Feed on
Posts
Comments

The ‘meaning’ of an identifier

Mar 2nd, 2006 by Phil Dawes

Here’s an attempt at a working definition:

The ‘meaning’ of an identifier = the complete set of assertions that can be made about it.

(for the purpose of discussion of identity in information systems).

E.g. if an assertion is true for one identifier but not another, then they don’t mean (or denote) the same thing.

Does that sound reasonable?

Posted in General, Semantic Web | Comments

Viewing 6 Comments

    • ^
    • v
    What do we mean by an assertion being true? Is an assertion "true" if it is published?

    Consider http://www.whitehouse.gov/president/gwbbio.html
    as an identifier. What assertions are true of it?
    • ^
    • v
    Hi Tim!

    What do we mean by an assertion being true?
    Exactly that.
    Consider http://www.whitehouse.gov/president/gwbbio.html
    as an identifier. What assertions are true of it?

    It depends on what the identifier denotes - i.e. 'means'. This is the connection I'm trying to make - the meaning of the identifier is the set of assertions that are true of it.

    Does that make sense?
    • ^
    • v
    Leibniz has your back:

    "Leibniz' Law", the formulation often referred to as "the indiscernibility of identicals" says:

    if a = b, then for all F, Fa iff Fb

    The contrapositive of this (if this thing has a property that thing doesn't have, then they're not the same thing) is your suggested test.

    There's a correlative, more controversial, thesis known as "the identity of indiscernibles" that says:

    if for all F, (Fa iff Fb), then a = b

    The applicability of all this crystalline logic to the goopy semantic web, though, is a little more tangled ...
    • ^
    • v
    I guess that if in your definition, you guarantee that truth is something variable in time and context, and that we can NOT know about all assertions.

    In newtonian physics, time is an absolute concept.
    In general relativity, time is a variable concept.
    • ^
    • v
    Hi Phil, long time no see.

    I've been struggling for a while to find a way to start explaining (even to myself) just what it is about very much of the "semantic web" chat about the place that I find so desperately incoherent. Nothing personal, but this looks as good a place to start as any ;).

    Let's take a look into that fine philosophy of language text Alice Through the Looking-glass

    [the White Knight said] The name of the song is called "HADDOCKS' EYES."'

    `Oh, that's the name of the song, is it?' Alice said, trying to feel interested.

    `No, you don't understand,' the Knight said, looking a little vexed. `That's what the name is CALLED. The name really IS "THE AGED AGED MAN."'

    `Then I ought to have said "That's what the SONG is called"?' Alice corrected herself.

    `No, you oughtn't: that's quite another thing! The SONG is called "WAYS AND MEANS": but that's only what it's CALLED, you know!'

    `Well, what IS the song, then?' said Alice, who was by this time completely bewildered.

    `I was coming to that,' the Knight said. `The song really IS "A-SITTING ON A GATE": and the tune's my own invention.'
    Do I need to add anything?

    I will anyway.

    How can the meaning of an identifier by anything other than the entitity it identifies? And how can you, in general, know what that is?

    It's suggested here and there that an RFC 2821 style email address might make a good URI for a person. And others have pointed out that this is preposterous. I agree with the second group.

    Quickly now, does the URI mailto:info@bogotek.co.el identify a person, or not? How do you know?

    By the way, the .el TLD is used for hosts in the People's Republic of Elbonia, where "Fo" is a common family name. And BogoTek's IT director has a fetish for short email addresses. And there's a guy in sales called Iolanthe Norbert somthing-or-other.

    RFC 2821 itself even has something to say about this:
    2.3.10 Mailbox and Address

    As used in this specification, an "address" is a character string that identifies a user to whom mail will be sent or a location into which mail will be deposited. The term "mailbox" refers to that depository. The two terms are typically used interchangeably unless the distinction between the location in which mail is placed (the mailbox) and a reference to it (the address) is important. An address normally consists of user and domain specifications.

    The standard mailbox naming convention is defined to be "local-part@domain": contemporary usage permits a much broader set of applications than simple "user names". Consequently, and due to a long history of problems when intermediate hosts have attempted to optimize transport by modifying them, the local-part MUST be interpreted and assigned semantics only by the host specified in the domain part of the address.
    Emphasis mine.

    I couldn't find any help about whether or not WordPress interprets markup inside comments (and I've a nasty feeling it's not going to let me come back and edit this if not) so apologies in advance if required.
    • ^
    • v
    If I've understood you correctly, you're basically saying that nobody can really know the true 'meaning' of an identifier (i.e. what it identifies) apart from the owner/creator of that identifier?

    I suspect it's worse than that - even the owner/creator modifies and refines their interpretation of the identifier in subtle ways wrt time and context of communication. You've got a whole bunch of dimensions in which the 'meaning' can vary, it's a wonder that anybody can know what anything means with a high degree of precision.

    In reality we all have our own in-head models of what different words and identifiers mean under different circumstances, and for meaningful communication to take place these need to intersect appropriately between the parties within the context of the exchange. (and there probably needs to be a mechanism for negotiation of meaning, just as in human communication).

    That's why I'm not convinced that trying to use URIs to identify abstract things is going to fly on a global scale. I think URIs imply a level of precision that doesn't exist in the messy real world (the implication being that you can use the URI in isolation to uniquely identify something without requiring the context of the communication).

    They do however work nicely for uniquely identifying web resources because the meaning is grounded in the lookup mechanism that all parties share.
close Reblog this comment
Powered by Disqus · Learn more
blog comments powered by Disqus