Since Stephen Spewak's book called enterprise architecture planning (EAP) in 1993,2 and perhaps before then, it has been normal to recognise four types of architecture domain. The British Computer Society's "Reference Model for Enterprise and Solution Architecture" also follows this subdivision but additionally mentions the (single) application architecture level just below the applications architecture as well as the domains of information architecture, information systems architecture, or security architecture (a cross-cutting concern):3
Note that the applications architecture is about the application portfolio, not the internal architecture of a single application - which is often called the application architecture.
Many EA frameworks combine data and application domains into a single layer, sitting below the business (usually a human activity system; that is a notational system expressing a purposeful human activity in a theoretical way using intellectual constructs and not descriptions of actual real-world activity4) and above the technology (the platform IT infrastructure). There are many variations on this theme.
N. Dedic, "FEAMI: A Methodology to include and to integrate Enterprise Architecture Processes into Existing Organizational Processes," in IEEE Engineering Management Review, doi: 10.1109/EMR.2020.3031968. ↩
Steven Spewak; S. C. Hill (1992). Enterprise Architecture Planning: Developing a Blueprint for Data, Applications, and Technology. Boston, QED Pub. Group. ISBN 978-0-471-59985-2. 978-0-471-59985-2 ↩
"Reference Model for ISEB Certificates in Enterprise and Solution Architecture Version 3.0" (PDF). bcs. 2010. http://www.bcs.org/upload/pdf/reference-model-enterprise-solution-architecture.pdf ↩
Human activity systems - Systems Thinking, Systems Practice, Peter Checkland, 1981, page 115, 314 http://www.perflensburg.se/Privatsida/cp-web/capchasy.htm ↩