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10g Release 2 (10.2)

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14 Oracle Text Executables

This chapter discusses the executables shipped with Oracle Text. The following topics are discussed:

Thesaurus Loader (ctxload)

Use ctxload to do the following with a thesaurus:

An import file is an ASCII flat file that contains entries for synonyms, broader terms, narrower terms, or related terms which can be used to expand queries.


See Also:

For examples of import files for thesaurus importing, see "Structure of ctxload Thesaurus Import File" in Appendix C, "Text Loading Examples for Oracle Text".

Text Loading

The ctxload program no longer supports the loading of text columns. To load files to a text column in batch, Oracle recommends that you use SQL*Loader.

ctxload Syntax

ctxload -user username[/password][@sqlnet_address]
        -name object_name
        -file file_name
      
       [-thes]
       [-thescase y|n]
       [-thesdump]
       [-log file_name]
       [-trace]
       [-pk]
       [-export]
       [-update]

Mandatory Arguments

-user

Specify the user name and password of the user running ctxload.

The user name and password can be followed immediately by @sqlnet_address to permit logon to remote databases. The value for sqlnet_address is a database connect string. If the TWO_TASK environment variable is set to a remote database, you do not have to specify a value for sqlnet_address to connect to the database.

-name object_name

When you use ctxload to export/import a thesaurus, use object_name to specify the name of the thesaurus to be exported/imported.

You use object_name to identify the thesaurus in queries that use thesaurus operators.


Note:

Thesaurus name must be unique. If the name specified for the thesaurus is identical to an existing thesaurus, ctxload returns an error and does not overwrite the existing thesaurus.

When you use ctxload to update/export a text field, use object_name to specify the index associated with the text column.

-file file_name

When ctxload is used to import a thesaurus, use file_name to specify the name of the import file which contains the thesaurus entries.

When ctxload is used to export a thesaurus, use file_name to specify the name of the export file created by ctxload.


Note:

If the name specified for the thesaurus dump file is identical to an existing file, ctxload overwrites the existing file.

Optional Arguments

-thes

Import a thesaurus. Specify the source file with the -file argument. You specify the name of the thesaurus to be imported with -name.

-thescase y | n

Specify y to create a case-sensitive thesaurus with the name specified by -name and populate the thesaurus with entries from the thesaurus import file specified by -file. If -thescase is y (the thesaurus is case-sensitive), ctxload enters the terms in the thesaurus exactly as they appear in the import file.

The default for -thescase is n (case-insensitive thesaurus)


Note:

-thescase is valid for use with only the -thes argument.

-thesdump

Export a thesaurus. Specify the name of the thesaurus to be exported with the -name argument. Specify the destination file with the -file argument.

-log

Specify the name of the log file to which ctxload writes any national-language supported (Globalization Support) messages generated during processing. If you do not specify a log file name, the messages appear on the standard output.

-trace

Enables SQL statement tracing using ALTER SESSION SET SQL_TRACE TRUE. This command captures all processed SQL statements in a trace file, which can be used for debugging. The location of the trace file is operating-system dependent and can be modified using the USER_DUMP_DEST initialization parameter.


See Also:

For more information about SQL trace and the USER_DUMP_DEST initialization parameter, see Oracle Database Administrator's Guide

-pk

Specify the primary key value of the row to be updated or exported.

When the primary key is compound, you must enclose the values within double quotes and separate the keys with a comma.

-export

Exports the contents of a CLOB or BLOB column in a database table into the operating system file specified by -file. ctxload exports the CLOB or BLOB column in the row specified by -pk.

When you use the -export, you must specify a primary key with -pk.

-update

Updates the contents of a CLOB or BLOB column in a database table with the contents of the operating system file specified by -file. ctxload updates the CLOB or BLOB column in for the row specified by -pk.

When you use -update, you must specify a primary key with -pk.

ctxload Examples

This section provides examples for some of the operations that ctxload can perform.


See Also:

For more document loading examples, see Appendix C, "Text Loading Examples for Oracle Text".

