Difference Between Backward Chaining and Forward Chaining

Backward chaining and forward chaining are two typical reasoning techniques used in artificial intelligence and logic programming to arrive at a goal by moving backward or ahead through a list of rules or conditions. While each strategy has benefits and drawbacks, developers and researchers must be able to distinguish between them in order to select the way that is best suited to solving a particular issue.

Read this article to understand the major distinctions between backward chaining and forward chaining, as well as their benefits and drawbacks. We will also discuss how they are applied in various situations.

What is Backward Chaining?

In logic programming and artificial intelligence, the technique of "backward chaining" is used to get from the objective to the assumptions or circumstances that support it.

Backward chaining starts with a hypothesis or objective and works backward through a set of circumstances or rules to see if the goal is supported by those conditions. The system verifies each requirement until it reaches a point where all requirements are met or until it reaches a requirement that cannot be met, at which time the system terminates and communicates the outcome.

Backward chaining, for instance, could be employed in a medical diagnosis system to identify the primary reason behind a group of symptoms. In order to identify the diseases or disorders that might be producing such symptoms, the system starts with the symptoms as the goal and works backward through a series of criteria and conditions.

Advantages of Backward Chaining

  • Effective use of resources − Backward chaining is a method of problem-solving that is effective because it only investigates the pertinent laws or conditions required to achieve a goal. Compared to alternative methods, this can save time and computational resources.

  • Goal oriented − Backward chaining is goal-oriented in that it starts with a predetermined objective and works backward to identify the pertinent circumstances or regulations that support it.

  • Flexible − Backward chaining is adaptable since it is simple to configure for many applications and has a wide range of problem-solving capabilities.

Disadvantages of Backward Chaining

  • Restricted reasoning − Backward chaining only works in one direction and might not be able to produce fresh insights or solutions that weren't specifically coded into the system.

  • Incomplete search − Backward chaining occasionally generates partial findings or fails to fully investigate all potential solutions.

  • Handling conflicts − Conflict resolution may be challenging when using backward chaining to reconcile inconsistencies or conflicts between several laws or facts.

What is Forward Chaining?

By starting with the premises or conditions and applying them one at a time to arrive at a conclusion, forward chaining is a reasoning technique used in artificial intelligence and logic programming.

By applying a set of rules to an initial set of facts or circumstances, the system can then generate new facts or conditions. This process is known as forward chaining. The system keeps using these rules and producing new facts until it reaches a conclusion or a goal.

For instance, forward chaining might be employed in a rule-based system for diagnosing automobile issues to identify a specific problem with the vehicle. Starting with observations of the car's behaviour, the system would employ a set of rules to create potential reasons of the issue. As it narrows the options and keeps applying the rules to rule out unlikely explanations, the system eventually comes to a conclusion about the issue.

Advantages of Forward Chaining

  • Efficiency − Forward chaining is a method of problem-solving that is effective because it draws on previously established facts or circumstances in order to arrive at a solution. Compared to alternative methods, this can save time and computational resources.

  • Flexibility − Forward chaining is adaptable because it can handle a variety of problem kinds and is simple to modify for various purposes.

  • Real-time decision making − Because forward chaining can produce a conclusion fast based on a set of facts or circumstances, it is appropriate for real-time decision making.

Disadvantages of Forward Chaining

Incomplete search: In some circumstances, forward chaining may not fully investigate all potential solutions or may produce partial results.

Absence of a global perspective: As forward chaining simply takes into account the current set of facts or circumstances, it might not evaluate the problem's wider context, which could result in inaccurate conclusions.

Difficulty in handling conflicts: Conflict resolution may be challenging with forward chaining when there are inconsistencies or conflicts between several facts or rules.

Difference Between Forward Chaining and Backward Chaining

The following table highlights the major differences between Forward Chaining and Backward Chaining −

Forward Chaining

Backward Chaining

Forward chaining begins with known facts and uses the inference rule to extract new information as it advances towards the objective.

In order to identify the necessary facts to support the aim, backward chaining starts with the goal and moves backward through the inference rules.

It follows a bottom-up strategy.

It uses a top-down strategy.

As we arrive at the target using the data at hand, forward chaining is referred to as a data-driven inference strategy.

As we begin with the objective and break it down into sub-goals to extract the facts, backward chaining is regarded as a goal-driven technique.

An approach known as "breadth-first search" is used in forward chaining reasoning.

A depth-first search methodology is used in backward chaining reasoning.

For all the available rules, forward chaining tests

Backward chaining only checks a small set of necessary rules.

The planning, monitoring, control, and interpretation applications benefit from forward chaining.

For use in diagnosing, prescribing, and troubleshooting, backward chaining is appropriate.

There are an endless number of outcomes that can be produced via forward chaining.

There are a limited number of outcomes that can be reached by backward chaining.

It moves in the direction of forward motion.

It functions in the opposite direction.

Any conclusion is the goal of forward chaining.

The needed data is the only target of backward chaining.


In conclusion, logic programming and artificial intelligence use two different reasoning techniques called backward chaining and forward chaining. While both approaches can be helpful for delving into complicated issues and methodically approaching them, each has merits and drawbacks.

Forward chaining is adaptable and efficient, but backward chaining is goal-oriented and effective. Forward chaining, on the other hand, can lack a global viewpoint and struggle to resolve disputes, while backward chaining might have restricted reasoning and be computationally expensive.

The specific challenge and its requirements will determine which of these two approaches should be used. We can select the best approach to handle the current issue by comprehending the distinctions between these two approaches.

Updated on: 19-Apr-2023

2K+ Views

Kickstart Your Career

Get certified by completing the course

Get Started