The Six Interrogatives of Zachman: What, How, Where, Who, When, Why

The Zachman Framework's six interrogatives - What, How, Where, Who, When, Why - are the six fundamental questions that must be answered to describe any complex object comprehensively. These six columns form one axis of the 6x6 matrix and represent six distinct types of enterprise architectural knowledge.

Understanding each interrogative is the key to populating and using the Zachman Framework effectively.

Introduction: The Interrogative Approach

The six interrogatives originate from classical rhetoric and journalism. They are the fundamental questions a reporter asks to understand an event:

What happened? - The action or event itself
How did it happen? - The mechanism or process
Where did it happen? - The location or geography
Who was involved? - The people or roles
When did it happen? - The timing or sequence
Why did it happen? - The motivation or cause

John Zachman applied these universal questions to enterprise architecture. By ensuring that every aspect of the enterprise is described across all six interrogatives, an architect guarantees completeness and prevents blind spots.

The Six Interrogatives Explained

Interrogative 1: WHAT - Data and Inventory

The question: What things (entities, data, inventory) does the enterprise consist of?

What this column addresses:

Data entities and their attributes
Entity relationships (what relates to what)
Classification of data types
Business objects and data models
Metadata (data about data)
Information flows and data stores

Manifestations across perspectives:

Row 1 (Planner): Entity list - all the nouns the business cares about (customers, orders, products, accounts)
Row 2 (Owner): Business entity-relationship model - how business entities relate (e.g., a customer has many orders)
Row 3 (Designer): Logical data model - system-independent logical entities and relationships
Row 4 (Builder): Physical data model - database schemas, DDL (Data Definition Language)
Row 5 (Sub-Contractor): DDL scripts - actual CREATE TABLE statements, indexes, constraints
Row 6 (Enterprise): Live database - the actual operating data store

Why it matters: Understanding "What" prevents data silos, reduces duplication, and enables data governance and reuse.

Interrogative 2: HOW - Function and Process

The question: How does the enterprise function and operate?

What this column addresses:

Business processes and value chains
System functions and capabilities
Application logic and workflows
User workflows and procedures
Data transformations and algorithms
Control flows and process steps

Manifestations across perspectives:

Row 1 (Planner): Process list - high-level business processes (e.g., "Order Management," "Billing," "Accounts Receivable")
Row 2 (Owner): Business process model - detailed business processes with steps, actors, and decisions (e.g., how a customer order flows from receipt to fulfillment)
Row 3 (Designer): Logical system model - system functions independent of technology (e.g., "Validate Order," "Calculate Tax," "Allocate Inventory")
Row 4 (Builder): Application design - specific system implementations and algorithms (e.g., validation rules in Java, tax calculation in SQL)
Row 5 (Sub-Contractor): Code and algorithms - the actual implementation (source code, procedures)
Row 6 (Enterprise): Running applications - the actual operating system

Why it matters: Understanding "How" prevents process fragmentation, enables continuous improvement, and aligns processes with business strategy.

Interrogative 3: WHERE - Network and Location

The question: Where are the enterprise's operations, systems, and infrastructure physically distributed?

What this column addresses:

Geographic locations and facilities
Network topology and distribution
System deployment across sites
Data centre locations
Remote vs local processing
Physical infrastructure (servers, networking equipment)

Manifestations across perspectives:

Row 1 (Planner): Site list - all locations where the business operates (e.g., headquarters, regional offices, data centres)
Row 2 (Owner): Logistics network - how business processes are geographically distributed (e.g., which factories produce which products, which warehouses stock which regions)
Row 3 (Designer): System distribution model - which systems exist at which locations, logical network architecture
Row 4 (Builder): Infrastructure model - physical network topology, data centre locations, server placement, disaster recovery sites
Row 5 (Sub-Contractor): Configuration details - specific network addresses, routing tables, firewall rules, physical cabling
Row 6 (Enterprise): Live infrastructure - the actual deployed and operating network

Why it matters: Understanding "Where" enables efficient resource allocation, disaster recovery planning, compliance with data residency requirements, and optimisation of network performance.

Interrogative 4: WHO - People and Organisation

The question: Who performs the work? Who makes decisions? How is the organisation structured?

What this column addresses:

Organisational structure and reporting lines
Roles and responsibilities (RACI models)
User communities and personas
Access control and permissions
User interfaces and interactions
Skill requirements and training

Manifestations across perspectives:

Row 1 (Planner): Organisational chart - high-level structure (e.g., business units, departments)
Row 2 (Owner): Detailed roles and responsibilities - who does what, decision-making authority (e.g., who approves orders, who sets prices)
Row 3 (Designer): System access model - who accesses which system functions, role-based access control (RBAC) design
Row 4 (Builder): Security architecture - user authentication methods, authorisation mechanisms, security policies
Row 5 (Sub-Contractor): Access controls - specific user accounts, permissions, security credentials
Row 6 (Enterprise): Live authentication - actual logged-in users, active sessions, operating permissions

Why it matters: Understanding "Who" enables proper governance, security, change management, and ensures that the right people have the right access to the right information.

Interrogative 5: WHEN - Time and Schedule

The question: When do things happen? What is the timing and sequencing of events and processes?

