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Document domain root
IPS server file layout matches the domain name, but in reverse. With this it is possible to find a filepath to files on other virtual servers as long as they are hosted on the same machine. in this scheme, 'subdomain.example.com' would have directories thus: .../com/example/subdomain. Whether it's a symlink or an actual directory the best way to do this is a /www/ partition which would yield, in this example: /www/com/example/subdomain.
By this method it is predictable and computable where any file for any domain is on this physical server, and sites on the same server can share assets "behind the scenes". In this context the system uses it to find thumbnails of photos and to find Base 64 versions (for inline delivery) of these thumbnails.
This is all well and good in a heterogeneous domain environment where every domain is example.com or example.net or example.org or example diot any-tld. But, since this system has to work for any domains this must include "tlds" such as palo-alto.ca.us; the dcomplication arises when a virtual host has more than one name. Thus, as well as a virtual webserver that appears from the "outside" to be the same must also look the same on the "inside". That is, filepath to each of the virtual serves must be made to work with symlinks. This if example.com is the name of the website but it lives on the server is /www/ca/us/palo-alto/example, then symlinks my be provided of the form /www/com/example must be inserted so files on /www/us/ca/palo-alto/example can also be accessed via /www/com/example.
This is computed by mkdirutils/find_local_variant
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img ref and img thumb
When an icon is used for a directory a symbolic link is written. This is of the form:
- for any directory with an icon for a subdirectory: ...url/dir-parent/subdirN>
- then a link will be written in dir1 of the form .subdirN.img.ref
- additionally, a link to a thumnail version is creater of the form: subdirN.img.thumb
- finally a link is written of the form .<subdirN>.thumb that points to one or the other of the two thumbnails, anf option that can be selected in the
edx small options screen
There are a few uses for this.
- First it can be used by programs other than the one that wrote it. Thus, when edx finds a viable thumbnail it provides this information as a link; when
index runs and needs a thumbnail for the menu icons ("bubble menu") than it derives it via this mechanism.
- Second, it can be used by people to address an image that is used as a icon for a subdir. For example is had a page that had types of cats say: the 'cats' directory has subdirs for tiger, house cat, lion, puma etc, and if you wanted to use a reference photo of a tiger, than you could use the expression (url)../cats/.tiger.img.ref as a known predictable image. The caveat is, the image could change if it is moved or deleted which is rare, more likely the image is upgraded. Therefor by this level of indirection a link to an image can be used which will or should get better over time.
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metrics and logic
Thumbnails are key to the IPS system. This section explains the metrics and logic used by the system.
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