Classification Application Quick Tour

2.5 Classification Application Quick Tour

The function of a classification application is to perform some action based on document content. These actions can include assigning a category ID to a document or sending the document to a user. The result is classification of a document.

This section contains the following sections:

2.5.1 About Classification of a Document

Documents are classified according to predefined rules. These rules select documents for a category. For instance, a query rule of 'presidential elections' selects documents for a category about politics.

Oracle Text provides several types of classification. One type is simple, or rule-based classification, discussed here, where you create document categories and the rules for categorizing documents. With supervised classification, Oracle Text derives the rules from a set of training documents that you provide. With clustering, Oracle Text does all the work for you, deriving both rules and categories.

To create a simple classification application for document content using Oracle Text, you create rules. Rules are essentially a table of queries that categorize document content. You index these rules in a CTXRULE index. To classify an incoming stream of text, use the MATCHES operator in the WHERE clause of a SELECT statement. See the following image for the general flow of a classification application.

Figure 2-2 Overview of a Document Classification Application

Description of "Figure 2-2 Overview of a Document Classification Application"

2.5.2 Creating a Classification Application

The following example shows how to classify documents by using myuser with the CTXAPP role. You define simple categories, create a CTXRULE index, and use MATCHES.

Connect as the appropriate user.
Connect as the myuser with CTXAPP role:
```
CONNECT myuser;
```

Create the rule table.

In this example, you create a table called queries. Each row defines a category with an ID and a rule that is a query string.

CREATE TABLE queries (
      query_id      NUMBER,
      query_string  VARCHAR2(80)
    );

    INSERT INTO queries VALUES (1, 'oracle');
    INSERT INTO queries VALUES (2, 'larry or ellison');
    INSERT INTO queries VALUES (3, 'oracle and text');
    INSERT INTO queries VALUES (4, 'market share');

Create your CTXRULE index.

CREATE INDEX queryx ON queries(query_string) INDEXTYPE IS CTXSYS.CTXRULE;

Classify with MATCHES.

Use the MATCHES operator in the WHERE clause of a SELECT statement to match documents to queries and then classify the documents.

    COLUMN query_string FORMAT a35;
    SELECT query_id,query_string FROM queries
     WHERE MATCHES(query_string, 
                   'Oracle announced that its market share in databases 
                    increased over the last year.')>0;

  QUERY_ID QUERY_STRING                                                         
---------- -----------------------------------                                  
         1 oracle                                                               
         4 market share

As shown, the document string matches categories 1 and 4. With this classification, you can perform an action, such as writing the document to a specific table or emailing a user.