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Modularity is a key aspect of business architecture. The more a product or system is broken down into subsystem or modules with compatible joining rules the more flexibility there is to produce unique configurations of the system or reconfigure an existing system. Highly modular designs are more quickly and easily reconfigured to produce new functionality. Modularity enables flexibility. Modularity enables a cost effective increase in both complexity and variety - as in the case of mass customization.

Modular design (Baldwin, 1997) --
Modularity is a strategy for organizing complex products and processes efficiently.

A modular system is composed of units (or modules) that are designed independently but still function as a whole. Designers achieve modularity by partitioning information into visible design rules and hidden design parameters. Modularity is beneficial only if the partition is precise, unambiguous, and complete.

Visible design rules, also called visible information, are decisions that affect subsequent design decisions. They fall into three categories:

  • An architecture, which specifies what modules will be part of the system and what their functions will be.
  • Interfaces that describe in detail how the modules will interact, including how they will fit together, connect, and communicate.
  • Standards for testing a module's conformity to design rules (can the module function in the system) and for measuring one module's performance relative to another.

Hidden design parameters (hidden information), are decisions that do not affect the design beyond the local module.

Defining a modular architecture (Gilmore, 2000, Introduction) --
Characteristics of modules to be addressed when defining a modular architecture and interfaces:

  • An Connectivity, define all the modules that can precede, follow or operate in parallel with each module
  • Dependency define all the modules that must precede, follow, or operate in parallel with each module
  • Technical Linkage define how each module can be linked to preceding, following, and parallel modules (whether via human handling, expert system, configurator, communication technology, or other methods)
  • Performer define which individuals can perform activities in each module
  • Place define where activities in each module can be performed (for both physical and virtual space)
  • Communication mode defining how the status of the module is communicated during the linkage process (proactively, exception-based, look-up, etc.)
  • Ownership define who has responsibility for managing the activities within each module

Spectrum of modularity --
Modularity actually refers to the degree of 'tightness - looseness' by which components of a system are coupled. A system technically is not modular or not modular, but has degrees of high or low modularity. A system of low modularity, with 'tightly coupled' components, is referred to as an integrated system. On the other end of the spectrum, a highly modular system with 'loosely coupled' components is simply referred to as modular. The characteristics of the systems on either end of the spectrum are as follows --

  • Integrated system - 'tightly coupled' components --
    • the design is at one level, the system level
    • the system is non-decomposable
    • the innovation cost is high
    • the transformation cost is high
    • innovation is unconstrained
    • there is one configuration of components
    • an integrated product is not upgradeable
  • Modular system - 'loosely coupled' components --
    • the design is at two levels - the architecture (platform) level and the individual system level
    • the system is decomposable
    • the innovation cost, within the architecture, is low
    • the transformation cost is low
    • innovation is constrained by the architecture
    • there are multiple configurations of components
    • the system is easily upgraded