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.

The requirements of Art. 84 with regard to the characterisation of a product by parameters can be summarised as follows (see T 849/11):

the claims must be clear in themselves when read by the skilled person (not including knowledge derived from the description); 
the method for measuring a parameter (or at least a reference thereto) must appear completely in the claim itself; and 
an applicant who chooses to define the scope of the claim by parameters needs to ensure that the skilled person can easily and unambiguously verify whether they are working inside or outside the scope of the claim. 

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):

the measurement method to be employed belongs to the skilled person's common general knowledge, e.g. because there is only one method, or because a particular method is commonly used; or 
all the measurement methodologies known in the relevant technical field for determining this parameter yield the same result within the appropriate limit of measurement accuracy. 

For further issues relating to lack of support and sufficiency of disclosure regarding parameters, see F‑III, 11, and F‑IV, 6.4.

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