RE: [xdi] Groups - Comments about XDI versioning (Draft-Contrib-OASIS-XDI-versioning.pdf) uploaded

[Giovanni Bartolomeo <giovanni.bartolomeo@uniroma2.it>]

Hello,

sorry I've been out for a while. Trying to summarize my understanding of
this interesting discussion..

> It would be great if somehow the
same mechanism could be used for "I have 5 versions" and
"I have 5 e-mail addresses".

I agree with this point, we should address both use cases in a
similar fashion.

>As you can see there are
the following two statements:
>=drummond/$has/$v   (this says that =drummond is
versioned)
>=drummond/$v/!5   (this says the current version is 5)
>I'd like to understand how you would do it instead.
>Would you say this?
>=drummond/$has$num$5/$v
>Or this?
>=drummond/$has$5/$v

My proposal is that $has could be used to specify cardinality, so
I would do like this:
=drummond/$has$5/$v

(applied to versioning as well as other composition/aggregation
relationships -btw here I think we've to discuss an issue: do we want to
model cardinality for composition and aggragation as well, e.g. $has$2
-> composition and $has$a$2 -> aggregation, sounds a bit
ugly!)

>=drummond/$has/$v   (this says that =drummond is
versioned)
>=drummond/$v/5   (this says the current version is 5)
>(=drummond/$v/5)/$is/!4

My idea is close to this one, except for the fact that I would use
$5 instead of 5 (is 5 a literal ("5")? in this case it should
be intended as parsed to an integer number, e.g. it would be an error a
statement like =drummond/$v/"5hg2" because "5hg2"
could not be parsed to an integer). Apart from this point, if I've
understood this correct, what I like most is that this way we decouple
document version (an index) from the place the document is stored;
example in java

Version vArr=Version[10];
System.out.println("v[2] memory address: 
"+vArr[2]);

v[2] memory address:  test.Person@4g7a2

here, @4g7a2 is a memory address similar to !4, whereas v[2] is an
element indexed by an integer number, like =drummond/$v/$5. This is one
of the reasons I would not use !5 and I prefer $5 instead.

BTW here it is not clear to me whether I've to use =drummond/$v/$5 or
=drummond$v$5, so far I've understood that the first one asserts that the
current version is version five, the second returns an xdi document
corresponding to that version, right?

>- I don't understand why I
would use the comparison operators like $greater in versioning..

I think this could be useful in a query, like the
following:

=Drummond$v/$greater/$4 

could return a composite document containing a list of =Drummond versions
starting from version five. 

What do you think?

Bests,
Giovanni


At 01.15 23/02/2008, Steven Churchill wrote:

 
Bill,
 
I gave my comment because there was a statement that the identifier =markus$v!1 would be inappropriate to identify an element in a “mutable” collection.
 
My point is that the notion of non-reassignability (persistence) here only applies to the last two subsegments – in this case that “$v“ namespace would not likely reassign the identifier “!1“ to something like “the concept of the real number pi”. Since the notion of persistence in “$v!1“ only applies to a convention in namespace “$v“ for it’s local child identifier “!1“, then the notion of persistence in “$v!1“ has no relevance as to whether =markus$v!1 is assigned to items in “mutable” or “non-mutable” collections. There is just no relationship between these concepts.
 
~ Steve
 
 

---

From: Barnhill, William [USA] [ mailto:barnhill_william@bah.com]
Sent: Friday, February 22, 2008 1:32 PM
To: Steven Churchill; Markus Sabadello
Cc: giovanni.bartolomeo@uniroma2.it; xdi@lists.oasis-open.org
Subject: RE: [xdi] Groups - Comments about XDI versioning (Draft-Contrib-OASIS-XDI-versioning.pdf) uploaded
 
 
Steve,
 
I apologize but do not have your background in graph theory. How does "
 
In summary, the convention that “$” is not going to reassign the local identifier “1” to “the concept of the real number pi” has nothing to do with assigning markus assigning the identifier =markus$v!1 to a mutable collection.
 
" apply?
 
I think you're suggesting our examples should be in the vein of =markus$v$1, is that correct?
 
Bill
 
 

---

From: Steven Churchill [ mailto:steven.churchill@xdi.org]
Sent: Friday, February 22, 2008 4:05 PM
To: 'Markus Sabadello'; Barnhill, William [USA]
Cc: giovanni.bartolomeo@uniroma2.it; xdi@lists.oasis-open.org
Subject: RE: [xdi] Groups - Comments about XDI versioning (Draft-Contrib-OASIS-XDI-versioning.pdf) uploaded
Reassignability is a convention that applies only at the XRI namespace level.
 
For example, an XRI namespace registry might do this:

1. Mint a new XRI authority (record) for a paying customer.
2. Assign it a local (bang) inumber to be returned as the final subsegment of it’s CID.

 
If the given XRI namespace registry is well-behaved, then it will follow the convention that it will not re-use the authority with the local inumber for another customer. (It won’t re-assign it to another customer.)
 
So, in this case, this notion of “not re-assigning” is a convention to be followed by well-behaved XRI namespace registries.
 
---
So what about the name space “$” and the child “1”. It would probably be a good convention that if “$” assigned the child authority named “1” to the concept of the integer value 1 then it shouldn’t at some later date assign  the local identifier to some other concept (like the real number pi, for example.)
 
