To illustrate this, suppose we want to eliminate the navigation bar from the page sidebar. We may create a rule in which the link density feature (is or has been ?) employed to distinguish such a part. However, when this rule (is or is being ?) applied to the page, all such elements are removed regardless of their locations, even if they are within the main content (e.g. Table of Contents).
When we want to say for example we may create or want to create X in which Y (is or has been or was) used for this purpose?
Example from web:
Peaceable school programs seek to create schools in which conflict resolution has been integrated at every level.