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Subject: $n (was Re: again on numbering..)



In reviewing this thread, I was struck that “$num” is such a fundamental concept that it really falls under the same rule the XRI TC originally established, which that fundamental identifier spaces deserve single-letter XRIs for brevity and universality. For example:


            $d --> datetime

            $l --> language/locale

            $v --> version


Therefore I would like to propose that we shorten “$num” to “$n”, especially given that the variable name “n” is frequently given for the concept of “number”.


I have noted this option on the DollarWord page:




I’ll put this on the agenda for tomorrow’s telecon.




From: Giovanni Bartolomeo [mailto:giovanni.bartolomeo@uniroma2.it]
Sent: Monday, February 11, 2008 2:44 AM
To: Markus Sabadello
Cc: xdi@lists.oasis-open.org; Drummond Reed
Subject: [xdi] Re: again on numbering..


Hello Markus,

2) Hmm yes I think I understand the difference.. But I think concatenating the subject and predicate the way you do it (=markus+email/$num$1/" markus.sabadello@gmail.com") could cause trouble, because how are you supposed to know later that +email is an attribute of =markus. I think the "list" situation, in which you have multiple values for an attribute, should look as similar as possible to the "normal" situation, in which you have just one value for the attribute.

I think I guessed what you mean, but I'm not sure... could you make an example? In any case,  what about to use this alternative form:

=markus+email$1/$type$xsd$string/" markus.sabadello@gmail.com"

which sounds solid, as it keeps the advantage of avoid to semantically overload "!", is compliant with my original idea about the usage of $num notation, and should not cause the troubles you mentioned (if my guess was corrent), as $ is a subcontext refereing to =markus+email... What do you think?

Looking forward!

On 1/31/08, Giovanni Bartolomeo < giovanni.bartolomeo@uniroma2.it> wrote:

Hello again!

I see this could be a solution as well, however, I would like share with you some thoughts:

1)  The use of "!" (bang) was originally designed to be similar to the use of "ip addesses" (maybe I'm getting wrong here, in case please correct me :-), so thinks like !203.173.1276.1663 were permitted. This is obviously a misleading semantics as " !203.173.1276.1663" is more an identifier than a number. What do you think?

2) Actually, I see a slightly different meaning for the two statements:

=markus/+email!1/" markus.sabadello@gmail.com"


=markus+email/$num$1/" markus.sabadello@gmail.com"

Try to explain my concern (that's a bit hard!).

In the first statement, it's like as the concept +email in itself has subspaces for !1, !2, etc. As far as I've understood, by concatenating two subsegments the second one assumes a meaning related to the first one, so it's like to have the email, taken as concept (+email), having some multiplicity in its own.

In the second statement, instead, we just use $num an integer in order to index one of the +email attributes kept by =markus, which exist because they've been explicitly declared as such (Markus' attributes). They wouldn't exist otherwise.

It's somehow like the java statements:

Person markus;

markus.email=new Email[] {" markus.sabadello@gmail.com "," markus.sabadello@xdi.org"};

Email selectedMail=markus.email[1];

But maybe I'm getting wrong here as well, so you comments will be more than welcome! (and sorry if maybe it sounds a bit too "philosophic"!)



At 18.41 29/01/2008, Markus Sabadello wrote:

Heya Giovanni,


I think the idea of having a way to express ordered collections in XDI would be very useful...


We came across a similar problem a few days ago.. How do we express multiple values for a predicate? For example, =markus could have multiple e-mail addresses. We came up with the following idea:


=markus/+email!1/" markus.sabadello@gmail.com"

=markus/+email!2/" markus.sabadello@xdi.org"


But your pattern would work too:


=markus+email/$num$1/" markus.sabadello@gmail.com"

=markus+email/$num$2/" markus.sabadello@xdi.org"


A third idea Drummond had was to use inner graphs, like this:







                    " markus.sabadello@gmail.com"


                    " markus.sabadello@xdi.org"


I like all three methods.. But we should probably decide on one of them.. Or just experiment for a while and see what works best...




On 1/29/08, Giovanni Bartolomeo < giovanni.bartolomeo@uniroma2.it> wrote:


some new inputs about this issue:

>* Markus asked if $num is always used in conjuntion with $has predicate, or

>if there would be other uses? Giovanni said it would also be useful


I think that $num could be useful also in accessing arrays, vectors

and similar structures what we could call "ordered collections".

Let's consider again this use case:



we could index each player using $num${x} as follow:







Do you think this capability could be of help for XDI?

BTW maybe we can avoid the prefix $num and leave only ${num}, e.g.

$0, $5, $7 are valid XRIs which represent the number 0, 5, 7.

What do you think?




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