Aggregation

Aggregation is the process of combining multiple elements into a single whole. The concept is used across disciplines to simplify analysis, model complex systems, or describe how parts relate to a larger structure. Distinctions are made between aggregation, collection, and clustering, with aggregation typically focusing on producing a summary or composite object.

In data analysis and databases, aggregation refers to summarizing data across dimensions. Common operations include sum, average, count, minimum, and maximum. Aggregation is central to group-by queries and to the construction of reports and dashboards. Techniques such as roll-up and cube enable multi-level or hierarchical aggregations.

In computing and software design, aggregation describes a "has-a" relationship where one object contains another as part of its state, but without implying exclusive ownership. It contrasts with composition, where the contained objects' lifecycles are tied to the container. Aggregation is also used in distributed systems and streaming to combine partial results from multiple sources into a single view.

In biology and ecology, aggregation refers to a gathering of individuals, such as a swarm or flock, often for social interaction, foraging, or defense. In chemistry and physics, aggregation describes the clustering of particles, molecules, or colloidal entities due to intermolecular forces, affecting properties like solubility and reactivity.