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Rule-Based Classification in Data Mining


In this article, we take a look at rule-based classifiers, in which the learned model is represented as a set of IF-THEN rules. As a first step, we will investigate the ways in which such principles can be used to the process of classification.After that, we look into the many ways that they may have been created, such as by making use of a decision tree or a sequential covering approach that was applied directly to the training data. Our Data scientist course online helps you understand more about rule based classification and how it used in classifying data or objects based on a set of rules or conditions.

What is Rule-Based Classification?

Rule-based classifiers are another method for deducing a subject's categorization; these classifiers establish a subject's classification based on a set of "if" and "otherwise" rules. The creation of descriptive models normally involves utilising these various classifiers due to the fact that these criteria are easy to comprehend. If a rule is able to anticipate a certain class, we refer to that class as the rule's consequent, and the condition that is evaluated using the if keyword is the rule's antecedent. 

Classifiers that rely on rules have the following characteristics:

  • The term "coverage" is used in the field of statistics to refer to the proportion of available data that satisfies the requirements of a certain rule.
  • Rule-based classifiers will often give rules that are not mutually exclusive with one another, which means that several rules may be applicable to the same data set.
  • There is a possibility that certain records will not be covered by the rules that are generated by rule-based classifiers.
  • They result in linear decision boundaries, but because several rules can be triggered by the same record, they are oftentimes far more involved than a decision tree would be.

Knowing that the rules are not exclusive raises the question of how the class would be picked in the case that many rules, each with possibly different implications, apply to the same data. This raises the question because knowing that the rules are not exclusive raises the question.

The problem described above has two different possible solutions:

1) Both of the rules can be rated, with the rule that has the greatest ranking being the one that decides which class is ultimately appropriate.

2) Even if the criteria aren't organised, we may still distribute votes for each category according to how important they are in comparison to the others.

Using IF-THEN Rules for Classification

Rules are a good way of representing information or bits of knowledge. A rule-based classifier uses a set of IF-THEN rules for classification. An IF-THEN rule is an expression of the form IF condition THEN conclusion.

 An example is rule R1,

 R1: IF age = youth AND student = yes THEN buys computer = yes.

 The “IF”-part (or left-hand side) of a rule is known as the rule antecedent orprecondition. The “THEN”-part (or right-hand side) is the rule consequent. In the rule antecedent, the condition consists of one or more attribute tests (such as age = youth, and student = yes) that are logically ANDed. The rule’s consequent contains a class prediction (in this case, we are predicting whether a customer will buy a computer). R1 can also be written as

 R1: (age = youth) ∧ (student = yes) ⇒ (buys computer = yes).

If the condition (that is, all of the attribute tests) in a rule antecedent holds true for a given tuple, we say that the rule antecedent issatisfied (or simply, that the rule is satisfied) and that the rule covers the tuple. A rule R can be assessed by its coverage and accuracy. Given a tuple, X, from a classlabeled data set, D, let ncovers be the number of tuples covered by R; ncorrect be the number of tuples correctly classified by R; and |D| be the number of tuples in D. We can define the coverage and accuracy of R as

                                               coverage(R) =ncoversD

                                  accuracy(R) = ncorrectncovers

Rule Extraction from a Decision Tree

To classify data, we were taught to construct a decision tree using the data used for training. Decision tree classifiers are widely used because their operation is intuitive and they consistently produce accurate results. Huge decision trees are often unintelligible. In this part, we examine the process of developing a rule-based classifier by mining a decision tree for IF-THEN rules. For very vast decision trees, the IF-THEN rules may be more intuitive to people.

Every possible branch from the root node to a leaf node must be converted into a rule before the tree can be mined for its rule set. The "IF" element of a rule is formed by logically ANDing all of the route-splitting criteria along that path. The rule's consequent ("THEN" section) is the class prediction, which is stored at the leaf node.

Rule Induction Using a Sequential Covering Algorithm

Without initially needing to create a decision tree, IF-THEN rules may be derived from the training data using a sequential covering technique. Each rule for a given class will ideally cover many of the tuples of that class (and presumably none of the tuples of other classes), thus the name "sequential learning." In this part, we'll discuss sequential covering algorithms, the most popular method for mining disjunctive sets of classification rules. Keep in mind that a more recent alternative strategy involves the use of associative classification algorithms to produce classification rules by looking for commonly occurring attribute-value combinations. It's possible that these two things will link together to generate rules that can be utilised for categorization after being studied. Because this later method relies on association rule mining, A wide variety of sequential covering algorithms exist. Variants such as AQ, CN2, and even the more modern RIPPER, have found widespread popularity. This is the overarching plan of attack. Each rule is learnt individually. As soon as a new rule is learnt, the tuples that fall inside its scope are dropped, and the procedure is repeated with the remaining tuples. In contrast to decision tree induction, this sequential learning of rules is more efficient. The induction of a decision tree may be thought of as learning a set of rules all at once, as the path to each leaf in the tree represents a rule.

Each section of the school's regulations is taught separately. If we are trying to learn a rule for class Ci, then ideally that rule would apply to all (or most) of the training tuples in class C and none (or few) of the tuples in other classes. The taught rules should be quite precise in this way. Rule coverage is not need to be comprehensive.


