_identifier is a container under information content entity for collecting types of terms to indicate a specific instance or clas of what was used or participated in an investigation. Identifiers are borne by a product or its packaging, and can be encoded in a variety of other information objects, such as bar codes, numerals, or patterns of dots.
Note: everybody agreed that identifier is probably a too general term. We however felt that it would be appropriate to group "identifiying" terms under some kind of umbrella. We therefore propose to use _identifier for that purpose. As per OBI conventions, the _ prefixing identifier indicates that this is a helper class and shouldn't be considered as final.