Discussion of Internet addressing
Email addresses
user@domain
user@subdomain
like:
user@dcu.ie
user@computing.dcu.ie
Case irrelevant.
Any "." to the LHS:
name.surname@computing.dcu.ie
are just cosmetic.
They do not represent subdivisions, as "." to the RHS does.
Site can implement any naming scheme it likes on LHS of the @ sign.
Web addresses (URLs)
http://hostname/path
http://hostname/directory/subdirectory/file.html
http://hostname/~user/directory/subdirectory/file.html
Path may map 1-1 to actual path on disk.
Or may not:
- database request
- content management system
- result of running server-side program
Case irrelevant in the http: part
and the hostname part.
Case may be relevant in the path part only.
e.g. UNIX server maps 1-1 with file on disk and respects case.
Windows server doesn't.
Computing (CA) server
CA server is
case-sensitive username.
My name lowercase redirects to my site:
https://www.computing.dcu.ie/~humphrys/
Other case name not found:
https://www.computing.dcu.ie/~Humphrys/
Internet addresses v. postal / phone addresses
Internet addresses seem to have a number of advantages over
postal addresses or telephone numbers.
Internet addressing is:
- Alphanumeric, allowing direct maps to English.
As opposed to numeric-only addresses
like phone numbers.
(An ad says something like:
"14172 - Your new mobile
directory enquiries
number.
The only number you'll ever need."
How is anybody to remember something like that?
Especially when it changes every couple of years.)
Be careful about imposing all-numeric or other cryptic solutions on your users.
When I was a postgrad, I was given the userid
mh10006
- despite the fact that the userid
humphrys
was unused and available.
Why increase login failures, failed emails, and 404 Not Found web requests
for no reason?
It is interesting to consider that underneath,
Internet addressing is actually numeric,
but machines have been forced to map
text strings to numbers
since the earliest days of the Internet.
- Guessable. I know IBM's web site is ibm.com.
I have no idea what their phone number is,
and if told I wouldn't remember anyway.
I don't even know what DCU's phone number is,
and I work for them.
Maybe I could remember IBM's phone number
if it was 1-800-IBM-CORP.
Or does that 1-800 number only work in America?
Or should it be 1-800-BUY-IBM?
Who knows.
And what is their postal address?
I don't know, but I know I'll find all that information
at ibm.com.
- Variable-length.
Your company's website is simply company.com,
whether that means
bt.com
or
arthurandersen.com.
It doesn't have to be either squashed into a small number of characters,
or expanded to fit a fixed-size field, as with say 1-800 numbers.
Note that some older competing naming schemes weren't as flexible,
e.g. BITNET had maximum 8 char names.
- Location independent,
so don't have to memorise loads of area codes.
You bookmark
www.site.co.uk/subsite
and the bookmark works, whether you are in the UK,
in Ireland, or anywhere at all in the world.
Note that you couldn't set up links for other people
if it wasn't location independent.
Quick!
What's the area code for Belfast?
What's the area code for London?
- Hierarchical, so we can get to dcu.ie safely and then start
looking for the Computer Dept.
Addresses often contain a self-description
of their place in the hierarchy:
comp-dept.western-university.edu.au/staff/dr.smith/phd/references.html
- We can also get repeated feedback in our guesses,
e.g.
dcu.ie/user
failed, so we try
dcu.ie
Now we've got to the dcu.ie
web home page safely,
we can use this as a base from which to explore further
and hopefully find a link to
user
Dial a wrong number and what's your feedback?
Post a letter to the wrong address and what's your feedback?
Bad - UNIX usernames
Historically, one area where UNIX/Linux
fell down was on usernames.
Long and variable-length filenames
were ok,
but usernames were restricted to 8 chars.
The legacy of this is still with us.
e.g. The UNIX and Linux systems here actually allow long usernames,
but the log files and other administration tools
only display the first 8 chars
- which is why student usernames are still ugly and squashed.
- useradd
says Linux usernames may be 32 characters long.
-
But you will notice usernames on DCU Linux are limited to 8 chars.
Can we make the phone system like the Web?
We want a phone number system
where we can make location-independent links to calls.
If you have a smartphone,
or a device with pay-to-call VoIP like
Skype,
you can do this.
callto
Put the following in your HTML:
tel
Automatic number recognition
Maybe
no need to have page authors make the number a link.
Do automatic number recognition instead.
- Browse page on phone. Select a number on a page.
Recognition software tries to dial it.
-
On PC,
Skype Toolbar
automatically makes clickable any phone number seen on screen
in browser:
Note how it does not highlight the fax no. Clever.
Old - WAP links
You could set up the following links in the old
mobile phone protocol
WAP.
(Though few did, because few people browsed the web on WAP.)
There is a location independent tag
WTAI
(also here)
in WAP.
Future - DNS system for phones
Might be nice to get rid of (or reduce) the numeric part of the phone numbers:
callto:7008059@1.353
callto:7008059@1.ie
callto:7008059@dublin.ie
callto:8059@700.dublin.ie
callto:8059@dcu.dublin.ie
callto:humphrys@dcu.dublin.ie
callto:ca@dcu.dublin.ie
callto:dcu@dublin.ie
callto:12345678@london.uk
Would require the implementation of a name server (DNS) system for phones.
Downside:
Need to print two different forms of the phone number on your page.
One for callers with access to DNS.
One for callers with phone-only.
Ancient Brain