8 Presenting Documents in Oracle Text

Oracle Text provides various methods for presenting documents in results for query applications.

This chapter contains the following topics:

8.1 Highlighting Query Terms

In text query applications, you can present selected documents with query terms highlighted for text queries or with themes highlighted for ABOUT queries.

You can generate three types of output associated with highlighting:

  • A marked-up version of the document

  • Query offset information for the document

  • A concordance of the document, in which occurrences of the query term are returned with their surrounding text

This section contains the following topics:

8.1.1 Text highlighting

For text highlighting, you supply the query, and Oracle Text highlights words in the document that satisfy the query. You can obtain plain-text or HTML highlighting.

8.1.2 Theme Highlighting

For ABOUT queries, the CTX_DOC procedures highlight and mark up words or phrases that best represent the ABOUT query.

8.1.3 CTX_DOC Highlighting Procedures

These are the highlighting procedures in CTX_DOC:




The POLICY and non-POLICY versions of the procedures are equivalent, except that the POLICY versions do not require an index.


SNIPPET can also be generated using the Result Set Interface.

See Also:

Oracle Text Reference for information on CTX_QUERY.RESULT_SET

This section contains these topics: Markup Procedure

The CTX_DOC.MARKUP and CTX_DOC.POLICY_MARKUP procedures take a document reference and a query, and return a marked-up version of the document. The output can be either marked-up plain text or marked-up HTML. For example, specify that a marked-up document be returned with the query term surrounded by angle brackets (<<<tansu>>>) or HTML (<b>tansu</b>).

CTX_DOC.MARKUP and CTX_DOC.POLICY_MARKUP are equivalent, except that CTX_DOC.POLICY_MARKUP does not require an index.

You can customize the markup sequence for HTML navigation.


The following example is taken from the web application described in CONTEXT Query Application. The showDoc procedure takes an HTML document and a query, creates the highlight markup—in this case, the query term is displayed in red—and outputs the result to an in-memory buffer. It then uses htp.print to display it in the browser.

procedure showDoc (p_id in varchar2, p_query in varchar2) is

 v_clob_selected   CLOB;
 v_read_amount     integer;
 v_read_offset     integer;
 v_buffer          varchar2(32767);
 v_query           varchar(2000);
 v_cursor          integer;

   htp.p('<html><title>HTML version with highlighted terms</title>');
   htp.p('<body bgcolor="#ffffff">');
   htp.p('<b>HTML version with highlighted terms</b>');

     ctx_doc.markup (index_name => 'idx_search_table',
                     textkey    => p_id,
                     text_query => p_query,
                     restab     => v_clob_selected,
                     starttag   => '<i><font color=red>',
                     endtag     => '</font></i>');

     v_read_amount := 32767;
     v_read_offset := 1;
        v_read_offset := v_read_offset + v_read_amount;
        v_read_amount := 32767;
      end loop;
      when no_data_found then

      when others then
        null; --showHTMLdoc(p_id);
end showDoc;
show errors
set define on

See Also:

Oracle Text Reference for more information about CTX_DOC.MARKUP and CTX_DOC.POLICY_SNIPPET Highlight Procedure

CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT take a query and a document and return offset information for the query in plain text or HTML format. You can use this offset information to write your own custom routines for displaying documents.

CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT are equivalent, except that CTX_DOC.POLICY_HIGHLIGHT does not require an index.

With offset information, you can display a highlighted version of a document (such as different font types or colors) instead of the standard plain-text markup obtained from CTX_DOC.MARKUP.

See Also:

Oracle Text Reference for more information about using CTX_DOC.HIGHLIGHT and CTX_DOC.POLICY_HIGHLIGHT Concordance

CTX_DOC.SNIPPET and CTX_DOC.POLICY_SNIPPET produce a concordance of the document, in which occurrences of the query term are returned with their surrounding text. This result is sometimes known as Key Word in Context (KWIC) because, instead of returning the entire document (with or without the query term highlighted), it returns the query term in text fragments, allowing a user to see it in context. You can control how the query term is highlighted in the returned fragments.

CTX_DOC.SNIPPET and CTX_DOC.POLICY_SNIPPET are equivalent, except that CTX_DOC.POLICY_SNIPPET does not require an index. CTX_DOC.POLICY_SNIPPET and CTX_DOC.SNIPPET include two new attributes: radius specifies the approximate desired length of each segment, whereas, max_length puts an upper bound on the length of the sum of all segments.

See Also:

Oracle Text Reference for more information about CTX_DOC.SNIPPET and CTX_DOC.POLICY_SNIPPET

8.2 Obtaining Part-of-Speech Information for a Document

The CTX_DOC package contains procedures to create policies for obtaining part-of-speech information for a given document. This approach is described under POLICY_NOUN_PHRASES in Oracle Text Reference and POLICY_PART_OF_SPEECH in Oracle Text Reference.

