[sc34wg3] TMRM v6.0 comments

Nikita Ogievetsky sc34wg3@isotopicmaps.org
Tue, 26 Jul 2005 23:52:47 -0400

Hi Patrick,

Thank you for your comments.

! > 1)
! > Page 4:
! > "Proxies and their identifiers are interchangeable"
! > What does it mean and how can that be?
! > It contradicts with:
! > "Proxy is a set of finite set of properties" (p4)
! > "Subject proxies could have the same key/value pairs, but different
! > identifiers" (p9)
! >
! (The following is not entirely free from doubt or disagreement.)
! The problem arises because proxies in the most abstract sense are
! representatives of subjects and have no "identifiers."
! But, in order to do anything with proxies they have to be represented in
! an information system, which gives an instance of a proxy an identity
! vis-as-vis the system in which it is appearing. That identity does not
! have anything to do with the subject that it represents.
! In other words, in an information system, a proxy has two separate and
! distinct identities, 1. as a representative of a subject, and 2. as an
! addressable instance in the information system.
! I think (without having asked) that everyone would agree that a system
! identifier does not have any relationship to the subject that is being
! represented by a proxy. So, it appears to me that system identifiers
! should not be considered as a property of a subject proxy.
! But, it is equally true that being able to reference subject proxies by
! a system identifier is a very useful.
! The problem comes in, as you point out, what does it mean to say proxies
! are "identical?" If they have different system identifiers, then it
! seems the system regards them as distinct. (second sense of identity, as
! an addressable instance in the system) But if that system identifier is
! not a property of the proxy (and I don't think it should be) then it
! cannot serve to distinguish the proxies as per the definition of proxy
! in the TMRM. (first sense of "identity," i.e., the subject it represents)
! I would note that all this difficulty is caused by introducing the
! special case of all properties are identical, which is included in the
! general case of equivalence. (Newcomb pointed this out to me yesterday.)
! If we simply say that equivalence is declared by disclosures and leave
! the management of such cases up to disclosures, I think we would avoid
! some of the conceptual difficulty that you note in the current draft.
! That seems to answer any concerns about data redundancy (the reason for
! the "identical" properties statements) about as simply as it can be
! answered.

Thank you for clarifications I was also more trying to question whether it
is good to formulate it this way:
"Proxies and their identifiers are interchangeable"
Does it mean that if I replace all proxies with their identifiers I will not
loose information?
It seams that information is all in proxies, while identifiers are some
mechanical artifacts 

! > 2) Why introduce notion of "unordered sequence"? (p10)
! >
! > Instead of using old "set" or "bag"?
! >
! > Tastes like fat-free butter. :-) Or may be it is my English.
! >
! I would have to defer to Robert for a definitive answer. I suspect that
! "unordered sequence" is present simply to support the notion of "ordered
! sequence."
! Bags can be ordered or unordered so it may simply be multiplying terms. ;-
! )

Yes, I understand that. My question was to the naming convention:
Sequence by definition is an "ordered set". 
So "unordered sequence" = "unordered ordered set"

"- A following of one thing after another; succession. 
- An order of succession; an arrangement. 
- A related or continuous series. See Synonyms at series. 
- Games. Three or more playing cards in consecutive order; a run. 
- A series of related shots that constitute a complete unit of action in a
- Music. A melodic or harmonic pattern successively repeated at different
pitches with or without a key change. 
Mathematics. An ordered set of quantities, 
[...] "

--The American HeritageR Dictionary of the English Language, Fourth Edition

I would stick with sets, why use other terms?