Monday, June 27, 2011

Gestalt-Driven Development: Memes, Alleles and Architectural Fitness

Claiming that Evolution is merely a “theory” is akin to claiming the same about Gravity. Evolution is a beautiful and elegant idea, which also happens to precisely describe and predict how living organisms change and diversify over time in Meatspace. It is also a fabulously useful metaphor outside the realm of biology, and I have appropriated it, along with Memetics as cornerstones of Gestalt-Driven Development.

Note: I have only provided definitions of new terms I have introduced or terms that I have subtly changed. For formal definitions of common terms follow the links to the appropriate entries in the Encyclopaedia Galactica.

A Software Architect typically has a number of products, technologies, approaches, patterns, practices, processes, methodologies, frameworks, libraries, algorithms and languages in their Software Architect’s “toolbox”. All of the aforementioned have a lifecycle; they are added  as new software paradigms emerge or become fashionable, refined and expanded as they mature, then used less as they go out of fashion, and finally relegated to the bottom of the toolbox or discarded entirely when they are no longer relevant. The contents of this toolbox can be thought of as Architectural Memes.

Architectural Memes that are repetitively used together form an Architectural Meme Complex or Memeplex. A simple example of a Memeplex would be C#, WF, WCF, OOP, Windows Server AppFabric, SQL Server and Visual Studio. Another would be HTML5, SVG, CSS3, DRY, JavaScript, jQuery, and AJAX.

Architectural Memes and Memeplexes will be more or less appropriate for a system given how well they meet the requirements of that system or part thereof. The measure of how well a given Architectural Meme or Memeplex meets the requirements of a system, sub-system or component is measured against the Fitness Criteria for that system, sub-system or component. The Fitness Criteria represent the requirements of the software system, expressed in such a way that the relative fitness of any given Architectural Meme or Memeplex can be quantified.

Obviously there exist overlapping or competitive Architectural Memes and Memeplexes, i.e. they can be used to address the same requirements. These are Meme Alleles. Meme Alleles are Memes or Memeplexes that can be used to meet similar requirements, and who’s Architectural Fitness will be evaluated using the same set of Fitness Criteria. An over-simplified example of Architectural Alleles would a Relational Database (RDBMS) implementation and a NoSQL database implementation given the following fitness criterion:  Enterprise-scale storage and retrieval of structured data. RDBMS products from different companies would also be Memetic Alleles in this case.

Note: A Gene and a Meme are not entirely analogous. A Meme is technically analogous to an instance of a Gene, an Allele, rather than the Gene itself. Hopefully scholars of Genetics and Memetics will forgive the minor poetic licence that I am taking with my definition of Meme Allele.

As I mentioned before Architectural Memes are not limited to technologies; they include processes and practices e.g. Waterfall and Agile, which will have better or worse fitness depending on the nature of the software being developed, management or the client’s ability/willingness to embrace the uncertainty innate in software development, the geographic and cultural distribution of the team, etc. Architectural Memes also include approaches, patterns and frameworks, e.g.  OOP, SOLID, GRASP, ESB, SOA, MVC, MVP, MVVM, BDD, FDD, DDD, TDD, TOGAF, ITIL, and many, many more wonderfully hermetic acronyms.

In Gestalt-Driven Development it is the task of the Software Architect (and the whole software engineering team) to identify the Memes and Meme Complexes that might be applicable to the system, ascertain the fitness of those Memes to derive the set of appropriate building blocks, and then compose those building blocks into a System Architecture, or Phenotype. Obviously this requires that the requirements have been transformed and refactored into one or multiple sets of Fitness Criteria. This is a shared task that starts with requirements analysis and ends with the engineering team.  

Using Gestalt-Driven Development and the metaphor outlined above a Software Architect is able to test and verify the suitability of an architecture to the requirements of the system early in the development process and continuously evolve that architecture throughout the process as requirements mutate and emerge.

Note: Obviously random mutation of code and data are not a good thing in all but the rarest cases. GDD proposes a high level approach to software development and architecture, not the use of genetic algorithms (though it does not preclude their use).

I am still in the process of formalizing GDD so I will definitely post a lot more about it in the future.


  1. I would agree on the gravity...

  2. Does that mean you disagree with EVERYTHING else?

  3. After reading this through again I have decided that the currently accepted definition of "Meme" could do with an overhaul. The current definition of "Meme" is analogous to an "Allele", not a "Gene". It would certainly help my use of Memetics in GDD; A "Meme" would be a set of software requirements and constraints, and an "Allele" would be software, processes, practices, etc. that addressed the aforementioned.