How does oracle text differentiate between various document formats?

Question

how does oracle text differentiate between text documents of various formats. does it read binary headers or a file extension is necessary?
please comment..

Answer 1

Oracle uses the inso_filter for document filtering as desribed in the documentation:
http://download-west.oracle.com/docs/cd/B10501_01/text.920/a96518/afilsupt.htm#625110
I did a little test (included below) where I copied a .pdf file to a file with a .test extension and it was still able to index it and search it, so apparently it does not need the file extensions and must read the header.
scott@10gXE> BEGIN
  2   CTX_DDL.CREATE_PREFERENCE ('test_datastore', 'FILE_DATASTORE');
  3   CTX_DDL.SET_ATTRIBUTE ('test_datastore', 'PATH', 'c:\oracle');
  4  END;
  5  /
PL/SQL procedure successfully completed.
scott@10gXE> CREATE TABLE test_tab
  2    (id        NUMBER,
  3       docs        VARCHAR2 (2000),
  4       CONSTRAINT test_tab_id_pk PRIMARY KEY (id))
  5  /
Table created.
scott@10gXE> INSERT INTO test_tab VALUES (1, 'master~1.pdf')
  2  /
1 row created.
scott@10gXE> CREATE INDEX test_tab_idx ON test_tab (docs)
  2  INDEXTYPE IS CTXSYS.CONTEXT
  3  PARAMETERS
  4    ('DATASTORE test_datastore
  5        FILTER    CTXSYS.INSO_FILTER')
  6  /
Index created.
scott@10gXE> SELECT id FROM test_tab
  2  WHERE CONTAINS (docs, 'meat') > 0
  3  /
        ID                                                                     
         1                                                                     
scott@10gXE>
scott@10gXE> DROP INDEX test_tab_idx
  2  /
Index dropped.
scott@10gXE> HOST COPY c:\oracle\master~1.pdf c:\oracle\master.test
scott@10gXE> INSERT INTO test_tab VALUES (2, 'master.test')
  2  /
1 row created.
scott@10gXE> CREATE INDEX test_tab_idx ON test_tab (docs)
  2  INDEXTYPE IS CTXSYS.CONTEXT
  3  PARAMETERS
  4    ('DATASTORE test_datastore
  5        FILTER    CTXSYS.INSO_FILTER')
  6  /
Index created.
scott@10gXE> SELECT id FROM test_tab
  2  WHERE CONTAINS (docs, 'meat') > 0
  3  /
        ID                                                                     
         1                                                                     
         2                                                                     
scott@10gXE>