4
Document Presentation

This chapter describes document presentation. The following topics are covered:

• Highlighting Query Terms
• Obtaining List of Themes, Gists, and Theme Summaries

Highlighting Query Terms

In Oracle 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, a plain text version of the document (filtered output), and highlight offset information for the document.

The three types of output are generated by three different procedures in the CTX_DOC (document services) PL/SQL package. In addition, you can obtain plain text and HTML versions for each type of output.

Text highlighting

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

Theme Highlighting

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

CTX_DOC Highlighting Procedures

There are three highlighting procedures in CTX_DOC:

• CTX_DOC.HIGHLIGHT
• CTX_DOC.MARKUP
• CTX_DOCFILTER

Highlight Procedure

Highlight offset information is useful for when you write your own custom routines for displaying documents.

To obtain highlight offset information, use the CTX_DOC.HIGHLIGHT procedure. This procedure takes a query and a document, and returns highlight offset information for either plaintext or HTML formats.

With offset information, you can display a highlighted version of document as desired. For example, you can display the document with different font types or colors rather than using the standard plain text markup obtained from CTX_DOC.MARKUP.

Markup Procedure

The CTX_DOC.MARKUP procedure takes a document reference and a query, and returns a marked-up version of the document. The output can be either marked-up plaintext or marked-up HTML.

You can customize the markup sequence for HTML navigation.

Filter Procedure

When documents are stored in their native formats such as Microsoft Word, you can use the filter procedure CTX_DOC.FILTER to obtain either a plain text or HTML version of the document.

Obtaining List of Themes, Gists, and Theme Summaries

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

Table 4-1

Output Type	Description
List of Themes	A list of the main concepts of a document. You can generate list of themes where each theme is a single word or phrase or where each theme is a hierarchical list of parent themes.
Gist	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 this output, you use procedures in the CTX_DOC supplied package. With this package, you can do the following:

• Identify documents by ROWID in addition to primary key
• Store results in-memory for improved performance

List 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.

In-Memory Themes

The following 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.

declare
 the_themes ctx_doc.theme_tab;

begin
 ctx_doc.themes('myindex','1',the_themes, numthemes=>10);
 for i in 1..the_themes.count loop
  dbms_output.put_line(the_themes(i).theme||':'||the_themes(i).weight);
  end loop;
end;

Result Table Themes

To create a theme table:

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

Single Themes

To obtain a list of themes where each element in the list is a single theme, issue:

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

Full Themes

To obtain a list of themes where each element in the list is a hierarchical list of parent themes, issue:

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

Gist and Theme Summary

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

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

In-Memory Gist

The following example generates a non-default 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.

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

begin
 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
  dbms_lob.freetemporary(gklob);
 end;

Result Table Gists

To create a gist table:

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

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

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

The following example generates a non-default size gist of ten paragraphs:

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

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

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

Theme Summary

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

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