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

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:] 

Sent: Friday, February 22, 2008 1:32 PM

To: Steven Churchill; Markus Sabadello

Cc: ; 

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:] 

Sent: Friday, February 22, 2008 4:05 PM

To: 'Markus Sabadello'; Barnhill, William [USA]

Cc: ; 

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:

Mint a new XRI authority (record) for a paying customer. 

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: 
[
mailto:] On Behalf Of Markus
Sabadello

Sent: Friday, February 22, 2008 8:11 AM

To: Barnhill, William [USA]

Cc: ; 

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]
<
> 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:

 on behalf of Markus Sabadello

Sent: Thu 2/21/2008 10:45 PM

To:



Cc:


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,
<
> 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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