Forum OpenACS Q&A: understanding paths and structure

I've playing around on my website and I can't understand how the css files are included on the pages.

For example:

On the adp file, "site-master-kelp.adp" which is located in "/home/yabtdev/yabtdev/www/"
i have the variable:@css_url@
link rel="stylesheet" type="text/css" href="@css_url@" media="all"

On the respective tcl page "site-master-kelp.tcl", located in the same folder "/home/yabtdev/yabtdev/www/"
i have this include call:
set css_url "/resources/acs-subsite/site-master.css"

But the file "site-master.css" is located on:
"/home/yabtdev/yabtdev/packages/acs-subsite/www/resources/site-master.css"

and the thing is that the folder "/acs-subsite/" bellow /resources/ doesn't even exist.

In my view it should be like this:
set css_url "/packages/acs-subsite/www/resources/site-master.css"

Since the root folder is "/home/yabtdev/yabtev/"

Another example:

on the file: "dotlrn-master-kelp.adp" located in "/home/yabtdev/yabtdev/packages/dotlrn/www/"

I have the tag
link rel="stylesheet" type="text/css" href="/resources/dotlrn/dotlrn-master-kelp.css" media="all"

and the file "dotlrn-master-kelp.css" is located on
/home/yabtdev/yabtdev/packages/dotlrn/www/resources/dotlrn-master-kelp.css

but the folder /dotlrn/ bellow /resources/ doesn't even exist.
In my view the right path should be
link rel="stylesheet" type="text/css" href="/packages/dotlrn/www/resources/dotlrn-master-kelp.css" media="all"

So what does the tcl code do to recognize and find the file on the exactly folder?
What is the logical sense to these files being included?

That's weird!
Do you know the reason of this?
Why is it "structurized" like that?

I don't understand TCL at all!! :)

I barely understood what you meant. I'm sure it's because i'm not that furhter on oacs yet. I just need more time.
What about the requests those don't use the database, even permissons, like the second one that is only on the adp file. and it seems to be inverted

**********************
on the file: "dotlrn-master-kelp.adp" located in "/home/yabtdev/yabtdev/packages/dotlrn/www/"

I have the tag
link rel="stylesheet" type="text/css" href="/resources/dotlrn/dotlrn-master-kelp.css" media="all"

and the file "dotlrn-master-kelp.css" is located on
/home/yabtdev/yabtdev/packages/dotlrn/www/resources/dotlrn-master-kelp.css

but the folder /dotlrn/ bellow /resources/ doesn't even exist.
In my view the right path should be
link rel="stylesheet" type="text/css" href="/packages/dotlrn/www/resources/dotlrn-master-kelp.css" media="all"
************************************

I've read the page "packages/acs-tcl/tcl/request-processor-procs.tcl". I could understand some points but It's still sort of chinese to me. =)

ad_proc -private rp_resources_filter { why } {

This filter runs on all URLs of the form /resources/*. The acs-resources package
mounts itself at /resources but we short circuit references here in order to
maximize throughput for resource files. We just ns_returnfile the file, no
permissions are checked, the ad_conn structure is not initialized, etc.

There are two mapping possibilities:

/resources/package-key/* maps to root/packages/package-key/www/resources/*

*******************8
" Keep in mind that if you do an internal redirect to something other than
the current directory, relative links returned to the clients
browser may be broken (since the client will have the original URL).""

I understood "internal redirect" as if i try to include pages those are "i don't knnow" or if the pages needs permission. Is that correct?

Another thing is...
I couldn't match this with the header metatags. I mean, how do they go to the final page, on the client side(i.e. on the user's browse). Can you tell how they go to the page? Where are the metatags actually located?

I want to track and debug the whole process that it takes since the begining(i.e. the first step) to the end(i.e. user's browser).