In the beginning (RSS 0.92), RSS carried attached files (such as MP3 files) to RSS readers through a mechanism called enclosure tags. While most podcast listeners will use one of the podcast clients such as iPodder or iTunes to subscribe to your podcast, you should be prepared for those who are still using an RSS news reader. For them, let's talk about enclosure tags. An enclosure tag is one of the optional elements that exists in RSS 2.0. Like so many elements, it provides a way to describe pieces of information beyond the basics of a story link and channel description. <enclosure> is an optional subelement of <item>. Looking back at Listing 9.1, the enclosure tag should be inserted just before the </item> tag for each episode of the podcast. The enclosure tag has three required attributes. "url" is the location of the enclosure, "length" is the file length (in bytes), and "type" is the type of file it is, expressed as one of the standard MIME types. <enclosure url="http://www.ABG2Podcasting.com/mp3s/EarlyPodcast.mp3" length="18218340" type="audio/mpeg" /> The list of standard MIME types shown in Table 9.1 shows that enclosure tags can be used for more than just podcasts, but for most podcasters it will be enough to know that they can be used to allow a listener who's committed to an RSS news reader to subscribe to, and receive, the podcast. You should understand that not every RSS news reader can handle enclosures such as podcasts, but while the computer industry is still trying to figure out how to build support for RSS (and all its related media types) into operating systems and applications, a version of your RSS feed with enclosure tags may expand the potential audience for your podcast. Table 9.1. Mime File Types Cover Far More Than Just Audioai | application/postscript | aif | audio/x-aiff | aifc | audio/x-aiff | aiff | audio/x-aiff | asc | text/plain | au | audio/basic | avi | video/x-msvideo | bcpio | application/x-bcpio | bin | application/octet-stream | c | text/plain | cc | text/plain | ccad | application/clariscad | cdf | application/x-netcdf | class | application/octet-stream | cpio | application/x-cpio | cpt | application/mac-compactpro | csh | application/x-csh | css | text/css | dcr | application/x-director | dir | application/x-director | dms | application/octet-stream | doc | application/msword | drw | application/drafting | dvi | application/x-dvi | dwg | application/acad | dxf | application/dxf | dxr | application/x-director | eps | application/postscript | etx | text/x-setext | exe | application/octet-stream | ez | application/andrew-inset | f | text/plain | f90 | text/plain | fli | video/x-fli | gif | image/gif | gtar | application/x-gtar | gz | application/x-gzip | h | text/plain | hdf | application/x-hdf | hh | text/plain | hqx | application/mac-binhex40 | htm | text/html | html | text/html | ice | x-conference/x-cooltalk | ief | image/ief | iges | model/iges | igs | model/iges | ips | application/x-ipscript | ipx | application/x-ipix | jpe | image/jpeg | jpeg | image/jpeg | jpg | image/jpeg | js | application/x-javascript | kar | audio/midi | latex | application/x-latex | lha | application/octet-stream | lsp | application/x-lisp | lzh | application/octet-stream | m | text/plain | man | application/x-troff-man | me | application/x-troff-me | mesh | model/mesh | mid | audio/midi | midi | audio/midi | mif | application/vnd.mif | mime | www/mime | mov | video/quicktime | movie | video/x-sgi-movie | mp2 | audio/mpeg | mp3 | audio/mpeg | mpe | video/mpeg | mpeg | video/mpeg | mpg | video/mpeg | mpga | audio/mpeg | ms | application/x-troff-ms | msh | model/mesh | nc | application/x-netcdf | oda | application/oda | pbm | image/x-portable-bitmap | pdb | chemical/x-pdb | pdf | application/pdf | pgm | image/x-portable-graymap | pgn | application/x-chess-pgn | png | image/png | pnm | image/x-portable-anymap | pot | application/mspowerpoint | ppm | image/x-portable-pixmap | pps | application/mspowerpoint | ppt | application/mspowerpoint | ppz | application/mspowerpoint | pre | application/x-freelance | prt | application/pro_eng | ps | application/postscript | qt | video/quicktime | ra | audio/x-realaudio | ram | audio/x-pn-realaudio | ras | image/cmu-raster | rgb | image/x-rgb | rm | audio/x-pn-realaudio | roff | application/x-troff | rpm | audio/x-pn-realaudio-plugin | rtf | text/rtf | rtx | text/richtext | scm | application/x-lotusscreencam | set | application/set | sgm | text/sgml | sgml | text/sgml | sh | application/x-sh | shar | application/x-shar | silo | model/mesh | sit | application/x-stuffit | skd | application/x-koan | skm | application/x-koan | skp | application/x-koan | skt | application/x-koan | smi | application/smil | smil | application/smil | snd | audio/basic | sol | application/solids | spl | application/x-futuresplash | src | application/x-wais-source | step | application/STEP | stl | application/SLA | stp | application/STEP | sv4cpio | application/x-sv4cpio | sv4crc | application/x-sv4crc | swf | application/x-shockwave-flash | t | application/x-troff | tar | application/x-tar | tcl | application/x-tcl | tex | application/x-tex | texi | application/x-texinfo | texinfo | application/x-texinfo | tif | image/tiff | tiff | image/tiff | tr | application/x-troff | tsi | audio/TSP-audio | tsp | application/dsptype | tsv | text/tab-separated-values | txt | text/plain | unv | application/i-deas | ustar | application/x-ustar | vcd | application/x-cdlink | vda | application/vda | viv | video/vnd.vivo | vivo | video/vnd.vivo | vrml | model/vrml | wav | audio/x-wav | wrl | model/vrml | xbm | image/x-xbitmap | xlc | application/vnd.ms-excel | xll | application/vnd.ms-excel | xlm | application/vnd.ms-excel | xls | application/vnd.ms-excel | xlw | application/vnd.ms-excel | xml | text/xml | xpm | image/x-xpixmap | xwd | image/x-xwindowdump | xyz | chemical/x-pdb | zip | application/zip |
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