locally managed tablespace question

Fellow DBAs,

why is it that when I do a query on a temporary tablespace (TEMP) which is managed locally for the datafiles I get 0 rows returned, but when I run the same query on another locally managed tablespace, the datafiles return?

select file_name from dba_data_files where tablespace_name='TEMP'; 0 rows returned

select file_name from dba_data_files where tablespace_name='TB1'; /oracle/ora1/oradata/tb1.dbf

please copy tienp_at_wholefoods.com on your responses. Thanks.

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Phillip