1.3 The Four Architecture Domains & Architecture Abstraction
Key Takeaways
- The four architecture domains supported by the TOGAF Standard are Business, Data, Application, and Technology Architecture.
- Data Architecture and Application Architecture together form the Information Systems Architectures developed in ADM Phase C.
- Architecture abstraction is a technique for dividing a problem area into smaller problem areas that are easier to model and solve.
- The TOGAF Standard, 10th Edition defines four abstraction levels: Contextual (Why), Conceptual (What), Logical (How), and Physical (With what).
- The logical level identifies implementation-independent components, while the physical level allocates the physical components that realize them.
1.3 The Four Architecture Domains & Architecture Abstraction
Learning Unit 1 expects you to list the four architecture domains commonly accepted as subsets of an overall Enterprise Architecture, and to briefly describe how architecture abstraction is used. The 10th Edition wording matters: abstraction has four levels — Contextual, Conceptual, Logical, and Physical — answering Why, What, How, and With what.
The Four Architecture Domains
TOGAF supports four domains that are commonly accepted as subsets of an overall Enterprise Architecture:
| Domain | What the TOGAF Standard says it covers | Glossary definition (summary) |
|---|---|---|
| Business Architecture | Defines the business strategy, governance, organization, and key business processes | A representation of holistic, multi-dimensional business views of capabilities, end-to-end value delivery, information, and organizational structure, and their relationships to strategies, products, policies, processes, initiatives, and stakeholders |
| Data Architecture | Describes the structure of an organization's logical and physical data assets and data management resources | A description of the structure of the enterprise's major types and sources of data, logical data assets, physical data assets, and data management resources |
| Application Architecture | Provides a blueprint for the individual applications to be deployed, their interactions, and their relationships to the core business processes | A description of the structure and interaction of the applications that provide key business capabilities and manage the data assets |
| Technology Architecture | Describes the digital architecture and the logical software and hardware infrastructure capabilities and standards needed to support the deployment of business, data, and application services — including digital services, IoT, social media infrastructure, cloud services, IT infrastructure, middleware, networks, communications, and processing | A description of the structure and interaction of the technology services and technology components |
In the ADM, Phase B develops Business Architecture, Phase C develops the Information Systems Architectures (Data Architecture and Application Architecture), and Phase D develops Technology Architecture.
Other Domains Built from the Four
The standard notes that many other domains can be defined by combining appropriate views of the four. Its examples are Information Architecture, Risk and Security Architectures, and Digital Architecture. The glossary also notes that other domains, such as motivation, security, and governance, may span the four primary domains.
How the Domains Relate
- Business drives the others. Business Architecture is developed first in the standard ADM flow and provides the context and requirements for Information Systems and Technology work.
- Data and applications are interdependent. Applications create and use data; data needs applications to deliver value. That is why both sit in Phase C.
- Technology enables everything above it. Technology Architecture provides the services and components on which applications and data are deployed.
- Iteration is normal. A technology constraint discovered in Phase D can send architects back to revisit Phase C or B.
Architecture Abstraction
The standard defines architecture abstraction as an architectural technique for dividing a problem area into smaller problem areas that are easier to model and therefore easier to solve. Abstraction levels are layered, moving from high-level models to more detailed models, and they cross all four domains.
| Level | Question | Focus in the TOGAF Standard |
|---|---|---|
| Contextual | Why is the architecture needed? | Understanding the environment in which the enterprise operates and the context in which architecture work is planned and executed: why the work is undertaken, its scope, and the motivation in terms of goals, drivers, and objectives |
| Conceptual | What functionality and other requirements need to be met? | Decomposing requirements to understand the problem and what is needed to address it, without focusing on how it will be realized; usually modeled with service models (business, application, technology services). Also called service abstraction or behavior abstraction |
| Logical | How do we structure the functionality? | Identifying the kinds of business, data, application, and technology components needed to achieve the conceptual services, in an implementation-independent fashion; several logical solution alternatives may exist |
| Physical | With what assets shall we implement this structure? | Allocating and implementing physical components to meet the identified logical components; many physical alternatives may exist |
The standard adds a caution: why, what, and how here have no connection to their use in the Zachman® Framework.
How Abstraction Is Used
- Communication: each stakeholder group can engage at a consistent level of detail — executives at contextual and conceptual levels, solution teams at logical and physical levels.
- Decision quality: separating logical from physical keeps product choices from driving requirements too early.
- Alternatives: because several logical and physical groupings are possible, abstraction makes trade-offs visible.
- Consistency: the glossary notes that a "level of abstraction" provides a consistent, common level of detail across the architecture, which is especially useful for large and complex architectures.
Worked Example: Customer Onboarding
| Level | Business | Data | Application | Technology |
|---|---|---|---|---|
| Contextual (Why) | Goal: cut account-opening time; driver: digital competitors | Driver: regulatory identity checks | Objective: remove manual re-keying | Objective: scale for peak demand |
| Conceptual (What) | Business service: Open Customer Account | Information need: verified customer identity | Application service: Identity Verification | Technology service: secure hosting |
| Logical (How) | Logical component: onboarding function and roles | Logical data component: Customer | Logical application component: onboarding service | Logical technology component: container platform |
| Physical (With what) | Named teams and procedures | Specific database schema | Specific product or code base | Specific cloud region and platform product |
Common Exam Pitfalls
- Using only three abstraction levels. The 10th Edition has four: Contextual, Conceptual, Logical, Physical.
- Matching the questions wrongly. Contextual = Why; Conceptual = What; Logical = How; Physical = With what.
- Calling the conceptual level "technology-neutral components." Components belong to the logical level; the conceptual level is about required services and behavior.
- Forgetting where the domains sit in the ADM. Data and Application Architecture are both Phase C, the Information Systems Architectures phase.
Which set lists the four architecture domains that the TOGAF Standard supports as commonly accepted subsets of an overall Enterprise Architecture?
In the TOGAF Standard, 10th Edition, which question does the Logical abstraction level answer?
An architect models the business, application, and technology services an initiative requires, without yet deciding how they will be grouped into components. Which abstraction level is being used?
Which statement about the Information Systems Architectures in the ADM is correct?