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Viewing Highlighted Text


This chapter describes how to view highlighted text using the PL/SQL procedures provided by ConText.

The topics covered in this chapter are:

Overview of Viewing

CTX_QUERY.HIGHLIGHT is a PL/SQL procedure provided by ConText to create various forms of the documents that can be used in an application to produce viewable output.

Other stored procedures in the CTX_QUERY package provide for managing the result tables used to store the viewing output.

CTX_QUERY.HIGHLIGHT Procedure

The PL/SQL procedure CTX_QUERY.HIGHLIGHTgenerates filtered text, marked-up highlight text, and highlight information. You typically call CTX_QUERY.HIGHLIGHT after executing a text query.

Use CTX_QUERY.HIGHLIGHT to generate the following output for a document:


Note:

If the document is an HTML document filtered through the internal HTML filter, the marked-up ASCII text version generated by HIGHLIGHT and stored in a MUTAB table retains the original HTML tags from the document.

 

See Also::

For more information about the structure of the highlight output tables, see "Highlight Table Structures" in Appendix A.

For more information about the Windows 32-bit viewer, see "Viewing in Windows" in this chapter.

 

Highlighting Mark-up

The markup that is used to indicate the start and end of a highlighted word or phrase can be specified when CTX_QUERY.HIGHLIGHT is called for a document.

If no markup is specified, HIGHLIGHT uses default markup. The default highlighting mark-up produced by HIGHLIGHT differs depending on the format of the source document.

If the source document is an ASCII document or a formatted document, the default highlighting markup is three angle brackets immediately to the left (<<<) and right (>>>) of each term.

If the source document is an HTML document filtered through an external filter, the default highlighting markup is the same as the highlighting markup for ASCII or formatted documents (<<< and >>>).

If the source document is an HTML document filtered through the internal HTML filter, the default highlighting markup is the HTML tags used to indicate the start and end of a font change:

See Also:

For more information about internal and external filters, see Oracle ConText Option Administrator's Guide.

 

Using CTX_QUERY.HIGHLIGHT

To provide document and highlight viewing in an application, you perform the following tasks:

  1. Allocate one or more highlight result tables to store the results.
  2. Issue a query to obtain a list of documents.
  3. Call the CTX_QUERY.HIGHLIGHT procedure for a document from the hitlist.
  4. Display (or otherwise use) the output generated by HIGHLIGHT.
  5. Release the result table(s).

Allocate Result Tables

The result tables required by the HIGHLIGHT procedure can be allocated manually using the CREATE TABLE command in SQL or using the CTX_QUERY.GETTAB procedure.

See Also:

For more information about the structure of the highlight output tables, see "Highlight Table Structures" in Appendix A.

 

Issue Query

Issue a one-step, two-step, or in-memory query to return a hitlist of documents. The hitlist provides the textkeys that are used to generate highlight and display output for specified documents in the hitlist.

Call CTX_QUERY.HIGHLIGHT

Call CTX_QUERY.HIGHLIGHT with a pointer to a document (generally the textkey obtained from the hitlist) and a query expression.


Note:

While the query expression is usually the same as the expression used to return documents in the text query, it is not required that the query expressions match. For example, you might allow a user to search for all articles by a particular author and then allow the user to view highlighted references to a specified subject in the returned documents.

 

CTX_QUERY. HIGHLIGHT returns various forms of the specified document that can be further processed or displayed by the application.

The highlight offset information and marked-up ASCII text are generated using the query expression specified in the HIGHLIGHT procedure. In addition, the offset information is based on the ASCII text version of the document.

Display HIGHLIGHT Output

Use the highlight table to manually mark up documents within the application or to display the documents returned by the HIGHLIGHT procedure.

Release Result Tables

After documents have been processed by the HIGHLIGHT procedure and displayed to the user, drop the highlight result tables.

If the tables were allocated using CTX_QUERY.GETTAB, you use CTX_QUERY.RELTAB to release the tables.

If the tables were created manually, drop the tables using the SQL command DROP TABLE.

CTX_QUERY.HIGHLIGHT Sample

In the following code sample, a table called MU_TEXT is created to receive marked-up documents. The CTX_QUERY.HIGHLIGHT procedure is then used to locate specific text in the documents and display the marked-up documents. The text to be searched for and marked up is the same.

To use the code sample, do the following:

  1. Copy the code in the sample and save it as a SQL script.
  2. Initiate a SQL*PLUS session and execute the script
.


Note:

As a prerequisite, this example assumes that the EMP demonstration table distributed with ConText has been installed, an Oracle database is running, and a ConText server has been started with the Query personality.