Thesaurus Import Example

The following example imports a thesaurus named tech_doc from an import file named tech_thesaurus.txt:

ctxload -user jsmith/123abc -thes -name tech_doc -file tech_thesaurus.txt 

Thesaurus Export Example

The following example dumps the contents of a thesaurus named tech_doc into a file named tech_thesaurus.out:

ctxload -user jsmith/123abc -thesdump -name tech_doc -file tech_thesaurus.out 

Knowledge Base Extension Compiler (ctxkbtc)

The knowledge base is the information source Oracle Text uses to perform theme analysis, such as theme indexing, processing ABOUT queries, and document theme extraction with the CTX_DOC package. A knowledge base is supplied for English and French.

With the ctxkbtc compiler, you can do the following:

Knowledge Base Character Set

Knowledge bases can be in any single-byte character set. Supplied knowledge bases are in WE8ISO8859P1. You can store an extended knowledge base in another character set such as US7ASCII.

ctxkbtc Syntax

ctxkbtc -user uname/passwd
[-name thesname1 [thesname2 ... thesname16]]
[-revert]
[-stoplist stoplistname]
[-verbose]
[-log filename]
-user

Specify the user name and password for the administrator creating an extended knowledge base. This user must have write permission to the ORACLE_HOME directory.

-name thesname1 [thesname2 ... thesname16]

Specify the name(s) of the thesauri (up to 16) to be compiled with the knowledge base to create the extended knowledge base. The thesauri you specify must already be loaded with ctxload with the "-thescase Y" option

-revert

Reverts the extended knowledge base to the default knowledge base provided by Oracle Text.

-stoplist stoplistname

Specify the name of the stoplist. Stopwords in the stoplist are added to the knowledge base as useless words that are prevented from becoming themes or contributing to themes. You can still add stopthemes after running this command using CTX_DLL.ADD_STOPTHEME.

-verbose

Displays all warnings and messages, including non-Globalization Support messages, to the standard output.

-log

Specify the log file for storing all messages. When you specify a log file, no messages are reported to standard out.

ctxkbtc Usage Notes

  • Before running ctxkbtc, you must set the NLS_LANG environment variable to match the database character set.

  • The user issuing ctxkbtc must have write permission to the ORACLE_HOME, since the program writes files to this directory.

  • Before being compiled, each thesaurus must be loaded into Oracle Text case sensitive with the "-thescase Y" option in ctxload.

  • Running ctxkbtc twice removes the previous extension.

ctxkbtc Limitations

The ctxkbtc program has the following limitations:

  • When upgrading or downgrading your database to a different release, Oracle recommends that you recompile your extended knowledge base in the new environment for theme indexing and related features to work correctly.

  • Before extending the knowledge base, you must terminate all server processes which invoked any knowledge base related Text functions during their lifetime.

  • There can be only one user extension for each language for each installation. Since a user extension affects all users at the installation, only the CTXSYS user can extend the knowledge base.

ctxkbtc Constraints on Thesaurus Terms

Terms are case sensitive. If a thesaurus has a term in uppercase, for example, the same term present in lowercase form in a document will not be recognized.

The maximum length of a term is 80 characters.

Disambiguated homographs are not supported.

ctxkbtc Constraints on Thesaurus Relations

The following constraints apply to thesaurus relations:

  • BTG and BTP are the same as BT. NTG and NTP are the same as NT.

  • Only preferred terms can have a BT, NTs or RTs.

  • If a term has no USE relation, it will be treated as its own preferred term.

  • If a set of terms are related by SYN relations, only one of them may be a preferred term.

  • An existing category cannot be made a top term.

  • There can be no cycles in BT and NT relations.

  • A term can have at most one preferred term and at most one BT. A term may have any number of NTs.

  • An RT of a term cannot be an ancestor or descendent of the term. A preferred term may have any number of RTs up to a maximum of 32.

  • The maximum height of a tree is 16 including the top term level.

  • When multiple thesauri are being compiled, a top term in one thesaurus should not have a broader term in another thesaurus.


    Note:

    The thesaurus compiler will tolerate certain violations of the preceding rules. For example, if a term has multiple BTs, it ignores all but the last one it encounters.

    Similarly, BTs between existing knowledge base categories will only result in a warning message.

