Bounded Context – tdonker.nl

Great quotes for the concept of Bounded Context

The mission of this overview is to compile great quotes that embody the essence of Bounded Context, facilitating a deeper comprehension of this fundamental DDD concept. Also examples as found in the DDD-literature are provided here. Bounded context and the ubiquitous language are the foundation of DDD.

An operational definition of where a particular model is well-defined and applicable. Typically a sub-system, or the work owned by a particular team.

The delimited applicability of a particular model. BOUNDING CONTEXTS gives team members a clear and shared understanding of what has to be consistent and what can develop independently. Evans 2003

updated: 09.05.2024

Patterns, Principles and Practices of Domain-Driven Design by Scott Millet and Nick Tune 2015

p54: Bounded contexts are used to form a protective boundary around models that helps to prevent software from evolving into a BBoM.
p86: Figure 6-10: depicts the Shipping Subdomain containing two bounded contexts: Booking Bounded Context and Pricing Bounded Context. So a subdomain can consists of multiple Bounded Contexts!
p88: Figure 6-12: depicts the Shipping Subdomain containing two bounded contexts: Basket Bounded Context and Pricing Bounded Context. So a subdomain can consists of multiple Bounded Contexts!
p119: A bounded context is defined based on team’s language, and physical artifacts.
p126: Treat bounded contexts like the borders of a country. Nothing should pass into the bounded context unless it goes through the border control and is valid. Just like countries where people speak a different language, so does the code within your bounded context.
p128: There are two aspects of a problem domain that you can use as a guide to identifying bounded contexts — terminology and business capabilities.
p129: A single team should be responsible for a bounded context, whether that crosses one or many applications or departments. So structure teams around bounded contexts; form product and services groups rather than trying to mirror the departmental structure of the business. Ensure that teams are responsible for a bounded context from presentation through domain logic and to persistence.
p131: Unlike a subdomain, a bounded context is a concrete technical implementation that enforces boundaries between models within an application. Bounded contexts exist in the solution space and are represented as explicit domain models in a context.
p136: There are no rules for defining the boundaries of a model and therefore bounded contexts. Instead you should base bounded contexts around linguistic boundaries, team organization, subdomains and physical deployments.
p157: Ideally a bounded context should have its own database.
p157: Applications can be composed of more than one bounded context.
p157: However, some people believe that the boundary of a bounded context should extend to the presentation layer. Udi Dahan’s business component gives the bounded context the responsibility for owning specific regions of the user interface.
p175: However, if your business is not complex or isn’t changing frequently then don’t automatically reach for the DDD hammer: remember there are other better suited tools in your development tool kit. Only focus your modeling efforts and DDD on the most complex bounded contexts that bring the most value to your customer.
p221: Inside a bounded context you may have a number of responsibilities. In a Shipping bounded context, for example, there may be logic to deal with priority orders and standard orders. By isolating each major responsibility as a component, you’ll find yourself having clearer conversations with the business and all the other benefits of DDD that you’ve already seen arise from making the implicit explicit.
p271: Business Components Need Their Own APIs. If you work to the principle that each business component has its own private database, the only sensible way to share data with a web application is for each business component to have its own set of APIs exposing that data.
p263: Storage Is Cheap—Keep a Local Copy – An option that many teams take in this situation to reduce unwanted coupling is to store all the data each bounded context needs locally.
p293: Dogfooding Your APIs – When all your communication is over HTTP, there may be no need to have dedicated channels for internal and external communication. In plain English, this means that you can build APIs that bounded contexts use to communicate, and third parties can use those same APIs.
p315: By isolating bounded contexts each owned by a single team, loose coupling is within reach. Each team is free to develop its features in line with its business priorities, free of cross‐team distractions or dependencies.
p320: This follows the convention of naming API projects based on the format {bounded context}.{Resource}.
p340: Accordingly, for an event‐driven REST system, you can use a similar naming convention that communicates domain concepts, such as {BoundedContext}.{BusinessComponent}. {Component}.
p489: The domain model for the Listing bounded context. (Domain – Bounded Context – Domain Model)

Domain-Driven-Design Tackling Complexity in the Heart of Software by Eric Evans 2003

p239: By explicitly defining a BOUNDED CONTEXT within which a model applies and then, when necessary, defining its relationship with other contexts, the modeler can avoid bastardizing the model.
p304: Code reuse between BOUNDED CONTEXTS is a hazard to be avoided. Integration of functionality and data must go through a translation.
p339: Generally speaking, there is a correspondence of one team per BOUNDED CONTEXT . One team can maintain multiple BOUNDED CONTEXTS, but it is hard (though not impossible) for multiple teams to work on one together.
p341: The feasibility of a deployment plan should feed back into the drawing of the CONTEXT boundaries. When two CONTEXTS are bridged by a translation layer, one CONTEXT can be updated just so a new translation layer provides the same interface to the other CONTEXT. A SHARED KERNEL imposes a much greater burden of coordination, not just in development but also in deployment. SEPARATE WAYS can make life much simpler.
p419: Of course, because each BOUNDED CONTEXT is its own name space, one structure could be used to organize the model within one CONTEXT, while another was used in a neighboring CONTEXT, and still another organized the CONTEXT MAP.

