content/api/user-guide/4.2.1.4-matching-rules.mdtext

Title: 4.2.1.4 - MatchingRules
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# 4.2.1.4 - MatchingRules

A **MatchingRule** is used when processing search requests using **Filter**s, or a **Compare** or during **Modify** operations. An **AttributeType** defines up to 3 types of **MatchingRule**s:

* EQUALITY : for comparisons for equality
* ORDERING : for comparisons involving the <= or >= operators
* SUBSTR : for comparisons involving substrings, like '*xyz' or 'x*z'

There are a few extra parameters that are defined in the **MatchingRule** class:

* getSyntax() : gets the **Syntax** instance associated with the **MatchingRule**
* getSyntaxOid() : gets the **Syntax** OID associated with the **MatchingRule**

We also have 2 specific methods that are used to compare or normalize a value:

* getLdapComparator() : gets the **LdapComparator** to use to compare 2 values
* getNormalizer() : gets the **Normalizer** used to normalize a value

Those are convenient methods, specifically when you need to compare two values.

A **MatchingRule** instance is associated with a **LdapSyntax** and a **Normalizer** because it may need to get information about the attribute value check and normalization. It also contains a reference to the associated **LdapComparator**.