A resource analyzer selects a resource (e.g., document) from a grouping of resources. The grouping of resources can be any type of social tagging system used for information retrieval. The selected resource has an assigned uncontrolled tag and an assigned controlled tag. The controlled tag is a term derived from a controlled vocabulary of terms. Having selected the resource for analyzing, the resource analyzer identifies a first set of resources in the grouping of resources having also been assigned a same value as the uncontrolled tag as the selected resource. Similarly, the resource analyzer identifies a second set of resources in the grouping of resources having also been assigned a same value as the controlled tag. With this information, the resource analyzer then produces a comparison result indicative of a similarity between the first set of resources and the second set of resources.