Characteristic of an entity. An attribute can be inherent in an entity or externally imputed. The attributes of the entity serve as the means by which users formulate queries and interpret responses when seeking information about a particular entity. Attributes generally fall into two broad categories. There are, on the one hand, attributes that are inherent in an entity, and on the other, those that are externally imputed. The first category includes not only physical characteristics (e.g., the physical medium and dimensions of an object) but also features that might be characterized as labeling information (e.g., statements appearing on the title page, cover, or container). The second category includes assigned identifiers for an entity (e.g., a thematic catalogue number for a musical composition), and contextual information (e.g., the political context in which a work was conceived). Attributes inherent in an entity can usually be determined by examining the entity itself; those that are imputed often require reference to an external source.