[WEB4LIB] Re: Subject: Re: In re includes

[Chris Zagar]

There is a subtle difference between files that have undergone SSI
processing and those that haven't.  When a web server sends a document,
one of the headers it can include specifies the date when the document was
last modified.  For a HTML file that has not undergone SSI processing,
this is the date when the file was actually last modified.  If a document
undergoes SSI processing, this header is normally omitted, since the
document has become dynamic.

So, why does that matter?  Well, proxy servers that obey the RFCs consider
the SSI processed files to be dynamic, and won't cache them.  This means
that changes you make to web pages are more likely to immediately
propogate out, without being aged by proxy servers, and that your log
files are more likely to log each and every hit made for your web pages,
which prevents all the otherwise proxy-served hits from being omitted from
your logs. Some downsides include the fact that browers will not be able
to use locally cached versions of files since the documents always
appeared modified, the inability to restart a large transfer of a really
large HTML file, and some confusion for your JavaScript if it tries to
access document properties like last modified date.

In most instances, none of this matters, but when it does, it can be quite
confusing if you don't know what's going on.

Chris

------------------------------------------------------------------------
Chris Zagar                                   Glendale Community College
Instructional Technologist                        6000 West Olive Avenue
zagar at gcinfo.gc.maricopa.edu                         Glendale, AZ  85302
http://gcinfo.gc.maricopa.edu/~zagar/                     (623) 845-3515