    Such violations are not recommended since they might produce undesired results.


Extending the Knowledge Base

You can extend the supplied knowledge base by compiling one or more thesauri with the Oracle Text knowledge base. The extended information can be application-specific terms and relationships. During theme analysis, the extended portion of the knowledge base overrides any terms and relationships in the knowledge base where there is overlap.

When extending the knowledge base, Oracle recommends that new terms be linked to one of the categories in the knowledge base for best results in theme proving when appropriate.


See Also:

For complete description of the supplied knowledge base, see http://www.oracle.com/technology/products/text/

If new terms are kept completely disjoint from existing categories, fewer themes from new terms will be proven. The result of this is poorer precision and recall with ABOUT queries as well poor quality of gists and theme highlighting.

You link new terms to existing terms by making an existing term the broader term for the new terms.

Example for Extending the Knowledge Base

You purchase a medical thesaurus medthes containing a hierarchy of medical terms. The four top terms in the thesaurus are the following:

  • Anesthesia and Analgesia

  • Anti-Allergic and Respiratory System Agents

  • Anti-Inflammatory Agents, Antirheumatic Agents, and Inflammation Mediators

  • Antineoplastic and Immunosuppressive Agents

To link these terms to the existing knowledge base, add the following entries to the medical thesaurus to map the new terms to the existing health and medicine branch:

health and medicine
 NT Anesthesia and Analgesia
 NT Anti-Allergic and Respiratory System Agents
 NT Anti-Inflamammatory Agents, Antirheumatic Agents, and Inflamation Mediators
 NT Antineoplastic and Immunosuppressive Agents

Set your Globalization Support language environment variable to match the database character set. For example, if your database character set is WE8ISO8859P1 and you are using American English, set your NLS_LANG as follows:

setenv NLS_LANG AMERICAN_AMERICA.WE8ISO8859P1

Assuming the medical thesaurus is in a file called med.thes, you load the thesaurus as medthes with ctxload as follows:

ctxload -thes -thescase y -name medthes -file med.thes -user ctxsys/ctxsys

To link the loaded thesaurus medthes to the knowledge base, use ctxkbtc as follows:

ctxkbtc -user ctxsys/ctxsys -name medthes 

Adding a Language-Specific Knowledge Base

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

Theme functionality includes theme indexing, ABOUT queries, theme highlighting, and the generation of themes, gists, and theme summaries with the CTX_DOC PL/SQL package.

You extend theme functionality by adding a user-defined knowledge base. For example, you can create a Spanish knowledge base from a Spanish thesaurus.

To load your language-specific knowledge base, follow these steps:

  1. Load your custom thesaurus using ctxload.

  2. Set NLS_LANG so that the language portion is the target language. The charset portion must be a single-byte character set.

  3. Compile the loaded thesaurus using ctxkbtc:

ctxkbtc -user ctxsys/ctxsys -name my_lang_thes

This command compiles your language-specific knowledge base from the loaded thesaurus. To use this knowledge base for theme analysis during indexing and ABOUT queries, specify the NLS_LANG language as the THEME_LANGUAGE attribute value for the BASIC_LEXER preference.

Limitations for Adding a Knowledge Base

The following limitations hold for adding knowledge bases:

  • Oracle Text supplies knowledge bases in English and French only. You must provide your own thesaurus for any other language.

  • You can only add knowledge bases for languages with single-byte character sets. You cannot create a knowledge base for languages which can be expressed only in multibyte character sets. If the database is a multibyte universal character set, such as UTF-8, the NLS_LANG parameter must still be set to a compatible single-byte character set when compiling the thesaurus.

  • Adding a knowledge base works best for whitespace delimited languages.

  • You can have at most one knowledge base for each Globalization Support language.

  • Obtaining hierarchical query feedback information such as broader terms, narrower terms and related terms does not work in languages other than English and French. In other languages, the knowledge bases are derived entirely from your thesauri. In such cases, Oracle recommends that you obtain hierarchical information directly from your thesauri.

Order of Precedence for Multiple Thesauri

When multiple thesauri are to be compiled, precedence is determined by the order in which thesauri are listed in the arguments to the compiler (most preferred first). A user thesaurus always has precedence over the built-in knowledge base.

