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Oracle® Text Reference
10g Release 1 (10.1)

Part Number B10730-01
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D Multilingual Features

This Appendix describes the multi-lingual features of Oracle Text. The following topics are discussed:

D.1 Introduction

This appendix summarizes the main multilingual features for Oracle Text.

For a complete list of Oracle Globalization Support languages and character set support, refer to the Oracle Database Globalization Support Guide.

D.2 Indexing

The following sections describe the multi-lingual indexing features.

D.2.1 Index Types

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

D.2.1.1 CONTEXT Index Type

The CONTEXT index type fully supports multi-lingual features including use of the language and character set columns, use of the MULTI_LEXER, and use of all Chinese, Japanese, and Korean language lexers.

D.2.1.2 CTXCAT Index Type

CTXCAT supports the multi-lingual features of the BASIC_LEXER with the exception of indexing themes.

CTXCAT also supports the following lexers:







D.2.1.3 CTXRULE Index Type

The CTXRULE index type supports the multi-lingual features of the BASIC_LEXER including ABOUT and STEM operators. It also supports Japanese, Chinese, and Korean.

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:

Lexer Supported Languages
BASIC_LEXER English and most western European languages that use white space delimited words.
MULTI_LEXER Lexer for indexing tables containing documents of different languages such as English, German, and Japanese.
CHINESE_VGRAM Lexer for extracting tokens from Chinese text.
CHINESE_LEXER Lexer for extracting tokens from Chinese text. This lexer offers the following benefits over the CHINESE_VGRAM lexer:
  • generates a smaller index

  • better query response time

  • generates real world tokens resulting in better query precision

  • supports stop words

JAPANESE_VGRAM Lexer for extracting tokens from Japanese text.
JAPANESE_LEXER Lexer for extracting tokens from Japanese text. This lexer offers the following advantages over the JAPANESE_VGRAM lexer:
  • generates smaller index

  • better query response time

  • generates real world tokens resulting in better precision

KOREAN_LEXER Lexer for extracting tokens from Korean text.
KOREAN_MORPH_LEXER Lexer for extracting tokens from Korean text. This lexer offers the following benefits over the KOREAN_LEXER:
  • better morphological analysis of Korean text

  • faster indexing

  • smaller indexes

  • more accurate query searching

USER_LEXER Lexer you create to index a particular language.

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.2.3.1 Theme Indexing

Enables the indexing and subsequent querying of document concepts with the ABOUT operator with CONTEXT index types. These concepts are derived from the Oracle Text knowledge base. This feature is supported for English and French.

This feature is not supported with CTXCAT index types.

D.2.3.2 Alternate Spelling

This feature enables you to search on alternate spellings of words. For example, with alternate spelling enabled in German, a query on gross returns documents that contain groß and gross.

This feature is supported in German, Danish, and Swedish.

Additionally, German can be indexed according to both traditional and reformed spelling conventions.

D.2.3.3 Base Letter Conversion

This feature enables you to query words with or without diacritical marks such as tildes, accents, and umlauts. For example, with a Spanish base-letter index, a query of energia matches documents containing both energía and energia.

This feature is supported for English and all other supported whitespace delimited languages. In English and French, you can use the basic lexer to enable theme indexing.

D.2.3.4 Composite

This feature enables you to search on words that contain the specified term as a sub-composite. You must use the stem ($) operator. This feature is supported for German and Dutch.

For example, in German, a query of $register finds documents that contain Bruttoregistertonne and Registertonne.

D.2.3.5 Index stems

This feature enables you to specify a stemmer for stem indexing. Tokens are stemmed to a single base form at index time in addition to the normal forms. Indexing stems enables better query performance for stem queries, such as $computed.

This feature is supported for English, Dutch, French, German, Italian, Spanish.