Sequential covering. Learn a set of IF-THEN rules for classification.
Input: D, a data set class-labeled tuples; 
Att vals, the set of all attributes and their possible values.

 Output: A set of IF-THEN rules.

Method: (1) Rule set = {}; // initial set of rules learned is empty

                   (2) for each class c do 

                   (3) repeat 

                   (4) Rule = Learn One Rule(D, Att vals, c);

                   (5) remove tuples covered by Rule from D;

                   (6) until terminating condition;

                   (7) Rule set = Rule set +Rule; // add new rule to rule set

                   (8) endfor

                   (9) return Rule Set;

Evaluation Criteria for Rules

Learn The quality of rules in One Rule should be quantified. Each time an attribute test is being considered, the rule's condition is evaluated to determine if it can be made better by adding the test.

Rule Pruning

When analysing rules, Rule Pruning Learn One Rule does not employ a test set. The initial training tuples are utilised in order to carry out the procedures for assessing the quality of rules, as described previously.

This evaluation has a favourable outcome due to the fact that the rules will most likely overfit the data. That is to say, the rules could perform very well on the data that they were trained on, but they might perform less well on future data. We may make amends for this situation by relaxing the rules and regulations. "Pruning" is the term used to describe the process of removing a conjunct from a rule (attribute test). We make the decision to prune a rule, denoted by R, if an external collection of tuples reveals that the rule's quality has increased as a result of having been pruned. In the same way that decision tree pruning does, the term "pruning set" is also employed. There are many other approaches to pruning, and the pessimistic pruning technique was only one illustration of one conceivable approach. The method that FOIL uses is uncomplicated while still producing very good results. In the event that we have a rule R,

                                          FOIL Prune(R)=pos -negpos+neg

where pos represents the number of tuples that R covers that are positive and neg represents the number of tuples that R covers that are negative. If R is able to improve its performance on a pruning set, then the value of this number will rise. As a result, we make reductions to R if the version that has been pruned has a higher FOIL Prune value. When thinking about pruning, RIPPER will often look to the conjunct that was most recently introduced as the starting point.

Conjuncts are eliminated one at a time so long as doing so produces an improvement in the situation.

Application of Rule Based Classification

  • Credit Scoring: Rule-based classifiers can be used to assess creditworthiness of individuals or businesses by analyzing factors such as income, credit history, and debt-to-income ratio.
  • Predictive Maintenance: By analyzing equipment data, rule-based systems can predict when maintenance is needed before a breakdown occurs, reducing downtime and improving efficiency
  • Spam Filtering: Rule-based classifiers are commonly used in email filters to detect and block unwanted spam messages based on certain criteria such as keywords or sender information.
  • Quality Control: In manufacturing settings, rule-based systems can analyze product quality data to identify defects and improve production processes.

For example- In the healthcare industry, rule-based classifiers have been successfully applied for disease diagnosis. In one study conducted at a hospital in China, a rule-based classifier was developed using patient symptoms and medical history to diagnose liver diseases with high accuracy. The system was able to correctly diagnose over 90% of cases compared to traditional diagnostic methods which had an accuracy rate of around 70%.

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In the finance industry- Rule-based classifiers have been widely adopted for fraud detection. For instance, credit card companies use these systems to monitor transactions for unusual activity patterns that may indicate fraudulent behavior. When suspicious activities are detected by the system based on preset rules (such as large purchases made from foreign countries), alerts are sent out so that further investigation can take place.

Overall, applications of rule-based classifiers are diverse and continue to expand across various industries due their effectiveness in automating decision-making processes while ensuring accuracy and consistency.

Benefits of Using a Rule-Based Classifier

There are several advantages associated with using a rule-based classifier:

1) Transparency - Since each decision made by a rule-base classifier follows pre-defined logic; it's easy for users/analysts/data scientists involved in decision-making processes to understand why certain classifications were made.

2) Accuracy - When properly trained with relevant datasets; rule base classifiers tend towards high accuracy levels due to their ability to learn complex relationships between variables/features present in those datasets.

3) Flexibility - Rules can easily be modified when necessary without requiring significant changes in underlying algorithms thus providing greater flexibility than other methods such as neural networks where changing even small aspects might require retraining entire models again from scratch

4) Interpretability - Because each decision made by these systems follows pre-defined logic; it’s easier for analysts/data scientists involved in decision-making processes to understand why certain classifications were made.

5) Scalability - Rule-based classifiers can be scaled up to handle large datasets with ease. This is because they operate on a set of pre-defined rules that do not change regardless of the size or complexity of the dataset.

6) Explainability - The ability to explain how decisions were made by a rule-based classifier makes it an ideal tool for regulatory compliance, especially in industries such as finance and healthcare where transparency is crucial.

7) Speed - Rule-based classifiers are generally faster than other machine learning algorithms as they rely on pre-defined rules rather than complex mathematical models, making them ideal for real-time applications.


Rules-Based Classification provides valuable insights into large amounts of structured/unstructured data allowing organizations to make informed decisions faster while reducing costs associated with manual processing. It also offers transparency, flexibility, and interpretability thereby increasing trustworthiness among stakeholders. This technology continues evolving rapidly so expect a continued growth adoption rate especially given the potential benefits offered compared to traditional machine learning techniques like neural networks. You can check out our resume sample writing guide to amp up your CV that can lead to various opportunities regarding data mining. 

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