Concepts
Foundational system principles for architecture decisions.
Guiding question: Which core principle explains the behavior you observe in the system?
Adaptation
Adaptation describes how systems learn from change and adjust their behavior.
Circular Causality
Circular causality describes feedback effects rather than linear cause and effect.
Complex Adaptive Systems
Complex adaptive systems change their behavior through local adaptation and feedback among many components.
Constraints and Bottlenecks
Bottlenecks limit the overall performance of the system and determine where improvements actually matter.
Conway's Law
Organizations that design systems are forced to create designs that mirror the communication structures of those organizations.
Delays
Delays exist in every system. They distort our perception of cause and effect and push us toward drastic overreactions.
Emergence
Emergence describes global system properties that arise only through the interaction of local parts and cannot be predicted from the parts alone.
Feedback Loops
Feedback loops, whether reinforcing or balancing, are the basic building blocks that drive or stabilize system behavior over time.
Interdependence
Elements in a system depend on one another; you cannot change one part in isolation without influencing the whole.
Leverage
Leverage refers to points in a system where small, well-placed interventions create deep and lasting effects.
Mental Models
Mental models are deeply rooted assumptions that determine which system signals we notice at all and how we make decisions.
Non Linear Effects
Nonlinear effects mean that small causes can trigger massive consequences, while huge efforts often fade without visible impact.
Open and Closed Systems
Closed systems decouple from their environment, while open systems exist in constant exchange of energy and information.
Policy Resistance
Complex systems often contain a built-in defensive force that counters and blocks even well-intended solution attempts.
Purpose and Function
Every system has an objective purpose or function that can be read from its actual behavior, not from its official slogan.
Requisite Variety
Ashby's Law of Requisite Variety says that only variety can absorb variety. To control a complex system, the control system needs at least as many response options as the system it is trying to govern.
Resilience
Resilience is the ability of a system not only to survive destructive shocks from outside, but to recover while preserving its structure.
Self-Organization
Self-organization is the remarkable property of complex systems to produce structures, patterns, and learning processes without central blueprints or control instances.
Sociotechnical Architecture
Software architecture can never be viewed independently from the people and teams who create and operate it.
System Boundaries
System boundaries are purely mental lines that we draw to separate what belongs to our architecture from what supposedly lies outside our control.
Systems Thinking in the Architecture Context
Systems thinking analyzes the interdependencies, feedback loops, and delays among individual parts instead of trying to repair them in isolation.
Top-Down vs. Bottom-Up Architecture
Navigating between hard centralized top-down architecture guidelines and the local bottom-up evolution of teams.