Overview of Alternative Spelling Features

Some languages have alternative spelling forms for certain words. For example, the German word Schoen can also be spelled as Schön.

The form of a word is either original or normalized. The original form of the word is how it appears in the source document. The normalized form is how it is transformed, if it is transformed at all. Depending on the word being indexed and which system preferences are in effect (these are discussed in this chapter), the normalized form of a word may be the same as the original form. Also, the normalized form may comprise more than one spelling. For example, the normalized form of Schoen is both Schoen and Schön.

Oracle Text handles indexing of alternative word forms in the following ways:

• Alternate Spelling—indexing of alternative forms is enabled

• Base-Letter Conversion—accented letters are transformed into non-accented representations

• New German Spelling—reformed German spelling is accepted

Enable these features by specifying the appropriate attribute to the BASIC_LEXER. For instance, enable alternate spelling by specifying either GERMAN, DANISH, or SWEDISH for the ALTERNATE_SPELLING attribute. As an example, here is how to enable alternate spelling in German:

begin
ctx_ddl.create_preference('GERMAN_LEX', 'BASIC_LEXER');
ctx_ddl.set_attribute('GERMAN_LEX', 'ALTERNATE_SPELLING', 'GERMAN');
end;

To disable alternate spelling, use the CTX_DDL.UNSET_ATTRIBUTE procedure as follows:

begin
ctx_ddl.unset_attribute('GERMAN_LEX', 'ALTERNATE_SPELLING');
end;

Oracle Text converts query terms to their normalized forms before lookup. As a result, users can query words with either spelling. If Schoen has been indexed as both Schoen and Schön, a query with Schön returns documents containing either form.

This section contains the following topics.

• Alternate Spelling

• Base-Letter Conversion

• New German Spelling