D Multilingual Features

D.2.1 Index Types

The following sections describes the supported multilingual features for the Oracle Text index types.

D.2.2 Lexer Types

Oracle Text supports the indexing of different languages by enabling you to choose a lexer in the indexing process. The lexer you employ determines the languages you can index. The following table describes the supported lexers:

D.2.3 Basic Lexer Features

The following features are supported with the BASIC_LEXER preference. You enable these features with attributes of the BASIC_LEXER. Features such as alternate spelling, composite, and base letter can be enabled together for better search results.

D.2.4 Multi Lexer Features

The MULTI_LEXER lexer enables you to index a column that contains documents of different languages. During indexing Oracle Text examines the language column and switches in the language-specific lexer to process the document. You define the lexer preferences for each language before indexing.

The multi lexer enables you to set different preferences for languages.For example, you can have composite set to TRUE for German documents and composite set to FALSE for Dutch documents.

D.2.5 World Lexer Features

Like MULTI_LEXER, the WORLD_LEXER lexer enables you to index documents that contain different languages; however, it automatically detects the languages of a document and so does not require you to create a language column in the base table.

WORLD_LEXER processes most languages whose characters are defined as part of Unicode 4.0. For WORLD_LEXER to be effective, documents with multiple languages must use AL32UTF-8 or UTF8 Oracle character set encoding (including supplementary, or "surrogate-pair," characters).

Table D-1 and Table D-2 show the languages supported by WORLD_LEXER. Note: this list may change as the Unicode standard changes, and in any case should not be considered exhaustive. (Languages are group by Unicode writing system, not by natural language groupings.)

Table D-3 shows languages not supported by the World Lexer.

D.3.1 ABOUT Operator

Use the ABOUT operator to query on concepts. The system looks up concept information in the theme component of the index.

This feature is supported for English and French with CONTEXT indexes only.

D.3.2 Fuzzy Operator

This operator enables you to search for words that have similar spelling to specified word. Oracle Text supports fuzzy for English, German, Italian, Dutch, Spanish,, Japanese, and Optical Character recognition (OCR).

D.3.3 Stem Operator

This operator enables you to search for words that have the same root as the specified term. For example, a stem of $sing expands into a query on the words sang, sung, sing. The Oracle Text stemmer supports the following languages: English, French, Spanish, Italian, German, Japanese and Dutch.

D.5.1 Knowledge Base Extension

You can extend theme functionality to languages other than English or French by loading your own knowledge base for any single byte white space delimited language, including Spanish.