|Oracle® Text Application Developer's Guide
11g Release 2 (11.2)
|PDF · Mobi · ePub|
In Oracle Text, alternate spelling refers specifically to the use of spelling variations in German, Swedish, and Dutch; these variations may be indexed if the
ALTERNATE_SPELLING has been specified.
An attribute is an optional parameter associated with a preference. For example, the
BASIC_LEXER preference includes the
base_letter attribute, which can have either the value of
YES (perform base-letter conversions) or
NO (do not perform such conversions). Attributes are set with the
CTX_DDL.SET_ATTRIBUTE procedure or with the
ALTER INDEX statement. See also: preference, base-letter conversion.
A user-defined section, representing an attribute of an XML document, such as
TITLE. Attribute sections are added to section groups with
CTX_DDL.ADD_ATTR_SECTION or with the
ALTER INDEX statement. See also: AUTO_SECTION_GROUP, section, XML_SECTION_GROUP.
A section group used to automatically crate a zone section for each start-and end-tag pair in an XML document; attribute sections are automatically created for XML tags that have attributes. See also: attribute section, section, section group, XML_SECTION_GROUP, zone section.
The conversion of a letter with alternate forms (such as accents, umlauts, or cedillas) to its basic form (for example, without an accent).
A section group used to define sections where the start and end tags are of the form <tag> and </tag>. It does not support non-basic tags, such as comment tags or those with attributes or unbalanced parentheses. See also: HTML_SECTION_GROUP, section, section group.
Case refers to the capitalization of a word or letter, where upper-case letters are capitals (M instead of m, for example). Not all languages have case. Mixed-case indexing is supported for some languages, notably those of Western Europe.
Also known as document classification. The conceptual separation of source documents into groups, or clusters, based on their content. For example, a group of documents might be separated into clusters concerning medicine, finance, and sports.
Oracle Text includes rule-based classification, in which a person writes the rules for classifying documents (in the form of queries), and Oracle Text performs the document classification according to the rules; supervised classification, in which Oracle Text creates classification rules based on a set of sample documents; and clustering (also known as unsupervised classification), in which the clusters and rules are both created by Oracle Text.
Also known as unsupervised classification. See: classification.
Also known as CDI type of index. An Oracle Text index that not only indexes and processes a specified text column, but also indexes and processes
BY structured columns that are specified during index creation. See also: domain index.
The basic type of Oracle Text index; an index on a text column. A
CONTEXT index is useful when your source text consists of many large, coherent documents. Applications making use of
CONTEXT indexes use the
CONTAINS query operator to retrieve text.
A role for application developers that enables a user to create Oracle Text indexes and index preferences, and to use PL/SQL packages. This role should be granted to Oracle Text users.
A combined index on a text column and one or more other columns. Typically used to index small documents or text fragments, such as item names, prices and descriptions typically found in catalogs. The
CTXCAT index typically has better mixed-query performance than the
Applications query this index with the
CATSEARCH operator. This index is transactional, which means that it automatically updates itself with DML to the base table.
CTXRULE index is used to build a document classification application. The
CTXRULE index is an index created on a table of queries, where the queries serve as rules to define the classification criteria. This index is queried with the
CTXSYS user is created at install time. The
CTXSYS user can view all indexes; sync all indexes; run
ctxkbtc, the knowledge base extension compiler; query all system-defined views; and perform all the tasks of a user with the
In Oracle Text, datastore refers to the method of storing text. The method is determined by specifying a storage preference of a particular type. For example, the
DIRECT_DATASTORE type stores data directly into the text column, while the
URL_DATASTORE specifies that data is stored externally in a location specified by a URL.
An Oracle Database domain index that indexes and processes a specified text column. See also: composite domain index.
One or more non-alphanumeric characters that, when encountered as the last character in a token, explicitly identify the end of the token. The characters, as well as any startjoin characters that immediately follow it, are included in the Text index entry for the token. For example, if ++ is specified as an endjoin, then C++ will be recognized and indexed as a single token. See also: printjoin, skipjoin, startjoin.
