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Gartner’s View of Enterprise Architecture

I had the opportunity today to attend a very interesting seminar on enterprise architecture, held by Massimo Pezzini, an analyst with Gartner. The following will be a summary along with some thoughts.

Early in his presentation, he listed three major elements of enterprise architecture: Design Patterns, Information Architecture, and Technical Architecture. He explained design patterns as being “reusable, logical concepts,” and named as examples of these, two-tier/multitier architectures, fat/thin clients, and centralized/decentralized architectures. Information Architecture contains various models of the enterprise, such as object, data, and process models. He called this “blueprints.” Technical Architecture, finally, is the platform, developer tools, database servers, middleware, etc., in the form of a “standard ‘buy list’.”

Diagram comparing Gartner's and Philippe Kruchten's models

This reminded me of Philippe Kruchten’s “4+1 View Model of Software Architecture” (PDF). In his model, there are four views: the Physical, Logical, Process, and Development views, along with a fifth (the ”+1” part) being comprised of use-cases and labeled “Scenarios.” The Physical and Development views would map fairly directly onto Pezzini’s Technical Architecture, whereas the three others correspond to both of Design Patterns and Information Architecture. I think it’s interesting that Design Patterns is an element of its own, as this indicates that wherever possible, concepts should be codified as patterns and shared within the enterprise, and hopefully even beyond the enterprise.

A central idea in Massimo Pezzini’s presentation was that it isn’t possible to do “classical” architecture in the larger scale, where different systems, existing and future ones, each belonging to different organizations, are to interact with each other. What he meant by this was that you can’t enforce an architecture on all of these systems. To use his terms, you can’t dictate a list of design patterns that must be used, specify various models of some generic organization which every organization must mimic (the Information Architecture), and a standard platform that all systems must be deployed on (the Technical Architecture). Therefore, he introduces the metaphor of city planning.

A picture of Chicago

So, how is city planning different from architecture? Architecture in fact often includes city planning, but here the city planning metaphor refers to an overall plan, a framework of guidelines and rules, within which several architectures are created. This is something I have thought about in the past, specifically when reading Jane Jacobs’s book, The Death and Life of Great American Cities. Using this metaphor makes it clear that the overall plan cannot dictate specific details of the systems to be built. A city plan can only provide guidelines to ensure that the buildings will “work,” harmonize, together as well as with surrounding, already existing buildings.

Massimo Pezzini listed three levels of architecture, where city planning was the third. The first level was the architecture of a single system, and the second the architecture for a set of related systems. A single system would require only one architect, whereas a team of architects would have to cooperate to create the architecture for a family of systems. On the third level, as mentioned, it’s impossible to have only one architecture; instead, there are many architectures, each created within the overall “city plan,” by an architect working independently of other architects. Pezzini called them autonomous architects.

Three levels of architecture

I will continue this summary/commentary tomorrow. Meanwhile, I searched through my archives for things about urban planning as a metaphor for software architecture, and found two notes from when I read Christopher Alexander’s very interesting essay A City is not a Tree, as well as several reading notes on Jane Jacobs’s book. I’ll take a closer look at these as well.

1 Photograph of Chicago taken by “lobster,” found at stock.xchng.

The above was posted to my personal weblog on March 24, 2004. My name is Peter Lindberg and I am a thirtysomething software developer and dad living in Stockholm, Sweden. Here, you’ll find posts in English and Swedish about whatever happens to interest me for the moment.

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