Where the invention relates to a product, it may be defined in a claim in various ways, viz. as a chemical product by its chemical formula, as a product of a process (if no clearer definition is possible; see also F‑IV, 4.12) or, exceptionally, by its parameters.
Parameters are characteristic values, which may be values of directly measurable properties (e.g. the melting point of a substance, the flexural strength of a steel, the resistance of an electrical conductor) or may be defined as more or less complicated mathematical combinations of several variables in the form of formulae.
The characteristics of a product may be specified by parameters related to the physical structure of the product, provided that those parameters can be clearly and reliably determined by objective procedures which are usual in the art. Where the characteristics of the product are defined by a mathematical relation between parameters, each parameter needs to be clearly and reliably determined.
The same applies to process-related features defined by parameters.
If the description of the method for measuring a parameter is so long that its inclusion makes the claim unclear through lack of conciseness or difficult to understand, the requirement under point (ii) can be met by including in the claim a reference to the description, in accordance with Rule 43(6).
Furthermore the requirement under point (ii) can still be met if it can be convincingly shown that (see T 849/11):
Characterisation of a product mainly by its parameters is only allowed in those cases where the invention cannot be adequately defined in any other way, provided that those parameters can be clearly and reliably determined either by indications in the description or by objective procedures which are usual in the art (see T 94/82). The same applies to a process-related feature which is defined by parameters.