W3C home > Mailing lists > Public > public-credentials@w3.org > May 2016

Re: Updated data model specification document

From: Steven Rowat <steven_rowat@sunshine.net>
Date: Sun, 29 May 2016 10:48:20 -0700
To: public-credentials@w3.org, Dave Longley <dlongley@digitalbazaar.com>
Message-ID: <8fa3bfce-e795-e952-2b4d-e081dc4f68a3@sunshine.net>
On 5/28/16 7:55 PM, Dave Longley wrote:
> On 05/28/2016 01:28 PM, Steven Rowat wrote:
>>
>> I may misunderstand the overall VC data model at some other level, but
>> in the way I'm attempting to understand it, 'property' seems misleading,
>> if being used to denote a relationship between two 'things' or 'nodes'.
>> To follow common English usage, the 'property' should belong to either
>> the subject node, or the object node, not designate the relation between
>> them.
>
> You can still think of it that way, it's not incompatible. For example,
> "favoriteColor" and "name" are properties that belong to a particular
> entity. Those properties have values associated with them. Together, you
> can make two statements:
>
> Entity X has a name Y.
> Entity X has a favorite color Z.
>
> That doesn't change the data model to think of it that way. You're both
> asserting that entity X has some properties -- and that those properties
> can be thought of as relations between entity X and other literals or
> entities, Y and Z.

Hmm...maybe it would be useful to explain this (at least to myself), 
in terms of traditional set theory, and/or measurements from within a 
limited continuum.

What I mean is that any general property could equally be described as 
a set of similar items, and we label this set -- in your examples 
above -- 'name' or 'color', and then choose or measure instances from 
it, which become the 'object' in the triple; and we associate these 
with the 'subject' of the triple -- which, combined with the set 
itself, is what makes the whole triple.

In terms of your examples, for the 'name' property we would call it 
the 'set of all names', with instance Y that's associated with Entity 
X -- forming the triple that might be expressed as:

Entity X is associated with Instance Y, [which is chosen from the set 
(property) of all Names]

or, to keep the traditional triple sequence, and closer to actual 
real-world sequence of events:

Starting with Entity X -> search among set [property] of all Names -> 
associate Name Y

And in the VC data model, each of Entity X, Names, and Y, are given 
distinct IDs.

And any of the three positions could be either a literal (instance, 
measurement from within a set/property) or a whole set.

Does this seem an accurate way of understanding the architecture?

Steven


>
>>
>>> The value for "id" may be a URL that globally
>>> identifies the subject. Every other property defines a relation between
>>> the subject and an object.
>>
>> Same concern as above. Of course you could redefine the word
>> 'property'--and perhaps you have--to mean 'relationship' in the specific
>> context of the VC data model, but it seems counter-intuitive to do this
>> (since the wider world doesn't use it this way) unless unless there's a
>> special reason (which I'm not understanding yet) as to why this
>> redefinition is appropriate.
>>
>> If there is such a reason, I'd really really like to know what it is.
>> :-) :-)
>
> Well, I'd argue that using the term "property" is well established in
> technology circles as referring to members of a particular class, keys
> (or key-value pairs) in JSON, and as a synonym for "predicate" in RDF.
> So we expect it's usage to be familiar to both Web developers and
> people who use data models like RDF. I think we stand to gain support
> and general understanding from both groups by using this terminology.
>
>>
>>
>> Steven
>>
>> p.s. Sometimes a simple-as-possible block flow-diagram is the best way
>> to get the basic architecture across. Is it possible someone could make
>> one of those for the VC data model?
>>
>
> A good idea.
>
>
Received on Sunday, 29 May 2016 17:48:45 UTC

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