Whatever their nature, architectures can be defined as structured collections of assets and mechanisms shared by a set of active entities with common purposes: houses for dwelling, factories for manufacturing processes, office buildings for administrative ones, human beings for living, etc.

Along that reasoning enterprises architectures should be defined in terms of one distinction and three layers:
- A distinction between specific and changing business contexts and opportunities on one hand, shared and stable capabilities on the other hand (represented with the Zachman’s framework above).
- The enterprise layer deals with the representation of business environment and objectives (aka business model), organization and processes.
- The system layer deals with the functionalities of supporting systems independently of platforms.
- The platform layer deals with actual systems implementations.
It must be noted that while the layered perspective is widely agreed (names may differ), taxonomies often overlap.
Further Reading
- Thread: Enterprise Architecture
- Models, Architectures, Perspectives (MAPs)
- Views, Models, & Architectures
- EA: The Matter of Layers
- Architecture Capabilities
- Feasibility & Capabilities
- Abstractions & Emerging Architectures
- Enterprise Systems & the OS Kernel Paradigm
- Agile Architectures: Versatility meets Plasticity
- Service Oriented Architectures
- EA: Maps & Territories
- EA: Work Units & Workflows
- EA: Legacy & Latency
- Relating to Functions
- Capabilities vs Processes
- From Processes to Services
- Alignment for Dummies
- Alignment: from Empathy to Abstraction