Forward And Backward Chaining: An Overview In 4 Easy Points


Forward and backward chaining is techniques for reasoning that exist in the Expert System Domain of AI. These methods are utilized in expert systems like DENDRAL and MYCIN to create answers for genuine issues.

Forward and backward chaining both applies the Modus ponens inference rule.

Inference engine

An inference engine in artificial intelligence is utilized as a part of the framework to derive new data from a knowledge base utilizing reasoning and logical rules. The first-since forever inference engines were a part of expert systems in artificial intelligence.

As recently expressed, an inference engine in artificial intelligence foresees results with the generally existing pool of data, comprehensively examining it and utilizing logical reasoning to anticipate the results.

Inference engine in artificial intelligence works in one of the two different ways:

  1. Forward chaining
  2. Backward chaining

In this article let us look at:

  1. Forward Chaining
  2. Backward Chaining
  3. Advantages and Disadvantages of Forward and Backward Chaining
  4. Forward Chaining vs Backward Chaining

1. Forward chaining

Forward chaining is a technique for reasoning in AI where inference rules are applied to existing information to remove extra information until an objective is accomplished. 

In Forward chaining, the inference engine turns over by assessing existing conditions, derivations, and facts before reasoning new data. An objective is accomplished through the control of knowledge that exists in the knowledge base.

It can be utilized in interpreting, controlling, monitoring, and planning applications. 

Properties of Forward Chaining:

  • It is a down-up approach, as it moves from base to top.
  • It is generally utilized in the expert framework, like production, business, and CLIPS rule frameworks.

Forward chaining example:

A straightforward forward chaining example can be clarified in the accompanying grouping. 

  • Y
  • Y à Z
  • Z


  • Y is the beginning stage.
  • Y à Z addresses a fact
  • This fact is utilized to accomplish a decision Z.

A practical example will go as follows;

  • John is running (Y)
  • If an individual is running, he will sweat (Y à Z)
  • Consequently, John is sweating (Z)

2. Backward chaining

Backward chaining is an idea in AI that includes backtracking from the endpoint or objective to steps that prompted the endpoint. Backward chaining beginnings from the objective and moves in backwards to grasp the steps that were taken to accomplish this objective.

The backtracking cycle can likewise empower an individual to build up logical steps that can be utilized to discover other significant arrangements. 

It can be utilized in prescription, diagnostics, and debugging applications. 

Properties of Backward Chaining: 

  • It is recognised as a top-down approach.
  • It is utilized in proof assistants, inference engines, automated theorem proving tools, game theory, and different artificial intelligence applications.

Backward chaining example:

The data gave in the earlier example can be utilized to give a basic clarification of backward chaining. It can be clarified in the accompanying succession:

  • Z
  • Y à Z
  • Y


  • Z is the endpoint or goal, that is utilized as the beginning stage for the backward chaining.
  • Y à Z is a reality that should be stated to show up at the endpoint Z.
  • Y is the initial state.

A practical example will go as follows;

  • John is sweating (Z)
  • If an individual is running, he will sweat (Y à Z)
  • John is running (Y)

3. Advantages and disadvantages of forward and backward chaining

Advantages of forward chaining:

  • It’s more adaptable than backward chaining since it doesn’t have a limit on the information got from it.
  • It gives a decent premise to come to conclusions.
  • It very well may be utilized to reach numerous conclusions.

Advantages of backward chaining:

  • In this kind of chaining, the right arrangements can be inferred successfully if pre-decided principles are met by the inference engine.
  • It’s a faster strategy for thinking than forward chaining because the endpoint is accessible.
  • The outcome is as of now known, which makes it simple to deduce inferences.

Disadvantages of forward chaining:

  • Not at all like in backward chaining, the clarification of observations or facts for this kind of chaining isn’t clear.
  • The interaction of forward chaining might be tedious.
  • It might require some time to synchronize and eliminate accessible information.

Disadvantages of backward chaining:

  • It just infers information that is required, which makes it less adaptable than forward chaining.
  • It doesn’t conclude with numerous answers or solutions.
  • The way toward reasoning can begin if the endpoint is known.

4. Forward chaining vs backward chaining

  • Forward chaining is a bottom-up approach, while backward chaining is a top-down approach.
  • Forward and backward chaining uses breadth-first search and depth-first search strategy respectively.
  • Forward chaining is operated in the forward direction, while backward chaining operated in the backward direction.
  • Forward and backward chaining is known as data-driven and goal-driven respectively.


Forward and backward reasoning is significant strategies in AI or artificial intelligence. These ideas contrast essentially as far as operational direction, speed, technique, strategy, and approach.Forward and backward chaining is like an exhaustive search and unnecessary path of reasoning respectively.

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