---
id: "composition"
type: "concept"
title: "Same-subject composition"
summary: "Multiple content instances can belong to one subject when composition is explicit."
problem: "Callers otherwise assume one row per subject."
why: "Subjects accumulate history and alternate content types."
mentalModel: "Subject → composed bag of content instances."
audiences: ["developers", "builders"]
prerequisites: ["raw-records"]
related: ["people-union"]
---
# Same-subject composition

Multiple content instances can belong to one subject when composition is explicit.

## Problem

Callers otherwise assume one row per subject.

## Why

Subjects accumulate history and alternate content types.

## Mental model

Subject → composed bag of content instances.