Size Limits for Extended Knowledge Base

Table 14-1 lists the size limits associated with creating and compiling an extended knowledge base:

Table 14-1 Size Limit for the Extended Knowledge Base

Description of Parameter Limit
Number of RTs (from + to) for each term 32
Number of terms for each single hierarchy (for example, all narrower terms for a given top term) 64000
Number of new terms in an extended knowledge base 1 million
Number of separate thesauri that can be compiled into a user extension to the KB 16

Lexical Compiler (ctxlc)

The Lexical Compiler (ctxlc) is a command-line utility that enables you to create your own Chinese and Japanese lexicons (dictionaries). Such a lexicon may either be generated from a user-supplied word list or from the merging of a word list with the system lexicon for that language.

ctxlc creates the new lexicon in your current directory. The new lexicon consists of three files, drold.dat, drolk.dat, and droli.dat. To change your system lexicon for Japanese or Chinese, overwrite the system lexicon with these files.

The Lexical Compiler can also generate wordlists from the system lexicons for Japanese and Chinese, enabling you to see their contents. These word lists go to the standard output and thus can be redirected into a file of your choice.

After overwriting the system lexicon, you need to re-create your indexes before querying them.

Syntax of ctxlc

ctxlc has the following syntax:

ctxlc -ja | -zh [ -n ] -ics character_set -i input_file

ctxlc -ja | -zh -ocs character_set [ > output_file ]

Mandatory Arguments

-ja | -zh

Specify the language of the lexicon to modify or create. -ja indicates the Japanese lexicon; -zh indicates the Chinese lexicon.

-ics character_set

Specify the character set of the input file denoted by -i input_file. input_file is the list of words, one word to a line, to use in creating the new lexicon.

-i input_file

Specify the file containing words to use in creating a new lexicon.

-ocs character_set

Specify the character set of the text file to be output.

Optional Arguments

-n

Specify -n to create a new lexicon that consists only of user-supplied words taken from input_file. If -n is not specified, then the new lexicon consists of a merge of the system lexicon with input_file. Also, when -n is not selected, a text file called drolt.dat, is created in the current directory to enable you to inspect the contents of the merged lexicon without having to issue another ctxlc command.

Performance Considerations

You can add up to 1,000,000 new words to a lexicon. However, creating a very large lexicon can cause a performance hit in indexing and querying. Performance is best when the lexicon character set is UTF-8. There is no performance impact on the Chinese or Japanese V-gram lexers, as they do not use lexicons.

ctxlc Usage Notes

Oracle recommends the following practices with regard to ctxlc:

  • Save your plain text dictionary file in your environment for emergency use.

  • When upgrading or downgrading your database to a different release, recompile your plain text dictionary file in the new environment so that the user lexicon will work correctly.

Example

In this example, you create a new Japanese lexicon from the file jadict.txt, a word list that uses the JA16EUC character set. Because you are not specifying -n, the new lexicon is the result of merging jadict.txt with the system Japanese lexicon. You then replace the existing Japanese lexicon with the new, merged one.

% ctxlc -ja -ics JA16EUC -i jadict.txt

This creates new files in the current directory:

% ls
drold.dat
drolk.dat
droli.dat
drolt.dat

The system lexicon files for Japanese and Chinese are named droldxx.dat drolkxx.dat, and drolixx.dat, where xx is either JA (for Japanese) or ZH (for Chinese). Rename the three new files and copy them to the directory containing the system Japanese lexicon.

% mv drold.dat droldJA.dat
% mv drolk.dat drolkJA.dat
% mv droli.dat droliJA.dat
% cp *dat $ORACLE_HOME/ctx/data/jalx

This replaces the system Japanese lexicon with one that is a merge of the old system lexicon and your wordlist from jadict.txt.

You can also use ctxlc to get a dump of a system lexicon. This example dumps the Chinese lexicon to a file called new_chinese_dict.txt in the current directory:

% ctxlc -zh -ocs UTF8 > new_chinese_dict.txt

This creates a file, new_japanese.dict.txt, using the UTF8 character set, in the current directory.