Lesson 2: The Five Core Concepts

Learning Goals

• Learn the five core systems thinking concepts
• Understand how they apply to software architecture
• See how Sruja implements each concept

The Five Core Concepts

In this course, you'll master five fundamental systems thinking concepts:

┌─────────────────────────────────────────────┐
│           SYSTEMS THINKING 101              │
├─────────────────────────────────────────────┤
│  1. Parts & Relationships                   │
│  2. Boundaries                              │
│  3. Flows                                   │
│  4. Feedback Loops                          │
│  5. Context                                 │
└─────────────────────────────────────────────┘

1. Parts and Relationships

Definition: What the system contains and how those pieces connect.

In Sruja

import { * } from 'sruja.ai/stdlib'

Customer = person "End User"
Shop = system "Shop" {
  WebApp = container "Web Application"
  API = container "API Service"
  DB = database "Database"
}

// Relationships = how parts connect
Customer -> Shop.WebApp "Uses"
Shop.WebApp -> Shop.API "Calls"
Shop.API -> Shop.DB "Reads"

Why It Matters

• Structure: Defines what exists in your system
• Interactions: Shows how components communicate
• Coupling: Reveals dependencies between parts

2. Boundaries

Definition: What's inside the system vs. what's outside (the environment).

In Sruja

// Inside: Your system
Shop = system "Shop" {
  WebApp = container "Web App"
  API = container "API"
}

// Outside: External systems
PaymentGateway = system "Payment Service" {
  metadata { tags ["external"] }
}

// Crossing the boundary
Shop.API -> PaymentGateway "Processes payments"

Why It Matters

• Scope: What you're responsible for vs. dependencies
• Integration: How you connect with external systems
• Security: What needs to be protected
• Testing: What's in scope for your tests

3. Flows

Definition: How information, data, and actions move through the system.

In Sruja (Data Flow)

OrderFlow = scenario "Order Processing" {
  Customer -> Shop.WebApp "Submits order"
  Shop.WebApp -> Shop.API "Sends order data"
  Shop.API -> Shop.DB "Saves order"
  Shop.API -> PaymentGateway "Charges payment"
  Shop.API -> Shop.WebApp "Returns result"
  Shop.WebApp -> Customer "Shows confirmation"
}

Why It Matters

• Data lineage: Where does information come from and go?
• Process understanding: What's the sequence of actions?
• Bottlenecks: Where do things slow down?
• Error paths: What happens when something fails?

4. Feedback Loops

Definition: How actions create reactions that affect future actions.

In Sruja (Cycles)

// User feedback loop
User -> App.WebApp "Submits form"
App.WebApp -> App.API "Validates"
App.API -> App.WebApp "Returns result"
App.WebApp -> User "Shows feedback"

// System feedback loop
App.API -> App.DB "Updates inventory"
App.DB -> App.API "Notifies low stock"
App.API -> Admin "Sends alert"
Admin -> App.API "Adjusts inventory"

Why It Matters

• Reactive behavior: How systems respond to changes
• Stability: Does the system self-correct or spiral out of control?
• Adaptation: How the system learns and evolves
• Monitoring: What metrics indicate system health?

5. Context

Definition: The environment the system operates in - stakeholders, dependencies, constraints.

In Sruja

// Your system
Shop = system "Shop"

// Context: Stakeholders
Customer = person "End User"
Admin = person "Administrator"
Support = person "Customer Support"

// Context: Dependencies
PaymentGateway = system "Payment Service"
EmailService = system "Email Service"
Analytics = system "Analytics"

// Context relationships
Customer -> Shop "Uses"
Shop -> PaymentGateway "Depends on"
Shop -> EmailService "Sends notifications"
Admin -> Shop "Manages"

Why It Matters

• Stakeholders: Who cares about this system?
• Dependencies: What external systems do you rely on?
• Constraints: What limits your design choices?
• Success criteria: What does "good" look like?

How They Work Together

A complete systems thinking view combines all five:

┌──────────────────────────────────────────┐
│              CONTEXT                     │
│  Stakeholders: Users, Admins, Support    │
│  Dependencies: External APIs, Services   │
│                                          │
│    ┌────────── BOUNDARY ──────────┐     │
│    │                               │     │
│    │   PARTS ↔ RELATIONSHIPS       │     │
│    │   [User] → [App] → [DB]       │     │
│    │         ↑       ↓             │     │
│    │         └── FEEDBACK ─────┘  │     │
│    │                               │     │
│    │   FLOWS: Order, Payment      │     │
│    └───────────────────────────────┘     │
└──────────────────────────────────────────┘

Sruja Mapping Summary

Key Takeaways

1. Five concepts form the foundation: Parts/relationships, boundaries, flows, feedback loops, context
2. They interconnect: None exists in isolation
3. Sruja supports all five: Built into the language
4. Use them together: Complete architecture requires all perspectives
5. Practice makes perfect: You'll work with each in depth

Exercise

Pick a system you know well. For each concept, write one observation:

• Parts/Relationships: Name 3 components and how they connect
• Boundaries: What's inside vs. outside the system?
• Flows: What's a common data path through the system?
• Feedback Loops: Any automatic responses to user actions?
• Context: Who are the main stakeholders?

Next Lesson

In Lesson 3, we'll explore the practical benefits of systems thinking for software architecture.