A field section is similar to a zone section, with the main difference that the content between the start and end tags of a field section can be indexed separately from the rest of the document. This enables field section content to be "hidden" from a normal query. (The
WITHIN operators may be used to find the term in such a section.) Field sections are useful when there is a single occurrence of a section in a document, such as a filed in a news header. Field sections are added to section groups with the
CTX_DDL.ADD_FIELD_SECTION procedure or with the
ALTER INDEX statement. See also: INPATH operator, section, WITHIN operator, zone section.
One of the steps in the Oracle Text index-creation process. Depending on the filtering preferences associated with the creation of the index, one of three things happens during filtering: Formatted documents are filtered into marked-up text; text is converted from a non-database character set to a database character set; or no filtering takes place (HTML, XML, and plain-text documents are not filtered).
A fuzzy-matching query is one in which the query is expanded to include words that are spelled similarly to the specified term. This type of expansion is helpful for finding more accurate results when there are frequent misspellings in a document set. Fuzzy matching is invoked with the
FUZZY query operator.
CONTAINS query operator used to find XML documents that contain a section path exactly as specified in the query. See also: PATH_SECTION_GROUP.
Generically, in Oracle Text, highlighting refers to generating a version of a document, or document fragments, with query terms displayed or called out in a special way.
Specifically, there are three forms of highlighting. First,
CTX_DOC.MARKUP returns a document with the query term surrounded by plaintext or HTML tags. Second,
CTX_DOC.HIGHLIGHT returns offsets for the query terms, allowing the user to mark up the document as desired. Third,
CTX_DOC.SNIPPET produces a concordance, with the query term displayed in fragments of surrounding text. markup.
CONTAINS query operator used to search within tags, or paths, of an XML document. It enables more generic path denomination than the
WITHIN operator. See also: WITHIN operator.
In Oracle Text, a presentation of a query term with the text that surrounds it in the source document. This presentation may consist of a single instance of the query term, several instances, or every instance in the source document. The
CTX_DOC.SNIPPET procedure produces such a presentation. Also known as Key Word in Context (KWIC).
Oracle Text includes a knowledge base, which is a hierarchical tree of concepts used for theme indexing,
ABOUT queries, and deriving themes for document services. The knowledge base may be optionally installed. You can create your own knowledge base or extend the standard Oracle Text knowledge base.
The Oracle Text lexer breaks source text into tokens—usually words—in accordance with a specified language. To extract tokens, the lexer uses parameters as defined by a lexer preference. These parameters include the definitions for the characters that separate tokens, such as whitespace, and whether to convert text to all uppercase or not. When theme indexing is enabled, the lexer analyses text to create theme tokens.
When an application needs to index a table containing documents in more than one language, it can utilize the
MULTI_LEXER (the multilingual lexer) and create sub-lexers to handle each language. Each sub-lexer is added to the main multi-lexer with the
A form of highlighting. The
CTX_DOC.POLICY_MARKUP procedures take a query term and a document, and return the document with the query terms marked up; that is, surrounded either by plaintext characters or HTML tags. You can use predefined markup tags or specify your own. In comparison,
CTX_DOC.POLICY_HIGHLIGHT return offsets for query terms, so you can add your own highlighting tags. See also: highlighting.
Metadata is information about a document that is not part of a document's regular content. For example, if an HTML document contains
<author>Mark Twain</author>, author is considered the metadata type and Mark Twain is considered the value for
Sections containing metadata, known as
MDATA sections, can be added to a document with the
CTX_DDL.ADD_MDATA_SECTION procedure. Taking advantage of metadata can speed up mixed queries. Such queries can be made with the
MDATA operator. See also: mixed query, section.
A query that searches for two different types of information; for example, text content and document type. For example, a search for Romeo and Juliet in
<title> metadata is a mixed query.
