RE: [topicmapmail] RE: some more RDF thoughts

From: W.M. Jaworski <wmj@gen-strategies.com> · Date: Mon, 25 Jun 2001 04:45:24 -0400

[Graham Moore]
Could someone explain / illustrate the meaning of '(Ra,Rb,Rc)' in the
context of:
'Enhancing (a,b,c) RDF schema by (Ra,Rb,Rc) role triple will eliminate
ambiguity and give'

[wmj]
I am pleased that you did notice my deliberate 'cheating' by dealing only
with "Solution 1. from Lars". I just wanted to signal a 'mismatch' between
RDF, NL interpretation and TopicMap.

Single 3-tuple can deliver only limited "load" of semantics. Therefore, to
deliver more semantics, requires couple (or more!) of the 3-tuples or more
expressive construct.

"(1) For every "Creator" predicate, the subject is an addressable
  resource, of which the object is an occurrence value of the type
  "Creator"".

Role-oriented interpretation:
RDF 3-tuple: (http://www.w3.org/Home/Lassila, Creator, Ora Lassila)
Roles 3-tuple: (addressable resource, type, occurrence value)

"(2) For every "Creator" predicate, the subject is an addressable
  resource, while the object is the name of a topic of type
  "Person". The relationship between them is that there is an
  association of type "created-by" between them, with the subject
  playing the role "resource" and the object the role "creator"."

Role-oriented interpretation:

RDF 3-tuple: (http://www.w3.org/Home/Lassila, Creator, Ora Lassila)
Roles 3-tuple: (addressable resource, "Creator", "Person")
Roles 3-tuple: (addressable resource, "created-by", "Creator")

'Re-written' as an Enhanced Spreadsheet ('more expressive construct'):
A	A	{Context}
v		Solution 1
	v	Solution 2
F	F	{NODE}
f	f	http://www.w3.org/Home/Lassila
t	t	Ora Lassila
N	N	{ROLE}
f	f	addressable resource
t		occurrence value
	t	"Creator"
	t	"Person"
E	E	{ASSOCIATION}
m		type
	m	"created-by"

Column 3 lists atoms clustered into sets. Column 1 (or 2) maps the atoms
into "the full semantic of the relationship" for the Solution 1 (or 2).

Graphical interpretation of the relationship:
From_Node--Arrow_Tail----Arrow_Middle--Arrow_Head--To_Node
where each component of the relationship could be 'overloaded'.

I hope this helps.

WMJ

-----Original Message-----
From: Graham Moore [mailto:gdm@empolis.co.uk]
Sent: Monday, June 25, 2001 2:13 AM
To: 'W.M. Jaworski'; 'Lars Marius Garshol'; 'Peter Breton'
Cc: 'Topicmapmail'; dspace-code@MIT.EDU; 'www-rdf-dspace'
Subject: RE: [topicmapmail] RE: some more RDF thoughts

The description below (2) is what I was aiming at in the RDF paper presented
in Berlin. At the time I tried to describe this semantic model mapping
without using RDF schema. I wanted to be able to go from RDF to TopicMaps
without additional schemering required. Solution 1. from Lars allows this
but may not always capture the full semantic of the relationship.

The proposal to use the RDF schema to fill in the missing 'template' gaps
i.e. the nature of the roles that the topics play, seems like its is
necessary to solve the problem.

(2) For every "Creator" predicate, the subject is an addressable
  resource, while the object is the name of a topic of type
  "Person". The relationship between them is that there is an
  association of type "created-by" between them, with the subject
  playing the role "resource" and the object the role "creator"."

I like the first model that Lars decribes - but feel that the one above is
more powerful. i.e topic occurrences can be/ are topic associations therefor
the more general model is the association.

Could someone explain / illustrate the meaning of '(Ra,Rb,Rc)' in the
context of:

'Enhancing (a,b,c) RDF schema by (Ra,Rb,Rc) role triple will eliminate
ambiguity and give'

I'm assuming its a little like a TopicMap template

<templateid>, (<role-defining-topic>, <class-of-role-playing topic>)*)

except is there a 'class of role playing topic'?

e.g - these are topicRefs or abouts in RDF.