Implementing Domain-Driven Design by Vaughn Vernon 2013

p23: You get more than a team lingo. The Language of a team in an explicit Bounded Context expressed as a domain model adds true business value and gives us certainty that we are implementing the correct software.
p38: Strategic Modeling: A Bounded Context is a conceptual boundary where a domain model is applicable. It provides a context for the Ubiquitous Language that is spoken by the team and expressed in its carefully designed software model.
p39: Architecture: It’s important to keep in mind that your strategically and tactically designed domain models should be architecturally neutral. A powerful architectural style for hosting a Bounded Context is Hexagonal, which can be used to facilitate other styles such as Service-Oriented, REST and Event-Driven, and others.
p40: Tactical Modeling: We model tactically inside a Bounded Context using DDD’s building block patterns. One of the most important patterns of tactical design is Aggregate.
p47: For now think of a Bounded Context as a conceptual boundary around a whole application or finite system. The reason for this boundary is to highlight that every use of a given domain term, phrase, or sentence —the Ubiquitous Language— inside the boundary has a specific contextual meaning. Any use of the term outside that boundary could, and probably does, mean something different.
p50: When trying to discover the Aggregates in a Bounded Context (2), we must understand the model’s true invariants. Only with that knowledge can we determine which objects should be clustered into a given Aggregate.
p70: Figure 2.2. An abstract business Domain that includes Subdomains and Bounded Contexts – nice picture with subdomains en bounded contexts!
p76: The solution space is one or more Bounded Contexts, a set of specific software models. That’s because the Bounded Context is a specific solution, a realization view, once developed. The Bounded Context is used to realize a solution as software.
p81: Thus, a Bounded Context is principally a linguistic boundary.

Strategic Monoliths and Microservices by Vernon, Jaskula 2022

p125: The Bounded Context, for example, is a top-level, coarse-grained module where a business capability is housed.
p128: The only design driving force for Bounded Contexts should be the scope of the business capability and its Ubiquitous Language, and not the size.

Learning Domain-Driven Design by Vlad Khononov 2021

p41: …a bounded context can contain multiple subdomains.
p58: When a system’s bounded contexts encompass multiple subdomains, there can be multiple integration patterns at play.
p225: …bounded contexts protect the consistency of ubiquitous language and models.
p290: A bounded context is a boundary of a model, and a model is only applicable in its bounded context. Bounded contexts are implemented in independent project/solutions, thus allowing each bounded context to have its own development lifecycle. Finally, a bounded context should be implemented by a single development team, and therefore, it is also an ownership boundary.

Designing Secure Architecture of Health Software using Agile Practices

p272: Bounded contexts introduce boundaries for terms of the ubiquitous language to prevent ambiguity in software artefacts. More specifically, the solution space is broken down into several bounded contexts, each solving one (or several) sub-domains in a highly cohesive manner without any linguistic ambiguity.
p273: Therefore, because a bounded context solves one or several sub-domains, it comprises together with the implementing adapters of the ports it defines, a full aspect of the complete system.
p275: Recall that a bounded context implementation is independent of all other concerns and can function in isolation. Particularly, it does not depend on the front-end which visualizes or provides access to the domain information.

Are Single-Page Applications Bounded Contexts – and what the heck is a Bounded Context?

A Bounded Context is a part of the system where the same people work on the same things and call those things by the same names.

DDDcrew – The Bounded Context Canvas

A bounded context is a sub-system in a software architecture aligned to a part of your domain..

Strategic Domain-Driven Design

A bounded context is a distinct part of the domain in which a particular subset or dialect of the ubiquitous language is consistent at all times.

Systems Thinking by combining Team Topologies with Context Maps

A Bounded Context is a boundary for a model expressed in a consistent language tailored around a specific purpose.

Getting modules right with Domain-driven Design by Michael Plöd 2022

What is a tomato – a fruit or vegetable?

Context Mapper – Bounded Context by Stefan Kapferer 2023

There are four bounded contexts types: Feature, Application, System, Team

An incomplete list of Bounded Context examples as found in the canonical DDD literature:

Bounded Context	Source & Domain object & Remarks
Booking	[Evans 2003] p16 (‘Passenger’) [Evans 2003] p370 [Millett 2015] p866
Billing	[Khononov 2022] p91 (with context map) [Khononov 2022] p238
Catalogue	[Millett 2015] p227 [Khononov 2022] p238
CRM	[Millett 2015] p100 (Customer model shared kernel with Bounded Context Commerce) [Vernon 2013] p190 [Zimarev 2019] p410 [Khononov 2022] p70 [Khononov 2022] p91 (with context map) [Khononov 2022] p238 [Khononov 2022] p321
Customer Service	[Khononov 2022] p76 (‘Ticket’) Fowler 2014 (‘Product’, ‘Customer’)
HR	[Khononov 2022] p96 (Employee model as shared kernel with Bounded Context Payroll)
Identity & Access	[Khononov 2022] p91 (with context map) [Vernon 2013] p74
Inventory	[Millett 2015] p81 (‘Product’) [Vernon 2013] p69 [Zimarev 2019] p410
Marketing	[Millettt 2019] p16 (‘Subscriber’) [Millett 2015] p81 (‘Product’) [Khononov 2022] p64 (‘Lead’) [Khononov 2022] p91 (with context map)
Ordering	[Millett 2015] p88
Payroll	[Millett 2019] p20 (Employee model as shared kernel with Bounded Context Employee Management) [Millett 2015] p96 (Employee model as shared kernel with Bounded Context Payroll)
Procurement	[Millett 2015] p98 [Millett 2015] p81 (‘Product’)
Promotions	[Millett 2015] p660 [Millett 2015] p88 [Khononov 2022] p300 (‘Lead’, ‘Campaign’)
Pricing	[Millett 2015] p81 (‘Product’) [Millett 2015] p88 [Millett 2015] p227
Purchasing	[Vernon 2017] p79
Sales	[Millett 2019] p8 (‘Lead’) [Millett 2015] p76 (‘Ticket’) [Zimarev 2019] p410 [Khononov 2022] p64 (‘Lead’) [Khononov 2022] p300 (‘Lead’, ‘Campaign’) Fowler 2014 (‘Product’, ‘Customer’)
Shipping	[Millett 2015] p86 (‘Product’)