As a general rule, after the initial identification of subject-matter lacking unity, the claims and alternatives contained in claims are assigned to the identified groups of inventions. This step comprises the assessment of which of the remaining claims or alternatives in claims could potentially relate to the same technical problem. By doing so, groups of inventions are identified wherein each group of inventions relates to unitary subject-matter in view of the prior art at hand. If, in the course of grouping, the same special technical feature, which provides a contribution over the prior art, is identified in two groups of inventions, both groups of inventions need to be combined into one single group. Conversely, if, within one initial single group of inventions, claims or alternatives in claims are identified that are not linked by a potentially special technical feature, which provides a contribution over the prior art at hand, they will normally be separated into different groups of inventions. The initial grouping of claims and alternatives in claims into different inventions may require re-evaluation during the course of assessment of unity of invention.
Typically, different groups of inventions are based on different independent claims of the same category, on alternatives defined in one independent claim (see F-V, 3.2.1) or on dependent claims defining alternative embodiments, provided that the independent claim is either not novel or not inventive. However, different groups of inventions may also be based on independent claims in different categories if lack of unity is present between these claims.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/f_v_3_2.htm
Date retrieved: 17 May 2021