IStemmer interface

[Indexing Service is no longer supported as of Windows XP and is unavailable for use as of Windows 8. Instead, use Windows Search for client side search and Microsoft Search Server Express for server side search.]

Provides methods for creating a language-specific stemmer. The stemmer generates inflected forms of a given word.

When to implement

Implement this interface to create a custom stemmer for a language. Indexing Service calls the methods of this interface to generate inflected forms for words identified when building an index.


The IStemmer interface inherits from the IUnknown interface. IStemmer also has these types of members:

  • Methods


The IStemmer interface has these methods.

Method Description

Generates alternative forms for a word and puts them in the WordFormSink.


Gets the license information for this IStemmer implementation.


Initializes the stemmer.



Stemmer components for Indexing Service run in the Local Security context. They should be written to manage buffers and to stack correctly. All string copies must have explicit checks to guard against buffer overruns. You should always verify the allocated size of the buffer and test the size of the data against the size of the buffer.


Minimum supported client

Windows 2000 Professional [desktop apps only]

Minimum supported server

Windows 2000 Server [desktop apps only]

End of client support

Windows 7

End of server support

Windows Server 2008 R2



See also

Implementing a Stemmer


Language Resource Samples