Here is the sequence of events which occurs when you view a molecular
graphic in Chime. The last two steps below may be the ones you are most
- When you start up Netscape, it inventories all the plug-in
programs installed on your computer in Netscape's plug-ins directory, and
records their MIME (Multi-purpose Internet Mail Extension) types in an
internal table. You can view this table in Netscape by selecting Help,
- You view a web page which uses Chime. An <embed ...> tag in the
html document specifies either a source filename ending in .pdb,
.spt, or another Chime-supported file type. The html document
makes no explicit mention of Chime.
- Using its MIME table, the
web server looks up .pdb or .spt and serves the file as
MIME type chemical/x-pdb, chemical/x-spt, or another Chime-supported
- Netscape looks up the MIME type of the file in its internal plug-in
table and finds that it must run Chime.
- Chime is started up, creating a graphic area (usually black)
embedded on the web page, of the size specified in the html document.
Netscape hands the pdb, spt or other supported file to Chime.
- The atomic coordinate file (usually PDB) is sent from the server to
the client (your PC). It may be compressed with a program named
to save Internet transfer time. If so, it nevertheless has a name ending
in .pdb (although in fact it is no longer in PDB format), and is served
as chemical/x-pdb. When Chime receives it, Chime detects that it has been
gzipped and gunzips it automatically.
- Chime renders the image of the molecule. When you rotate
(etc.) the image, Chime creates each image de-novo from the atomic
coordinate file. The calculation of each image occurs entirely within
your PC, by Chime, which has the atomic coordinates stored in your
computer's memory. No Internet transfers occur while you are rotating
or otherwise modifying the molecular image. The images themselves are
never transferred through the Internet.
- When you click on a button, RasMol commands (also understood by Chime)
are sent to Chime, changing the image. If the commands are specified
within the web page html, no further Internet transfers are needed. If
the command script is contained in a file (name ending in .spt),
the server will transfer the command script file through the Internet to
your client PC's Netscape (unless it was referenced previously, sent, and cached).
Feedback to Eric Martz.