Name searching (also called name matching) provides a solution to match proper names that might differ in spelling due to orthographic variation. It also enables you to search for somewhat inaccurate data, such as might occur when a record's first name and surname are not properly segmented.
The form of a word after it has been transformed for indexing, according to transformational rules in effect. Depending on the rules in effect, the normalized form of a word may be the same as the form found in the source document. The normalized form of a word may also include both the original and transformed versions. For example, if New German Spelling has been specified, the word Potential is normalized to both Potenzial and Potential.
A section group type used for indexing XML documents. It is similar to the
AUTO_SECTION_GROUP type, except that it enables the use of the
INPATH operators. See also: AUTO_SECTION_GROUP, HASPATH operator, INPATH operator, section, section group.
A preference is an optional parameter that affects the way Oracle Text creates an index. For example, a lexer preference specifies the lexer to use when processing documents, such as the
JAPANESE_VGRAM_LEXER. There are preferences for storage, filtering, lexers, classifiers, wordlist, section types, and more. A preference may or may not have attributes associated with it. Preferences are set with the
CTX_DDL.CREATE_PREFERENCE procedure. See also: attribute.
One or more non-alphanumeric character that, when they appear anywhere in a word (beginning, middle, or end), are processed as alphanumeric and included with the token in an Oracle Text index. This includes printjoins that occur consecutively.
For example, if the hyphen (-) and underscore (_) characters are defined as printjoins, terms such as pseudo-intellectual and _file_ are stored in the Oracle Text index as pseudo-intellectual and _file_.
Printjoins differ from endjoins and startjoins in that position does not matter. For example, $35 will be indexed as one token if $ is defined as a startjoin or a printjoin, but as two tokens if it is an endjoin. See also: endjoin, printjoin, startjoin.
A page of search results in applications can consist of many disparate elements — metadata of the first few documents, total hit counts, per-word hit counts, and so on. Generating these results in earlier versions of Oracle Text required several queries and calls. Each extra call takes time to reparse the query and look up index metadata. Additionally, some search operations, such as iterative query refinement or breakdown top ten, are difficult for SQL.
The result set interface enables you to produce the various kinds of data needed for a page of search results all at once, thus improving performance by sharing overhead. The result set interface can also return data views that are difficult to express in SQL, such as top N by category queries.
Structured/Sort Data section. Unlike the
MDATA section type, which only supports equality searches,
SDATA sections are designed to also support range searches. By default, all
BY columns are mapped as
SDATA sections. An
SDATA section contains user-defined index metadata. Use of this type of section can speed up mixed
CONTAINS queries. See also: mixed query, section.
A section is a subdivision of a document; for example, everything within an
<a>...</a> section of an HTML page.
Dividing a document into sections and then searching within sections enables you to narrow text queries down to blocks of text within documents. Section searching is useful when your documents have internal structure, such as HTML and XML documents. You can also search for text at the sentence and paragraph level.
Section searching is performed with the
WITHIN operator. Sections searching is enabled by the used of the section group when indexing.
The various section types include attribute, field, HTML, MDATA, special, stop, XML, and zone sections.
A section group identifies a type of document set and implicitly indicate the tag structure for indexing. For instance, to index HTML tagged documents, you use the
HTML_SECTION_GROUP. section group type. Likewise, to index XML tagged documents, you can use the
XML_SECTION_GROUP section group type. Section groups are declared with the
CTX_DDL.CREATE_SECTION_GROUP procedure or with the
ALTER INDEX statement. See also: section.
A non-alphanumeric character that, when it appears within a word, identifies the word as a single token; however, the character is not stored with the token in the Text index. For example, if the hyphen character '-' is defined as a skipjoin, the word pseudo-intellectual is stored in the Text index as pseudointellectual. See also: endjoin, printjoin, startjoin.
