The schools are distinguished along two dimensions: scope and ends (purpose).
Enterprise wide IT platform (EIT). All components (software, hardware, etc.) of the enterprise IT assets.
Effective enterprise strategy execution and operation through IT-Business alignment. The end is to enhance business strategy execution and operations. The primary means to this end is the aligning of the business and IT strategies so that the proper IT capabilities are developed to support current and future business needs.
Enterprise (E). The enterprise as a socio-cultural—techno-economic system; hence ALL the facets of the enterprise are considered – the enterprise IT assets being one facet.
Effective enterprise strategy implementation through execution coherency. The end is effective enterprise strategy implement. The primary means to this end is designing the various facets of the enterprise (governance structures, IT capabilities, remuneration policies, work design, etc.) to maximize coherency between them and minimize contradictions.
Enterprise-in-environment (EiE). Includes the previous scope but adds the environment of the enterprise as a key component as well as the bidirectional relationship and transactions between the latter and its environment.
Innovation and adaption through organizational learning.
The end is organizational innovation and adaption. The primary means is the fostering of organizational learning by designing the various facets of the enterprise (governance structures, IT capabilities, remuneration policies, work design, etc.) as to maximize organizational learning throughout the enterprise.
Besides scope and purpose, I have always considered it important to identify a third dimension of perspective (viewpoint). (For example, I talk about these three dimensions in my 1992 book on Information Modelling, pages 16-22.)
Among other things, perspective helps us to address the question: What kind of system is the enterprise being understood as? For example, the (micro-)economic perspective views the enterprise as a production system (value chain or value network), while the management cybernetic perspective (such as Stafford Beer’s Viable Systems Model) views the enterprise as a thinking system or brain. Gareth Morgan’s book Images of Organization contains a good survey of several contrasting perspectives.
Most enterprise architects in the first school adopt the traditional IT perspective of regarding the enterprise as an information processing system. Most of the well-known EA frameworks (such as those listed on the ISO 42010 website) are solidly within the first school.
Lapalme’s second school explicitly invokes the socio-cultural perspective, and calls for all facets of the enterprise to be considered – this clearly implies going beyond the traditional IT perspective.
However, there is a considerable body of work that looks at the enterprise-in-environment, but remains within the IT perspective. This would include the Open Group work on the extended enterprise, as well as the Systems-of-Systems community. A key scoping question here is the exercise of governance over large distributed systems of systems. Mark Maier distinguished between directed and emergent systems (or we might think about directed and emergent enterprises), and this has been developed into a four-part schema by the US Department of Defense: Directed, Acknowledged, Collaborative and Virtual. Some useful work at the SEI, where this thinking has been connected into work on SOA and enterprise architecture.
Lapalme’s article identifies James Martin as one of the leaders of the third school, based on a minor work published in 1995, but most of Martin’s work belongs solidly within the first school. In his 1982 book, Strategic Data-Planning Methodologies, Martin shows how IBM’s BSP methodology could be used to decompose the activities of the organization, as a precursor to planning IT systems. The primary aim of such methodologies from the 1980s onwards was to identify opportunities to install more computers and develop more software, and I think it is no coincidence that a number of the pioneers of enterprise architecture (from Martin to John Zachman) had worked for IBM. See my note on The Sage Kings of Antiquity.
So I think it makes sense to divide Lapalme’s third school into two distinct sub-schools. There is clearly a lot of work in School Three A, which extends the scope of architecture without introducing the socio-cultural or other perspectives which Lapalme associates with School Two. There is as yet very little formal work in School Three B.
School Three A
School Three B
James Lapalme, “3 Schools of Enterprise Architecture,” IT Professional, 14 Dec. 2011. IEEE computer Society Digital Library. IEEE Computer Society, http://doi.ieeecomputersociety.org/10.1109/MITP.2011.109