The meaning of the first three optional parameters is exactly the same as in the Allow command.
When processing a document with the URL
matching pattern, indexer downloads only a
little part of the document and tries to find
MP3 tags in it.
On success, indexer parses MP3 tags, otherwise it downloads
the rest of the document and parses it as usual, according
to the Content-Type HTTP response header.
Note: CheckMP3 works only with servers supporting HTTP/1.1 protocol. It uses the "Range: bytes" HTTP request header to download MP3 tags.
Indexing MP3 files is explained in details in the Section called Creating an MP3 search engine in Chapter 6.