 

Code Sample

create table mu_text (id number, document long);
set termout off
set verify off
col ct	new_value	ct
col sess	new_value	sess
col score	format 990	head 'RANK'
col textkey	format a4	head 'KEY'
col document format a45 word_wrap
set long 60
/* Since this application uses a shared results table */
/* for the hitlist, the application must create a */
/* unique id for each user sharing the results table. */
/* In this example, the unique id is created from the */
/* "sessionid" parameter of the users environment. */
select userenv('sessionid') sess from dual;
/* Run an initial text query to return a hitlist */ begin ctx_query.contains ('EMP_HISTORY','&1','CTX_TEMP',1,&sess); end;
/* Count the hits */ select count(*) ct from EMP,CTX_TEMP where empno=textkey and conid=&sess;
/* Clear prior results from MU_TEXT */ delete MU_TEXT; commit;
declare tk varchar2(12) numtk number(10); mudoc varchar2(2000); cursor s is select textkey from CTX_TEMP,EMP where empno=textkey and conid=&sess;
begin open s; /*for each hit, produce a marked up row*/ for i in 1 ..&ct loop fetch s into tk; /*create numeric id for MU_TEXT from textkey*/ numtk := to_number(tk);
/* call ctx_query.highlight for each document using */
/* the same policy and query expression from the */
/* initial query. Create marked-up ASCII output for */
/* document, stored in mutab table named MU_TEXT. */ begin ctx_query.highlight( cspec => 'EMP_HISTORY', textkey => tk, query => '&1', id => numtk, mutab => 'MU_TEXT'); end;
end loop; end;
/*Join the hits with the marked-up docs*/
select score RANK, textkey KEY, document from CTX_TEMP, MU_TEXT where id=to_number(textkey) and conid=&sess order by score desc; set echo on

Example

In the following example, the sample code has been stored as a script named highlight.sql and the query term is the word used:

	@highlight 'used'

The output generated by HIGHLIGHT.SQL is:

	RANK	KEY	DOCUMENT
	-------------------
	10		7369	<<<Used>>> to build horse shoes
	10		7698	Blake <<<used>>> to be a manager at apple

The query term used was found in two documents (textkeys 7369 and 7698). CTX_QUERY.HIGHLIGHT highlighted the specified term using the default markup'<<<' and'>>>'.

Viewing in Windows

You can use the Oracle ConText Option Viewer Control (CTXV32.OCX) to allow users to view highlighted documents in a Windows 32-bit environment. The viewer enables the user to browse documents in the supported formats with query terms highlighted.

You embed the control in client-side applications. To operate the viewer, you need not write any PL/SQL code; given the database connection, the document textkey, and the query term, the viewer control displays the document with highlights.

The user can view a Word document, for example, as it would appear in Microsoft Word. The user can also scroll through the document using the Next and Previous buttons to jump to the next or previous occurrence of the search term(s).

Using the ConText Viewer Control

As OCX modules are not stand-alone executables, you need a development environment such as Visual C++ or Visual Basic to exploit the functionality of the ConText Viewer Control. Within such an environment, you can add the control to the tool palette, from where you can place instances of the control on a form or canvas.

For example, in Visual Basic 4.0, you add the control to the tool palette by selecting Custom Controls from the Tool menu. Use the browser to select the Oracle8 ConText Viewer Control, CTXV32.OCX, from the oracle_home\BIN directory.

Alternatively, you can create instances of the control dynamically, using the identification string"CTXV32.CTXViewer.1"

If the viewer control is embedded in an HTML page, the browser must support ActiveX components and the client machine must have the viewer installed on it with all required support files. The viewer uses SQL*Net to communicate with the database. Within HTML, you can invoke the methods using Visual Basic scripting, for example, and change properties with the OBJECT tag and parameter settings syntax.

.

See Also:

For more information about the methods and properties associated with the 32-bit viewer control, see the ConText Viewer Control help file, CTXV32.HLP. This file has Visual Basic and HTML examples.

 

Supported Formats

You can use the ConText Viewer Control to view documents in the following server-side supported formats:

Viewing Without the OCX

If you are not using the OCX to view documents in 32-bit Windows environment, you can use the ConText I/O utility (CTXIO32) to move documents (highlighted or not) from database tables to the client operating system and vice-versa. Documents downloaded to the client operating system can be viewed in their native applications.

See Also:

For more information about the 32-bit Windows I/O utility, see the Oracle ConText Option Workbench User's Guide.

 




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