for analysis of measurements from boreholes for oil and gas exploration.
[5] The court held, in the most often quoted passage of the decision,[3] that the calculations involved in the present invention would, if done by a man, be "mathematical formulae and a series of purely mental operations".
The Federal Court found that the "determination of subject matter must be based on a purposive construction of the patent claims.
On the other hand, it is also arguable that a purposive construction of the claims may lead to the conclusion that Schlumberger is distinguishable because a new one-click method of completing an online purchase is not the whole invention but only one of a number of essential elements in a novel combination.
The Patent Office published new guidelines for the determination of statutory subject matter based on a purposive construction of claims as guided in Amazon.com.
[15] The notice lays out a set of guidelines for claim construction in examination, relying on the Supreme Court decisions in the related cases of Free World Trust and Whirlpool.
"[17] The practice notice instead guides that the "evaluation of the subject-matter of a claim for compliance with section 2 of the Patent Act is to be made on the basis of the essential elements as determined through a purposive construction."