8.7.3.12 Relative Terms

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A specification may describe an invention by way of relative terms.  This does not usually present a problem with the construction of the specification, provided the skilled addressee can determine what is encompassed by the claims.

In particular, a specification does not lack full description merely because some experimentation of a routine nature is necessary to perform the invention. In Poseidon Industri A.B. v Cerosa Limited (1982) FSR 209, the patent related to a diving suit with a "close fit", such that only a "minimum air layer" could form between the suit and the diver's body. It was held that the patent was not bad for insufficiency, even though the specification made use of a relative term which did not describe how much room there should be between the diver and the suit. In this case, "a little ordinary trial and error" would be sufficient to ascertain the satisfactory minimum layer of air.

See also Catnic Components Limited v Hill & Smith Limited (1982) RPC 183.