What this column addresses:

Event timing and schedules
Business cycles and seasonality
System scheduling and batch processes
Trigger conditions and sequences
Timing constraints and SLAs
Asynchronous vs synchronous processing
Historical and temporal data

Manifestations across perspectives:

Row 1 (Planner): Event list - key business events and their frequency (e.g., "Month-end close," "Annual physical inventory," "Quarterly earnings report")
Row 2 (Owner): Business event model - when events occur, what triggers them, what response they require (e.g., "When a customer places an order, the inventory must be reserved within 5 minutes")
Row 3 (Designer): Processing sequence model - system timing and event sequences, state machines, workflow states
Row 4 (Builder): System scheduling - batch windows, ETL schedules, message queue timings, database maintenance windows
Row 5 (Sub-Contractor): Timing specifications - cron jobs, job scheduler configurations, queue processing parameters
Row 6 (Enterprise): Live scheduling - actual running jobs, real-time event processing, operating timing

Why it matters: Understanding "When" enables efficient resource scheduling, SLA compliance, capacity planning, and real-time responsiveness to business events.

Interrogative 6: WHY - Motivation and Strategy

The question: Why does the enterprise exist and operate as it does? What motivates architectural decisions?

What this column addresses:

Business goals and strategy
Business rules and constraints
Regulatory requirements and compliance
System constraints and dependencies
Decision rules and policies
Risk and security considerations
Non-functional requirements (performance, availability, scalability)

Manifestations across perspectives:

Row 1 (Planner): Goal list - high-level business strategy (e.g., "Increase market share," "Reduce operating costs," "Improve customer satisfaction")
Row 2 (Owner): Business rules and strategy - detailed business rules that drive operations (e.g., "Customers in Europe pay in Euros," "Orders must be fulfilled within 48 hours," "No orders from sanctioned countries")
Row 3 (Designer): System constraints and requirements - non-functional requirements (e.g., "System must support 10,000 concurrent users," "99.99% availability," "Response time < seconds")
Row 4 (Builder): Technology choices justified by business rules - specific technology decisions driven by constraints (e.g., "We chose cloud for elasticity," "We chose Oracle for financial reporting compliance")
Row 5 (Sub-Contractor): Implementation rules - specific implementation decisions (e.g., connection pool sizes, caching strategies, failover logic)
Row 6 (Enterprise): Operational constraints - actual business rules enforced in the running system (e.g., interest rate calculations, approval thresholds)

Why it matters: Understanding "Why" ensures that architecture decisions are grounded in business value, enables stakeholder alignment on priorities, and provides a foundation for change management.

How the Six Interrogatives Work Together

The power of the six interrogatives lies in their complementarity. No single interrogative is sufficient:

Knowing What (entities) but not How (processes) means you understand the data but not the operations.
Knowing How but not Where means you understand processes but not distribution.
Knowing Where but not Who means you understand locations but not accountability.
Knowing Why but not What, How, Where, When means you understand motivation but cannot execute.

By addressing all six interrogatives for each perspective (Row 1-6), an architect ensures a complete description of the enterprise.

Practical Example: Retail Order Management

Let's see how the six interrogatives apply to a simple retail order management process:

Interrogative	Description
What	Customers, Orders, Products, Inventory, Payments, Shipments
How	Customer browses → adds to cart → checks out → payment processed → inventory deducted → shipment prepared → delivery
Where	Web site (cloud), inventory in 5 regional warehouses, customer homes, payment processor
Who	Customers, warehouse staff, customer service reps, shipping carriers, payment processor
When	Orders received 24/7; inventory updated real-time; shipments prepared daily; deliveries within 48 hours
Why	Maximise sales, minimise inventory costs, reduce delivery time, ensure payment security

To fully architect the retail order system, you must describe it across all six interrogatives and all six perspectives (rows). Omitting any dimension creates architectural gaps.

The Six Interrogatives as a Completeness Checklist

When developing enterprise architecture, use the six interrogatives as a checklist:

Have I described What (all relevant entities and data)?
Have I described How (all key processes and workflows)?
Have I described Where (all geographic and network distribution)?
Have I described Who (all roles and access controls)?
Have I described When (all timing and sequencing concerns)?
Have I described Why (all business rules and constraints)?

If you cannot confidently answer "yes" to all six, your architecture is incomplete.

Common Mistakes: When Interrogatives Are Neglected

Neglecting What: Multiple data silos with duplicate entities. Poor data governance.
Neglecting How: Process fragmentation. Lack of workflow visibility.
Neglecting Where: Inefficient distribution. Poor disaster recovery.
Neglecting Who: Security gaps. Accountability unclear.
Neglecting When: Missed SLAs. Scheduling conflicts.
Neglecting Why: Architecture decisions not aligned with business value. Scope creep.

Interrogatives Across Industries

The six interrogatives apply universally:

Hospital: What (patients, medications, procedures) | How (admit, diagnose, treat, discharge) | Where (wards, operating rooms, labs) | Who (doctors, nurses, patients) | When (emergency, scheduled, rounds) | Why (patient safety, regulatory compliance, cost control)

Government Agency: What (citizens, benefits, licenses) | How (apply, verify, distribute, renew) | Where (offices, online portals, satellite offices) | Who (staff, citizens, partner agencies) | When (application windows, processing timelines) | Why (public service, budget constraints, legal mandates)

Key Takeaways

The six interrogatives are universal: They apply to any enterprise, any industry, any technology.
Each interrogative addresses a distinct dimension: What, How, Where, Who, When, Why each provide unique architectural value.
All six are necessary: Omitting any interrogative creates architectural blind spots.
Combined with six perspectives, they form the complete matrix: Each cell (interrogative x perspective) represents a specific artefact type.
Use them as a completeness checklist: Before declaring your architecture complete, verify you have addressed all six.

Next Steps

Explore Each Interrogative in Depth for detailed dives into What, How, Where, Who, When, and Why columns.
Read Six Perspectives to understand the rows that combine with these columns.
Jump to Practical Application to see real examples of populating these cells.
Explore Artifacts and Deliverables to understand what specific models go in each cell.

The six interrogatives are the foundation of the Zachman Framework. Once you internalise them, understanding the full 6x6 matrix becomes straightforward.

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