Abstract It is possible to be either vague or precise in the specification of an idea. For many purposes, loose characterizations can be perfectly adequate; the degree of specificity required depends upon the purpose of the characterization and the form of alternative interpretations. In attempting to retrieve information from memory, the specification of that information can be either vague or precise: just how specific the characterization can be depends upon how much is known of the information that is being sought; how specific the characterization must be depends upon what else within memory might be specified by a weaker characterization. In this paper we present a semiformal model of memory retrieval based upon the notion of variable levels of specification. We call the specification a description. A description of an entity is a collection of perspectives, each of which is a way of viewing that entity in terms of a previously known prototype. The level of specification of a description is provided both by the choice of prototype and by further specification of the ways in which the described entity differs from the prototype. We postulate that retrieval starts with a description of the desired information as an initial specification of the records sought from memory. This retrieval description guides the memory search process and helps determine the suitability of retrieved records for the purpose of the retrieval. The initial description can be modified as intermediate information becomes available during the retrieval cycle. Which records are retrieved is determined both by the form of the retrieval description and the form of encoding of these records at acquisition. The effectiveness of the descriptions for retrieval is determined by two properties, discriminability and constructability. Discriminability is the ability of a description to discriminate among all possible records in memory at the time of retrieval. Constructability is the likelihood that an appropriate description will be constructed at the time retrieval is desired.