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-1 Languages Supported by the World Lexer (Space-separated)

Language Group Languages Include
Arabic Arabic, Farsi, Kurdish, Pashto, Sindhi, Urdu
Armenian Armenian
Bengali Assamese, Bengali
Bopomofo Hakka Chinese, Minnan Chinese
Cyrillic Over 50 languages, including Belorussian, Bulgarian, Macedonian, Moldavian, Russian, Serbian, Serbo-Croatian, Ukrainian
Devenagari Bhojpuri, Bihari, Hindi, Kashmiri, Marathi, Napali, Pali, Sanskrit
Ethiopic Amharic, Ge'ez, Tigrinya, Tirgre
Georgian Georgian
Greek Greek
Gujarati Gujarati, Kacchi
Gurmukhi {Punjabi
Hebrew Hebrew, Ladino, Yiddish
Kaganga Redjang
Kannada Kanarese, Kannada
Korean Korean, Hanja Hangul
Latin Afrikaans, Albanian, Basque, Breton, Catalan, Croatian, Czech, Danish, Dutch, English, Esperanto, Estonian, Faeroese, Fijian, Finnish, Flemish, French, Frisian, German, Hawaiian, Hungarian, Icelandic, Indonesian, Irish, Italian, Lappish, Classic Latin, Latvian, Lithuanian, Malay, Maltese, Pinyin Mandarin, Maori, Norwegian, Polish, Portuguese, Provencal, Romanian, Rumanian, Samoan, Scottish Gaelic, Slovak, Slovene, Slovenian, Sorbian, Spanish, Swahili, Swedish, Tagalog, Turkish, Vietnamese, Welsh
Malayalam Malayalam
Mongolian Mongolian
Oriya Oriya
Sinhalese, Sinhala Pali, Sinhalese
Syriac Aramaic, Syriac
Tamil Tamil
Telugu Telugu
Thaana Dhiveli, Divehi, Maldivian

Table D-2 Languages Supported by the World Lexer (Non-space-separated)

Language Group Languages Include
Chinese Cantonese, Mandarin, Pinyin phonograms
Japanese Japanese (Hiragana, Kanji, Katakana)
Khmer Cambodian, Khmer
Lao Lao
Myanmar Burmese
Thai Thai
Tibetan Dzongkha, Tibetan

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

Table D-3 Languages Not Supported by the World Lexer

Language Group Languages Include
Buhid Buhid
Canadian Syllabics Blackfoot, Carrier, Cree, Dakhelh, Inuit, Inuktitut, Naskapi, Nunavik, Nunavut, Ojibwe, Sayisi, Slavey
Cherokee Cherokee
Cypriot Cypriot
Limbu Limbu
Oghem Oghem
Runic Runic
Tai Le (Tai Lu, Lue, Dai Le) Tai Le
Ugaritic Ugaritic
Yi Yi
Yijang Hexagram Yijang

D.3 Querying

Oracle Text supports the use of different query operators. Some operators can be set to behave in accordance with your language. This section summarizes the multilingual query features for these operators.

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.4 Supplied Stop Lists

A stoplist is a list of words that do not get indexed. These are usually common words in a language such as this, that, and can in English.

Oracle Text provides a default stoplist for English, Chinese (traditional and simplified), Danish, Dutch, Finnish, French, German, Italian, Portuguese, Spanish, and Swedish.

D.5 Knowledge Base

An Oracle Text knowledge base is a hierarchical tree of concepts used for theme indexing, ABOUT queries, and deriving themes for document services.

Oracle Text supplies knowledge bases in English and French only.

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.

D.6 Multi-Lingual Features Matrix

The following table summarizes the multilingual features for the supported languages.

Table D-4 Multilingual Features for Supported Languages

ENGLISH Yes N/A Yes Yes Yes Yes
GERMAN Yes Yes Yes Yes Yes Yes
FRENCH Yes N/A Yes Yes Yes Yes
SPANISH Yes N/A Yes Yes Yes Yes
ITALIAN Yes N/A Yes Yes Yes Yes
DUTCH Yes N/A Yes Yes Yes Yes
DANISH Yes Yes No Yes No No
SWEDISH Yes Yes No Yes Yes No
FINNISH Yes N/A No Yes No No