---
 
In summary, the convention that “$” is not going to reassign the local identifier “1” to “the concept of the real number pi” has nothing to do with assigning markus assigning the identifier =markus$v!1 to a mutable collection.
 
~ Steve
 
 
 

---

From: markus.sabadello@gmail.com [ mailto:markus.sabadello@gmail.com] On Behalf Of Markus Sabadello
Sent: Friday, February 22, 2008 8:11 AM
To: Barnhill, William [USA]
Cc: giovanni.bartolomeo@uniroma2.it; xdi@lists.oasis-open.org
Subject: Re: [xdi] Groups - Comments about XDI versioning (Draft-Contrib-OASIS-XDI-versioning.pdf) uploaded
 
Hmm yes right, ! is persistent, so it doesn't work for mutable collections, I didn't think about that. If I have 5 e-mail addresses, one of them may get deleted. But in versioning persistence is what you want (version 2 will never change or go away..). So maybe the solution is to support both ! and *.

Versioning example (persistent):

=markus/$has!5/$v   <-- in the metagraph model, $has is for composite subjects, right? -->
=markus$v!1
  ...
=markus$v!2
  ..
=markus$v!3
  ..

Multiple e-mails example (reassignable):

=markus/$has$a*5/+email  <-- in the metagraph model, $has$a is for predicates, right? -->
    +email*1
        ..
    +email*2
        ..
    +email*3
        ..

Anyway, just a thought. It would be great if somehow the same mechanism could be used for "I have 5 versions" and "I have 5 e-mail addresses".

How would the +yesterday construct work? Would the endpoint look at timestamps on the individual version snapshots and find out which one to return?

Markus
On Fri, Feb 22, 2008 at 10:04 AM, Barnhill, William [USA] <barnhill_william@bah.com > wrote:
 

Hi guys,

You both have some very good and interesting points. Just saw this though and wanted to send off a thought: while ! syntax is easier to understand and read imho, it also might lead to a problem. If you are using it to things in a modifiable collection your collection order could change, or you could insert someplace other than the tail of the collection. This would mean you would need to reassign your ! identifiers, but are they reassignable? $n would get around that and lower the verbosity closer to ! level.

For versioning, I like best the following:


=drummond/$has/$v   (this says that =drummond is versioned)
=drummond/$v/5   (this says the current version is 5)
(=drummond/$v/5)/$is/!4

I think $v should by default be a # in the dictionary. If you want to access yesterday's last version you can do
=drummond/$v+yesterday
which accesses statements of the form
=drummond/$v+yesterday/5
(=drummond/$v/5)/$is/!4

What do you think?,
Bill


-----Original Message-----
From: markus.sabadello@gmail.com on behalf of Markus Sabadello
Sent: Thu 2/21/2008 10:45 PM
To: giovanni.bartolomeo@uniroma2.it
Cc: xdi@lists.oasis-open.org
Subject: Re: [xdi] Groups - Comments about XDI versioning (Draft-Contrib-OASIS-XDI-versioning.pdf) uploaded

Heya Giovanni,

Since I already tried to implement the versioning described in the XDI RDF Model v8 doc, it's interesting for me to read your comments about this..

- Regarding the use of $num instead of ! to index things, I think it's mostly a matter of taste. Both would work fine I think. One thought I am having is that subsegments like !1, !2, !3 do exist in XRI resolution too. I.e. there are some authority resolution servers that use these number-like subsegments (and not ip address-like subsegments like !203.173.1276.1663)..

- Regarding the number of versions, can I ask you something?

Maybe you can take a quick look at this URL: http://graceland.parityinc.net/xdi-endpoint/hibernate-graph-ver/=drummond
As you can see there are the following two statements:

=drummond/$has/$v   (this says that =drummond is versioned)
=drummond/$v/!5   (this says the current version is 5)

I'd like to understand how you would do it instead.

Would you say this?
=drummond/$has$num$5/$v

Or this?
=drummond/$has$5/$v

Just trying to understand it correctly.. I like the idea very much, it makes versioning a bit simpler and more consistent with other constructs..

Note to Drummond: We were talking about how to express multiple values of an attribute (e.g. =markus has multiple +email addresses). After reading Giovanni's comments, it appears to me that versioning may just be another instance of that same problem. I.e. there's no difference between saying =markus has 5 +email addresses, and saying that =drummond has 5 $v ersions. I agree with Giovanni that the same construct should be used in both cases.

- I don't understand why I would use the comparison operators like $greater in versioning.. What would be a practical use case for this? But in general I think these operators can be very useful..

Markus


On 14 Feb 2008 13:53:29 -0000, < giovanni.bartolomeo@uniroma2.it> wrote:


The document named Comments about  XDI versioning
(Draft-Contrib-OASIS-XDI-versioning.pdf) has been submitted by Giovanni
Bartolomeo to the OASIS XRI Data Interchange (XDI) TC document repository.

Document Description:
A first draft of comments on XDI versioning syntax

View Document Details:
http://www.oasis-open.org/apps/org/workgroup/xdi/document.php?document_id=27179

Download Document:
http://www.oasis-open.org/apps/org/workgroup/xdi/download.php/27179/Draft-Contrib-OASIS-XDI-versioning.pdf


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