!!! Overview
These show some [{$pagename}] that are specific to [LDAP Server Implementations] that we have discovered.!! [Microsoft Active Directory] [1]
Active Directory supports the approxMatch filter clause of [RFC 2251] section 4.5.1. However, it is implemented identically to equalityMatch; for example, the filter is true if the values are equal. __No approximation is performed__. Filter clauses of the form "(X=Y)" and "(X~=Y)" may be freely substituted for each other.

Active Directory in Windows 2000 operating system __does not__ implement three-value logic for search filter evaluation as defined in [RFC 2251] section 4.5.1. In Windows 2000, filters evaluate to either "true" or "false". Filters that would evaluate to "Undefined", as per the RFC, are instead evaluated to "false". 

However, Active Directory in Windows Server 2003 operating system, Windows Server 2008 operating system, Windows Server 2008 R2 operating system, Windows Server 2012 operating system, and Windows Server 2012 R2 operating system uses three-value logic for evaluating search filters, in conformance with the RFC.

Active Directory does not support [constructed attributes|Virtual Attribute][2] in search filters. When a search operation is performed with such a search filter, Active Directory fails with inappropriateMatching as defined in [RFC 2251] section 4.1.10.

! [Extensible Match]
Active Directory does not support the[Extensible Match] rules defined in [RFC 2252] section 8, [RFC 2256] section 8, and [RFC 2798] section 9. 

Active Directory only exposes [Microsoft Active Directory Extensible Match Rules]. Other than these rules, the rules that are used for comparing values (for example, comparing two String(Unicode) attributes for equality or ordering) are not exposed as extensible match rules. !! More Information
There might be more information for this subject on one of the following:
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* [#1] - [3.1.1.3.1.3.1 Search Filters|http://msdn.microsoft.com/en-us/library/cc223241.aspx|target='_blank'] - based on information observed on 2014-09-04 
* [#2] - [3.1.1.4.5 Constructed Attributes|http://msdn.microsoft.com/en-us/library/cc223384.aspx|target='_blank'] - based on information observed on 2014-09-04