aggregations

Aggregation is the process of combining multiple elements into a single, higher-level entity. It is used across disciplines to create summaries, describe patterns over groups, or form composite objects from parts. Aggregations can be numerical, such as totals and averages, or structural, such as a collection of related objects that are treated as a whole.

In data processing and databases, aggregation refers to operations that summarize data values across a set of records. Common aggregate functions include sum, count, average, minimum and maximum. These operations are often performed with grouping, such as grouping by a category, and can be extended with rollup or cube for hierarchical summaries. Streaming and windowed aggregations compute summaries over moving subsets of data.

In economics and statistics, aggregate measures describe the overall state of a system, such as gross domestic product (GDP), total employment, or population averages. In ecology and biology, animal aggregation refers to the clustering of individuals in space or time for feeding, mating, or protection. Aggregation also appears in linguistics and data science, referring to the aggregation of signals, features, or populations.

In software design, aggregation denotes a whole-part relationship where a complex object is made up of components, but the components may outlast the whole. This is distinct from composition, where parts are owned and managed by the composite object. The term also appears in modeling and information systems to describe the creation of higher-level abstractions from lower-level data and components.