8.3 Obtaining Lists of Themes, Gists, and Theme Summaries

The following table describes lists of themes, gists, and theme summaries.

Table 8-1 Lists of Themes, Gists, and Theme Summaries

Output Type Description

List of Themes

A list of the main concepts of a document.

Each theme is a single word, a single phrase, or a hierarchical list of parent themes.


Text in a document that best represents what the document is about as a whole.

Theme Summary

Text in a document that best represents a given theme in the document.

To obtain lists of themes, gists, and theme summaries, use procedures in the CTX_DOC package to:

  • Identify documents by ROWID in addition to primary key

  • Store results in-memory for improved performance

8.3.1 Lists of Themes

A list of themes is a list of the main concepts in a document. Use the CTX_DOC.THEMES procedure to generate lists of themes.

See Also:

Oracle Text Reference to learn more about the command syntax for CTX_DOC.THEMES

The following in-memory theme example generates the top 10 themes for document 1 and stores them in an in-memory table called the_themes. The example then loops through the table to display the document themes.

 the_themes ctx_doc.theme_tab;

 ctx_doc.themes('myindex','1',the_themes, numthemes=>10);
 for i in 1..the_themes.count loop
  end loop;

The following example create a result table theme:

create table ctx_themes (query_id number, 
                         theme varchar2(2000), 
                         weight number);

In this example, you obtain a list of themes where each element in the list is a single theme:

ctx_doc.themes('newsindex','34','CTX_THEMES',1,full_themes => FALSE);

In this example, you obtain a list of themes where each element in the list is a hierarchical list of parent themes:

ctx_doc.themes('newsindex','34','CTX_THEMES',1,full_themes => TRUE);

8.3.2 Gist and Theme Summary

A gist is the text in a document that best represents what the document is about as a whole. A theme summary is the text in a document that best represents a single theme in the document.

Use the CTX_DOC.GIST procedure to generate gists and theme summaries. You can specify the size of the gist or theme summary when you call the procedure.

See Also:

Oracle Text Reference to learn about the command syntax for CTX_DOC.GIST

In-Memory Gist Example

The following example generates a nondefault size generic gist of at most 10 paragraphs. The result is stored in memory in a CLOB locator. The code then de-allocates the returned CLOB locator after using it.

  gklob clob;
  amt number := 40;
  line varchar2(80);

 ctx_doc.gist('newsindex','34','gklob',1,glevel => 'P',pov => 'GENERIC',       numParagraphs => 10);
  -- gklob is NULL when passed-in, so ctx-doc.gist will allocate a temporary
  -- CLOB for us and place the results there.
  dbms_lob.read(gklob, amt, 1, line);
  dbms_output.put_line('FIRST 40 CHARS ARE:'||line);
  -- have to de-allocate the temp lob

Result Table Gists Example

To create a gist table, enter the following:

create table ctx_gist (query_id  number,
                       pov       varchar2(80), 
                       gist      CLOB);

The following example returns a default-sized paragraph gist for document 34:

ctx_doc.gist('newsindex','34','CTX_GIST',1,'PARAGRAPH', pov =>'GENERIC');

The following example generates a nondefault size gist of 10 paragraphs:

ctx_doc.gist('newsindex','34','CTX_GIST',1,'PARAGRAPH', pov =>'GENERIC',        numParagraphs => 10);

The following example generates a gist whose number of paragraphs is 10 percent of the total paragraphs in the document:

ctx_doc.gist('newsindex','34','CTX_GIST',1, 'PARAGRAPH', pov =>'GENERIC', maxPercent => 10);

Theme Summary Example

The following example returns a theme summary on the theme of insects for document with textkey 34. The default gist size is returned.

ctx_doc.gist('newsindex','34','CTX_GIST',1, 'PARAGRAPH', pov => 'insects');

8.4 Presenting and Highlighting Documents

Typically, a query application enables the user to view the documents returned by a query. The user selects a document from the hitlist, and then the application presents the document in some form.

With Oracle Text, you can display a document in different ways, such as highlighting either the words of a word query or the themes of an ABOUT query in English.

You can also obtain gist (document summary) and theme information from documents with the CTX_DOC PL/SQL package.

Table 8-2 describes the different output you can obtain and which procedure to use to obtain each type.

Table 8-2 CTX_DOC Output

Output Procedure

Plain-text version, no highlights


HTML version of document, no highlights


Highlighted document, plain-text version


Highlighted document, HTML version


Highlighted offset information for plain-text version


Highlighted offset information for HTML version


Theme summaries and gist of document


List of themes in document