Generalization addresses the meaningful reduction of the map content during scale reduction. All geospatial data are generalized. Even the most detailed data represent only subsets of reality. Furthermore, data are further generalized for purposes of mapping, visualization, and efficient storage. A variety of generalization techniques have been developed to facilitate this process. All are scale dependent. Aggregation is one form of generalization that transforms large numbers of individual objects into summarized groups. This concept description is concerned with the nature of these procedures and their implications for professional practice. Generalization is an important part of cartography (and is therefore discussed conceptually in CV2 Data considerations), but is also a transformation common to many GIS procedures.