Process Decomposition is a finite set of consistent and dependent activities that are organized into a hierarchy in which higher levels have greater authority, importance, and influence. At the upper level of the hierarchy there is the root process that consists of the activities and determines the course of action. All the activities are aligned with objectives of the process; they are performed one by one or in parallel.
Process decomposition also means a planning technique that allows defining process scope and time. This technique entails dividing a process into smaller, more manageable and predictable work elements (essentially activities, tasks and sub-tasks) until the process is defined at the lowest possible level. Work elements are scheduled, organized hierarchically, and performed under dependency rules. They form process scope and determine process duration.
The decomposition technique also considers such aspects as inputs (research data, materials, tools, etc.), resources (funds, labor, technology, etc.) and outputs (final product, service or other results). This technique allows determining how to best use available resources to transform inputs into outputs.