One or more non-alphanumeric characters that, when encountered as the first character in a token explicitly identify the start of the token. The characters, as well as any other startjoins characters that immediately follow it, are included in the Text index entry for the token. For example, if '$' is defined as a startjoin, then $35 is indexed as a single token. In addition, the first startjoins character in a string of startjoins characters implicitly ends the previous token. See also: endjoin, printjoin, skipjoin.
The expansion of a query term to include all terms having the same root word. For example, stemming the verb talk yields talking, talks, and talked, as well as talk (but not talkie). Stemming is distinct from wildcard expansion, in which results are related only through spelling, not through morphology. See also: wildcard expansion.
A document section that is not bounded by tags. Instead, sections are formed by plaintext document structures such as sentences and paragraphs. Special sections are added to a section group with the
CTX_DDL.ADD_SPECIAL_SECTION procedure. See also: section, section group.
A section that, when added to an
AUTO_SECTION_GROUP, causes the information for document sections of that type to be ignored during indexing; the section content may still be searched, however. Stop sections are added to section groups with the
CTX_DDL.ADD_STOP_SECTION procedure. See also: AUTO_SECTION_GROUP, section, section group.
A class of tokens, such as
NUMBERs, that are to be skipped over during indexing. Stopclasses are specified by adding them to stoplists with
CTX_DDL.ADD_STOPCLASS. See also: stoplist.
A list of words, known as stopwords, themes (stopthemes), and data classes (stopclasses) that are not to be indexed. By default, the system indexes text using the system-supplied stoplist that corresponds to a given database language.
Oracle Text provides default stoplists for most common languages including English, French, German, Spanish, Chinese, Dutch, and Danish. These default stoplists contain only stopwords. Stoplists are created with
CTX_DDL.CREATE_STOPLIST or with the
ALTER INDEX statement. See also: stopclass, stoptheme, stopword.
A theme to be skipped over during indexing. Stopthemes are specified by adding them to stoplists with
CTX_DDL.ADD_STOPTHEMES. See also: stoplist.
A word to be skipped over during indexing. Stopwords are specified by adding them to stoplists with
CTX_DDL.ADD_STOPWORD. They can also be dynamically added to an index using the
ALTER INDEX statement. See also: stoplist.
A topic associated with a given document. A document may have many themes. A theme does not have to appear in a document; for example, a document containing the words San Francisco may have California as one of its themes.
Theme components are added to indexes with the
INDEX_THEMES attribute of the
BASIC_LEXER preference; they may be extracted from a document with
CTX_DOC.THEMES and queried with the
The expansion of a query term to return words that fit a given pattern. For example, expansion of the query term %rot% would return both trot and rotten. Wildcard expansion is distinct from stemming. See also: stemming.
Characters that are treated as blank spaces between tokens. The predefined default values for whitespace are 'space' and 'tab'. The
BASIC_LEXER uses whitespace characters (in conjunction with punctuations and newline characters) to identify character strings that serve as sentence delimiters for sentence and paragraph searching.
CONTAINS query operator used to search for query terms within a given XML document section. It is similar to the
INPATH operator, but less generic. See also: INPATH operator.
An Oracle Text preference that enables features such as fuzzy, stemming, and prefix indexing for better wildcard searching, as well as substring and prefix indexing. The wordlist preference improves performance for wildcard queries with
CATSEARCH. Create wordlists with the
CTX_DDL.ADD_WORDLIST procedure or with the
ALTER INDEX statement. See also: preference.
A section that defined by XML tags, enabling XML section searching. Indexing with XML sections permits automatic sectioning as well as declaring document-type-sensitive sections. XML section searching includes attribute searching as well as path section searching with the
WITHIN operators. See also: section.
The basic type of document section; a body of text delimited by start and end tags in a document. Zone sections are well suited for defining sections in HTML and XML documents. Zone sections are added to section groups with the
CTX_DDL.ADD_ZONE_SECTION procedure or with the
ALTER INDEX statement. See also: field section, section, section group.