Modeling Languages: Differences Matter

“Since words are only names for things, it would be more convenient for all men to carry about them such things as were necessary to express a particular business they are to discourse on.”

Jonathan Swift, Gulliver’s Travels

Objective

Modeling languages are meant to support the description of contexts and concerns from specific standpoints. And because those different perspectives have to be mapped against shared references, language must also provide constructs for ironing out variants and factoring out constants.

Digging or Ironing out differences (Erwitt Elliott)

Ironing out differences in features and behaviors (Erwitt Elliott)

Yet, while most languages generally agree on basic definitions of objects and behaviors, many distinctions are ignored or subject to controversial understanding; such shortcomings might be critical when architecture capabilities are concerned:

  • Actual entities and their symbolic counterpart.
  • Actual entities and their roles.
  • Business logic and business operations
  • External events and system time.
Making Differences

Making Differences

As those distinctions set the backbone of functional architectures, languages should be assessed according their ability to express them unambiguously using the least possible set of constructs.

Business objects vs Symbolic Surrogates

As far as symbolic systems are concerned, the primary purpose of models is to distinguish between targets and representations. Hence the first assessment yardstick: modeling languages must support a clear and unambiguous distinction between objects and behaviors of concern on one hand, symbolic system surrogates on the other hand.

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A primer on representation: objects of concerns and surrogates

Yet, if objects and behaviors are to be consistently and continuously managed, modeling languages must also provide common constructs mapping identities and structures of actual entities to their symbolic counterpart.

Agents vs Roles

Given that systems are built to support business processes, modeling languages should enable a clear distinction between physical entities able to interact with systems on one hand, roles as defined by enterprise organization on the other hand.

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Agents and Roles

In that case the mapping of actual entities to systems representations is not about identities but functionalities: a level of indirection has to be introduced between enterprise organization and system technology because the same roles can be played,simultaneously or successively, by people, devices, or other systems.

Business logic vs Business operations

Just like actual objects are not to be confused with their symbolic description, modeling languages must make a clear distinction between business logic and processes execution, the former defining how to process symbolic objects and flows, the latter with the coupling between process execution and changes in actual contexts. That distinction is of a particular importance if business and organizational decisions are to be made independently of supporting systems technology.

Pull vs Push Rule Management

Business logic and operational contingencies

Language constructs must also support the consolidation of functional and operational units, the former being defined by integrity constraints on symbolic flows and roles authorizations on objects and operations, the latter taking into account synchronization constraints between the state of actual contexts and the state of their system symbolic counterpart. And for that purpose languages must support the distinction between external and internal events.

External vs Internal Events

Paraphrasing Albert Einstein, time is what happens between events. As a corollary, external time is what happens between context events, and internal time is what happens between system ones. While both can coincide for single systems and locations, no such assumption should be made for distributed systems set in different locations. In that case modeling language should support a clear distinction between external events signalling changes set in actual locations, and internal events signalling changes affecting system surrogates.

Time scales can be design on purpose

Time scales are set by events and concerns

Along that perspective synchronization is to be achieved through the consolidation of time scales. For single locations that can be done using system clocks, across distributed locations the consolidation will entail dedicated time frames and mechanisms set in reference to some initial external event.

Conclusion: How to share differences across perspectives

Somewhat paradoxically, multiple modeling languages erase differences by paring down shared descriptions to some uniform lump that can be understood by all. Conversely, agreeing on a set of distinctions that should be supported by every language could provide an antidote to the Babel syndrome.

That approach can be especially effective for the alignment of enterprise and systems architectures as the four distinctions listed above are equally meaningful in both perspectives.

Further reading

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