This selector maps current specification to relevant requirements, according to the following semantic.

"Specification X is a description of the functional and/or technical solution that accomplishes the requirement Y"

Here the selection is multiple : An undetailed specification can realize a whole set of requirements. E.g., specifying existance of an authentication unit could induce following accomplishments :

1. user inditity requirement.
2. login/password authnetication.
3. roles abstraction definition.

Conversely, a set of detailed specification could be needed to describe a less detailed requirement.