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Also known as: SD Pattern, Building Block, Molecules of Structure
Reusable, small stock-flow and feedback patterns that serve as building blocks in system dynamics models.
DESCRIPTION
In system dynamics, molecules (or molecules of structure) are small, generic model fragments—such as balancing loops, delays, and stock-flow templates—that can be reused across problems. They accelerate model building and improve consistency by encapsulating common feedback structures. Molecules can be combined to form larger patterns and archetypes, supporting faster experimentation and clearer communication. They also aid education by illustrating core dynamic behaviors.
ALTERNATIVE DEFINITIONS
isee systems
Molecules of structure are small, reusable building blocks of dynamic models that capture recurring feedback and flow patterns.
Focuses on reuse of recurring feedback and flow structures in modeling.
System Dynamics Society
System dynamics uses feedback loops and stocks and flows to understand complex systems and their behavior over time.
Provides foundational context for molecules within system dynamics practice.
Wikipedia
System archetypes are generic structures that produce characteristic patterns of behavior in diverse systems.
Relates molecules to larger, canonical patterns called archetypes.
RELATED TERMS
Causal Loop Diagram Stock and Flow Diagram Feedback Loop Delays Limits to Growth Template Model Pattern Library
COMPETING TERMS
System Archetype
RELATIONS
- Broader: System Dynamics
KNOWLEDGE AREAS
Software Modeling Domain & Business Context Mathematics
TARGET AUDIENCE
Data Scientist Enterprise Architect Data Strategy Consultant Digital Transformation Manager Information Analyst
EXTERNAL SOURCES
- Wikipedia - System dynamics
- isee systems - Tutorials on molecules of structure
- System Dynamics Society - Professional association and resources for system dynamics
- Wikipedia - Overview of system archetypes patterns
TOP QUESTIONS
What is a Molecule in System Dynamics modeling?
A molecule is a small, reusable feedback or stock-flow template that captures a common dynamic pattern for reuse across models.
Category: Overview
How do Molecules differ from System Archetypes?
Molecules are smaller building blocks, while archetypes are larger, canonical patterns of system behavior.
Category: Misunderstanding
Why use Molecules in System Dynamics?
They accelerate model building, improve consistency, and help communicate feedback structures clearly.
Category: Relevancy
What is a common mistake with Molecules?
Using a molecule without validating its assumptions in the specific context can mislead results.
Category: Mistakes
How are Molecules documented and shared?
Through pattern libraries, model snippets, and tool-specific templates with usage notes and parameterization guidance.
Category: Collaboration
What’s a hot topic around Molecules?
Libraries that integrate with teaching tools and domain-specific molecules for health or supply chains are growing.
Category: Topic
How do Molecules support validation of System Dynamics models?
By making structure explicit, they enable targeted tests of known dynamic behaviors (e.g., delay-induced oscillations).
Category: Testing
Can Molecules be used outside traditional tools?
Yes, the patterns translate into general modeling environments and even code-based SD libraries.
Category: Requirements
Where to start learning Molecules for System Dynamics?
Begin with tutorials from tool vendors and the System Dynamics Society’s educational resources on feedback structures.
Category: Learning