Library › Information Technology 9626 › Chaining

AS Level · Information Technology 9626

Chaining

Revise Chaining for Information Technology 9626 (AS Level) — revision notes, 22 practice questions and instant AI marking.

📖 Revision notes · preview

CHAPTER OVERVIEW

Two Ways the Inference Engine Reasons

The inference engine reasons in two fundamentally different ways. Backward chaining starts with a goal and works backwards to prove it. Forward chaining starts with facts and works forward to reach a conclusion. Neither is "right"—the choice depends on the problem.

You understand backward chaining (goal-driven) and can trace through steps

You understand forward chaining (data-driven) and can trace through steps

You know when to use each method and their real-world applications

Why This Matters

This is a concept-heavy chapter. Exams ask you to trace through both methods and explain which is better for different scenarios. The Edwina the zebra example is THE textbook example—you need to be able to work through it both ways.

Typical exam questions:

"Explain what is meant by forward chaining" (3 marks)
"Explain what is meant by backward chaining" (3 marks)
Trace a problem using either method

Key insight: The "words" matter. Backward = goal, forward = facts. That's the entire distinction.

Chapter Map

Key Definitions

⚙️ HOW RULES WORK

All expert system rules follow the IF...THEN structure:

IF [premise/condition] THEN [conclusion]

Premise (IF part): The condition we're supposing could be true. What we need to check/prove.

Conclusion (THEN part): What we get if the premise is true. The result we're trying to reach.

🎯 BACKWARD CHAINING (Goal-Driven)

Starts with: A goal or assertion to prove

Direction: Works BACKWARDS from goal to facts

Method: Finds rules where THEN matches goal, then tries to prove IF

Stops when: Facts match the IF conditions

📊 FORWARD CHAINING (Data-Driven)

Starts with: Known facts/data

Direction: Works FORWARD from facts to goal

Method: Finds rules where IF matches facts, adds THEN as new facts

Stops when: Goal/conclusion is reached

Quick Check

What is the "premise" part of an IF...THEN rule?

The textbook calls it "the part that begins with IF... what we are supposing could be true."

Backward Chaining (Goal-Driven)

🎯 The Big Idea

Start with the goal you want to prove. Work backwards through the rules, trying to prove the conditions (IF parts) that lead to that goal. Stop when you reach known facts.

📖 The Edwina Example

Scenario: A zoo receives an enclosed animal from Africa. We know:

Fact 1: Edwina has hooves
Fact 2: Edwina can run fast

Goal: Prove: "Edwina has a striped coat"

Rules we have:

Rule 1: IF X has hooves AND can run fast, THEN X is a zebra
Rule 3: IF X is a zebra, THEN X has a striped coat

Aspect

🔓 Read the full Chaining note → You're seeing the preview · sign in to read it all

Also in the full note

Forward Chaining (Data-Driven)
When to Use Each Method
Real-World Applications
Side-by-Side Comparison
Exam Checklist

What's inside

📖 Revision notes ◉ 22 practice questions 🎯 Learn mode ✦ AI flashcards ✓ Instant AI marking 🧊 3D explorers 🧪 Experiments & simulations 📈 Progress tracking

Past papers that test Chaining

Real Information Technology 9626 papers with questions on this topic — open one and get it marked instantly, free.

9626 Nov 2025 · Paper 1 · Variant 2 Cambridge · mark scheme Open → 9626 Nov 2025 · Paper 2 · Variant 2 Cambridge · mark scheme Open → 9626 Jun 2025 · Paper 1 · Variant 3 Cambridge · mark scheme Open → 9626 Nov 2024 · Paper 1 · Variant 3 Cambridge · mark scheme Open → 9626 Jun 2024 · Paper 1 · Variant 3 Cambridge · mark scheme Open → 9626 Nov 2023 · Paper 1 · Variant 1 Cambridge · mark scheme Open →

All Information Technology 9626 past papers →

Read the full Chaining notes free

That's the preview — create a free account to read the rest, plus flashcards and 22 practice questions with instant AI marking. No credit card.

Unlock the full notes free →