Conceptual Architecture: What

What is Conceptual Architecture?

“Conceptual Architecture” is the conceptual view(s) of the architecture of a system. It describes at a broad brushstrokes conceptual level the significant design ideas of the system. In particular, this view includes diagrams and text which identify, explicate, rationalize and contextualize the key structures and mechanisms of the system, and the relationships among them.

Conceptual Architecture expresses the key architectural elements and their relationships that give “shape” to the system. Each of these architectural elements, or abstractions, play a critical role in the system which is signified by their responsibility assignments. They collaborate and interact, and these relationships are a significant design consideration not only because interaction points (analogous to articulation points in physical systems) and “seams” in the system are non-trivial, but because interactions give rise to synergy that makes the system more than a simple aggregate of executing parts. The parts, their arrangement and concert, cohere within and give expression to the system “gestalt.”

Conceptual Architecture Diagram

The Conceptual Architecture Diagram renders the formative architectural abstractions (named boxes) and their interrelationships (lines). For complex systems, there may be a set of such diagrams, exploring the (de)composition of more complex, architecturally interesting architectural elements.

Component-Responsibility-Collaborator-Rationale (CRC-R) Descriptions

The Conceptual Architecture also identifies the responsibilities of each of the architectural elements. We advocate doing this on Component-Responsibility-Collaborator-Rationale (CRC-R) Descriptions* for each (conceptual architecture) component, so that the reasoning behind component design choices is captured along with the responsibilities (connecting the dots to desired outcomes, strategic decisions, lessons from experience and grounding assumptions, etc.), and dependencies and other relationships are also recorded. It is a simple and “just enough” format that matches the spirit and intent of Conceptual Architecture, supporting conception, communication and evolution of the key design ideas, including the fundamental organization, of the system.

Mechanism Sketches

Beyond the (set of) Conceptual Architecture Diagram(s) and CRC-R descriptions, architectural mechanisms (i.e., mechanisms of architectural significance) are sketched (in diagrams and descriptions) to conceive and convey their essential design nature — the design intent, contextual assumptions, structure, and “how it works” dynamic considerations. The capabilities of the system emerge from the inter- and intra-working of the parts of the system, and mechanisms allow us to focus on specific processes within the system, conceptually (at this point) designing architecturally significant functions of parts of the system.

Architecturally significant mechanisms are those that have more diffuse or systemic impact or are make-or-break important to system outcomes. Many of the patterns in our field’s literature formulate tried-and-true mechanism designs addressing very specific system capabilities (often internally focused at system sustaining and structural integrity concerns because these are common across systems irrespective of their specific user-facing functionality). A system has functions just like a body has functions. And many of these are internal system sustaining functions that have to do with continuity rather than serving any immediate external demand being made of the system.

Together, the expressions of the Conceptual Architecture form a conceptual framework within which we conceive of, reason about, communicate and share, extend and reify and evolve the key design ideas of the system.

References and More Information

  • Conceptual Architecture [Draft for Review], Ruth Malan
  • Conceptual Architecture and example Conceptual Architecture and Why Bother with Concepts, by Doug Newdick
  • Our draft chapter on Conceptual Architecture (the book has been reconceived and is being rewritten)
  • Key to conceptual architecture is the notion of abstraction. I need to rework it, but this piece on Software Abstractions gives an introduction.
  • Logical Architecture is the actionable set of architectural design descriptions or specifications, and includes interface specification.
  • Context: see Visual Architecting Poster and Core Activities Chart.
  • Conway’s Law and architecture of responsibility
  • The influence here also includes the RDD (responsibility driven design) work of Rebecca Wirfs-Brock, as well as work we were doing on Team Fusion under the leadership of Derek Coleman.
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