(creates, (creator , person), (created-thing, ANY/topic/resource)

I gather from the note on the double store that this would be to connect
'instances' to 'templates' / 'schema' definitions.

What is the reason for the second store? Is it just organisational?

cheers

graham

-----Original Message-----
From: topicmapmail-admin@infoloom.com
[mailto:topicmapmail-admin@infoloom.com]On Behalf Of W.M. Jaworski
Sent: 23 June 2001 07:29
To: Lars Marius Garshol; Peter Breton
Cc: Topicmapmail; dspace-code@MIT.EDU; www-rdf-dspace
Subject: [topicmapmail] RE: some more RDF thoughts

[Peter Breton]
Umm, yes they do, as does a filesystem, once you solve the "trivial"
problem of mapping your data into flat files. :)
What I meant is that you store all the data in the same way, without
defining new schemata for them
..............

[wmj]
Using the "trivial" schema of RDF to "store all the data in the same way" is
creating the "non-trivial" problem of harvesting meaning from the triple
store. Here are two interpretation of the following RDF statement
(http://www.w3.org/Home/Lassila, Creator, Ora Lassila) provided by Lars
Marius Garshol in a recent e-mail to the topicmapmail forum:

"(1) For every "Creator" predicate, the subject is an addressable
  resource, of which the object is an occurrence value of the type
  "Creator".
(2) For every "Creator" predicate, the subject is an addressable
  resource, while the object is the name of a topic of type
  "Person". The relationship between them is that there is an
  association of type "created-by" between them, with the subject
  playing the role "resource" and the object the role "creator"."

Enhancing (a,b,c) RDF schema by (Ra,Rb,Rc) role triple will eliminate
ambiguity and give

(http://www.w3.org/Home/Lassila, Creator, Ora Lassila)
(addressable resource, type, occurrence value)

[Peter Breton]
One possibility running through my head is a "double triple store".

[wmj]
Any comments for my version of a "double triple store"? :-)

Best

WMJ

-----Original Message-----
From: www-rdf-dspace-request@w3.org
[mailto:www-rdf-dspace-request@w3.org]On Behalf Of Peter Breton
Sent: Friday, June 22, 2001 1:13 PM
To: W.M. Jaworski
Cc: www-rdf-dspace; dspace-code@MIT.EDU
Subject: Re: some more RDF thoughts

>[Peter Breton]
>The beauty of the triple store mechanism is that you can accomodate ALL
>the data in it.
>
>[wmj]
>Other store mechanisms (for example relational) also "accomodate ALL
>the data in it."
>
Umm, yes they do, as does a filesystem, once you solve the "trivial"
problem of mapping your data into flat files. :)

What I meant is that you store all the data in the same way, without
defining new schemata for them, thus finessing the problem that the
Associative Model of Data paper describes:

"Under the relational model, every table is structured differently that
is, it has different columns and column headings and the programs are
designed around the tables. It is impossible to write an efficient
program that is capable of accessing a table whose structure is not
known when the program is written, just as it is impossible to make a
key that will open any lock."

(However, I believe that in the physical world there are, in fact, keys
that open any lock :)

>[Peter Breton]
>the roundtrips from client/middleware to RDBMS are likely to be some of the
>most expensive operations
>
>[wmj]
>If the 'client/middleware' is not RDF, than is it another notation? Is RDF
>notation a technology looking for the applications?
>
The client/middleware that I was envisioning in this case is some kind
of RDF-to-RDBMS engine. Given that this fit is somewhat unnatural, it
seems that moving it closer to the RDBMS can only help its efficiency.

(At the moment, I think RDF is in fact looking for applications.....)

>[Peter Breton]
>3) Another road: since queries on an unbounded triple store ....
>
>[wmj]
>It seems that the problem is solved by "Associative Model of Data^(TM) -
>http://www.lazysoftware.com
>
Thanks for the pointer. I will check them out.

>BTW I am not an opponent of RDF, I am an outsider looking for insights and
>knowledge.
>
Likewise! :-)

Peter

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