Glossary of Boundary and Decomposition Terms

This glossary is designed for quick recall during architecture reviews. The terms below are intentionally short, but each one reflects a decision pattern used throughout the guide.

Core Boundary Terms

• boundary: The line that separates responsibility, ownership, model meaning, and operational accountability.
• service boundary: A boundary made explicit through contracts, deployability, and ownership.
• bounded context: The space in which a domain model has one intended meaning and stays internally consistent.
• business capability: A stable statement of what the organization must be able to do, such as billing or fulfillment.
• value stream: The end-to-end flow of work that delivers value and reveals workflow handoffs.

Design Quality Terms

• cohesion: How strongly the concerns inside a boundary belong together.
• coupling: How strongly one boundary depends on another for routine behavior.
• boundary tension: The pressure showing that a boundary is too mixed internally or too coordinated externally.
• chatty interaction: A pattern of excessive small calls between services, usually signaling weak contract or boundary design.
• distributed monolith: A system whose parts are separately deployed but still tightly coupled in release, data, and behavior.

Data and Workflow Terms

• authoritative data: The source of truth for a business record or invariant.
• read model: A derived projection optimized for queries or reporting.
• eventual consistency: A model where related updates converge over time rather than instantly everywhere.
• saga: A coordinated multi-step workflow across boundaries with explicit handling for partial failure.
• compensation: A business action that restores an acceptable state after part of a distributed workflow succeeds and another part fails.

Team and Platform Terms

• stream-aligned team: A team aligned to an area of business flow or product value.
• platform team: A team that provides common capabilities and paved-road tooling for delivery and operations.
• enabling team: A team that helps others adopt practices, patterns, or capabilities without permanently owning their domain.
• service catalog: A structured inventory of service ownership, metadata, dependencies, and operational links.

Migration Terms

• strangler pattern: A migration pattern in which a new boundary gradually takes over behavior behind a stable facade or routing layer.
• anti-corruption layer: A translation boundary that protects one model from another model’s meanings and constraints.
• transitional architecture: A temporary coexistence state during migration that should be explicit and time-bounded.

Architecture Styles

• monolith: A single deployable unit that may still contain internal modules or strong boundaries.
• modular monolith: A monolith with explicit internal boundaries, dependency rules, and ownership discipline.
• microservices: A distributed architecture built from independently evolvable service boundaries, each with real operational cost.

Use this glossary as a reset tool. If a service debate becomes vague, return to the terms and check whether the participants are using the same meanings.