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Oracle® Text Reference
11g Release 2 (11.2)

Part Number E16593-02
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D Oracle Text Multilingual Features

This Appendix describes the multilingual 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 multilingual indexing features:

D.2.1 Multilingual Features for Text Index Types

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

See Also:

"Lexer Types" for a description of available lexers

D.2.1.1 CONTEXT Index Type

The CONTEXT index type fully supports multilingual features, including use of the language and character set columns. The following lexers are supported:

  • AUTO_LEXER

  • MULTI_LEXER

  • USER_LEXER

  • WORLD_LEXER

CONTEXT also supports use of all Chinese, Japanese, and Korean language lexers as follows:

  • CHINESE_LEXER

  • CHINESE_VGRAM_LEXER

  • JAPANESE_LEXER

  • JAPANESE_VGRAM_LEXER

  • KOREAN_MORPH_LEXER

D.2.1.2 CTXCAT Index Type

CTXCAT supports the multilingual features of the BASIC_LEXER with the exception of indexing themes, and supports the following additional lexers:

  • AUTO_LEXER

  • USER_LEXER

  • WORLD_LEXER

CTXCAT also supports the following lexers:

  • CHINESE_LEXER

  • CHINESE_VGRAM_LEXER

  • JAPANESE_LEXER

  • JAPANESE_VGRAM_LEXER

  • KOREAN_MORPH_LEXER

D.2.1.3 CTXRULE Index Type

The CTXRULE index type supports the multilingual features of the BASIC_LEXER including ABOUT and STEM operators. It also supports Japanese, Chinese, and Korean (when used with the SVM_CLASSIFIER).

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. Table D-1 describes the supported lexers.

Table D-1 Oracle Text Lexer Types

Lexer Supported Languages

AUTO_LEXER

Lexer for indexing columns that contain documents of different 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_MORPH_LEXER

Lexer for extracting tokens from Korean text.

USER_LEXER

Lexer you create to index a particular language.

WORLD_LEXER

Lexer for indexing tables containing documents of different languages; autodetects languages in a document


D.2.3 Auto Lexer Features

AUTO_LEXER automatically detects document language, and performs language identification, word segmentation, and stemming. The AUTO_LEXER also enables customization of these components.

See Also:

"AUTO_LEXER"

D.2.4 Basic Lexer Features

The following features are supported with the BASIC_LEXER preference. 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.2.4.1 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.2.4.2 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.2.4.3 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.2.4.4 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.2.4.5 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. Specifying index stems enables better query performance for stem queries, for example $computed.

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

D.2.5 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. 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.2.6 World Lexer Features

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

WORLD_LEXER processes all database character sets and supports the Unicode 5.0 standard. For WORLD_LEXER to be effective with documents that use multiple languages, AL32UTF-8 or UTF8 Oracle character set encoding must be specified. This includes supplementary, or "surrogate-pair," characters.

Table D-2 and Table D-3 show the languages supported by WORLD_LEXER. This list may change as the Unicode standard changes, and in any case should not be considered exhaustive. (Languages are grouped by Unicode writing system, not by natural language groupings.)

Table D-2 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, Nepali, Pali, Sanskrit

Ethiopic

Amharic, Ge'ez, Tigrinya, Tigre

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-3 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-4 shows languages not supported by the World Lexer.

Table D-4 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

Ogham

Ogham

Runic

Runic

Tai Le (Tai Lu, Lue, Dai Le)

Tai Le

Ugaritic

Ugaritic

Yi

Yi

Yi Jang Hexagram

Yi Jang


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, French, German, Italian, Dutch, Spanish, Portuguese, Japanese, Optical Character recognition (OCR), and automatic language detection.

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. Appendix E, "Oracle Text Supplied Stoplists", lists the stoplists for various languges.

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

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 Multilingual Features Matrix

The following table summarizes the multilingual features for the supported languages. Note that the Auto Detect column lists languages that can be automatically detected by AUTO_LEXER.

Table D-5 Multilingual Features for Supported Languages

LANGUAGE AUTO DETECT ALTERNATE SPELLING FUZZY MATCHING LANGUAGE SPECIFIC LEXER DEFAULT STOP LIST STEMMING

ENGLISH

Yes

N/A

Yes

Yes

Yes

Yes

GERMAN

Yes

Yes

Yes

Yes

Yes

Yes

JAPANESE

Yes

N/A

Yes

Yes

No

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

PORTUGUESE

Yes

N/A

Yes

Yes

Yes

Yes

KOREAN

Yes

N/A

No

Yes

No

Yes

SIMPLIFIED CHINESE

Yes

N/A

No

Yes

Yes

Yes

TRADITIONAL CHINESE

Yes

N/A

No

Yes

Yes

Yes

DANISH

Yes

Yes

No

Yes

No

Yes

SWEDISH

Yes

Yes

No

Yes

Yes

Yes

FINNISH

Yes

N/A

No

Yes

No

Yes

ARABIC

Yes

N/A

No

Yes

No

Yes

GREEK

Yes

N/A

No

Yes

No

Yes

BOKMAL

Yes

N/A

No

Yes

No

Yes

POLISH

Yes

N/A

No

Yes

No

Yes

RUSSIAN

Yes

N/A

No

Yes

No

Yes

SLOVENIAN

Yes

N/A

No

Yes

No

Yes

THAI

Yes

N/A

No

Yes

No

Yes

CATALAN

Yes

N/A

No

Yes

No

Yes

CROATIAN

Yes

N/A

No

Yes

No

Yes

HEBREW

Yes

N/A

No

Yes

No

Yes

NYNORSK

Yes

N/A

No

Yes

No

Yes

SERBIAN

Yes

N/A

No

Yes

No

Yes

TURKISH

Yes

N/A

No

Yes

No

Yes

CZECH

Yes

N/A

No

Yes

No

Yes

HUNGARIAN

Yes

N/A

No

Yes

No

Yes

PERSIAN

Yes

N/A

No

Yes

No

Yes

SLOVAK

Yes

N/A

No

Yes

No

Yes