|Oracle® Text Reference
10g Release 2 (10.2)
|PDF · Mobi · ePub|
This Appendix describes the multi-lingual features of Oracle Text. The following topics are discussed:
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.
The following sections describe the multi-lingual indexing features.
The following sections describes the supported multilingual features for the Oracle Text index types.
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.
CTXCAT supports the multi-lingual features of the BASIC_LEXER with the exception of indexing themes.
CTXCAT also supports the following lexers:
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:
|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:
|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:
|KOREAN_MORPH_LEXER||Lexer for extracting tokens from Korean text.|
|USER_LEXER||Lexer you create to index a particular language.|
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.
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.
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.
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.
See Also:"Base-Letter Conversion"
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.
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.
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.
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-2 and Table D-3 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.)
|Language Group||Languages Include|
|Arabic||Arabic, Farsi, Kurdish, Pashto, Sindhi, Urdu|
|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|
|Hebrew||Hebrew, Ladino, Yiddish|
|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|
|Sinhalese, Sinhala||Pali, Sinhalese|
|Thaana||Dhiveli, Divehi, Maldivian|
|Language Group||Languages Include|
|Chinese||Cantonese, Mandarin, Pinyin phonograms|
|Japanese||Japanese (Hiragana, Kanji, Katakana)|
Table D-4 shows languages not supported by the World Lexer.
|Language Group||Languages Include|
|Canadian Syllabics||Blackfoot, Carrier, Cree, Dakhelh, Inuit, Inuktitut, Naskapi, Nunavik, Nunavut, Ojibwe, Sayisi, Slavey|
|Tai Le (Tai Lu, Lue, Dai Le)||Tai Le|
|Yi Jang Hexagram||Yi Jang|
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.
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.
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, Optical Character recognition (OCR), and automatic language detection.
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.
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.
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.
The following table summarizes the multilingual features for the supported languages.
|LANGUAGE||ALTERNATE SPELLING||FUZZY MATCHING||LANGUAGE SPECIFIC LEXER||DEFAULT STOP LIST||STEMMING|