Re: Semantics and Belief contexts - was: PaceDuplicateIdsEntryOrigin posted
Part of the reason I went into the detailed explanation I did, is because not everyone here may be familiar with mathematical logic. What I was explaining is a heavy condensation of what I learned in my BA in philosophy. I am not plucking these thoughts out of a hat. So let me apply these a little more directly to your proposal. I very much agree with the spirit of what you are saying. But I think that the danger is that by looking at the problem the way you are, we may end up confusing things a lot more than we are clarifying them. On 25 May 2005, at 21:06, Antone Roundy wrote: == Rationale == * The accepted language for allowing duplicate IDs in a feed document speaks only multiple atom:entry elements with the same atom:id describing the same entry if they exist in the same document--of course, we intend for them to describe the same entry whether they're simultaneously in the feed document or not If we put this in terms of ontology, what we want is to state simply that an ID refers to one and only one entry. There is not much to add by the way, other than that the ID is a URI, since the whole role of URIs is to identify one and only one thing. * The accepted language does not speak of the origin feed of the entries. Ideally, an atom:id should be univerally unique to one entry resource, and we rightly require publishers to mint them with that goal. However, in reality, malicious or undereducted publishers might duplicate the IDs of others. Therefore, it is proposed to modify the specification to state that the atom:entry elements describe the same entry (resource) if they originate in the same feed. When you say 'ideally', I say ontologically. Let us imagine that instead of creating an ontology for a atom entry, we were creating one for a gun. We could say that guns have a number of properties, one of them being that they are physical objects. Physical objects can only be at one place at a time. So a gun can only be at one place at a time. Now you can see how it won't help the definition of a gun if someone were to introduce the following reasoning. When a policeman asks someone where they put the gun, some people are honest and tell them where, but many people (the most interesting ones) will lie to them. The policeman has to report the facts as he sees and hears them. He may hear two conflicting reports on where the gun is. Are guns therefore weird objects that have a position relative to the person who speaks about them? This is confusing semantics and the way people speak about the world. It is confusing our concepts about the world, and the context in which sentences containing those concepts about the world appear. * Aggregators wishing to protect against DOS attacks are not unlikely to perform some sort of safety checks to detect malicious atom:id duplication, regardless of whether the specification authorizes them to or not. The policeman is not unlikely to do a lot of safety checks to find out where the gun is. He may for example scan the person who told him he has not gun anyway, just to make sure. On 25 May 2005, at 22:57, Antone Roundy wrote: On Wednesday, May 25, 2005, at 02:26 PM, Henry Story wrote: Since the referents of Superman and Clark Kent are the same, what is true of the one, is true of the other. When speaking directly about the world, we can replace any occurrence of Superman with Clark Kent, and still say something true. Clark Kent is the secret identity of Superman. - Superman is the secret identity of Superman. Whether they're perfectly interchangeable or not depends on whether the name is referring to the object or some a facet of the object. The second sentence actually works if the first Superman refers to the persona, and the second to the person. But getting back to Atom... There are a lot of corner cases. I was trying to give an overview of a complicated field. I was restricting myself to sentences where words clearly identify objects. If you use Superman to refer to a persona then we are speaking about something else. Other cases are Superman is so called because he is strong. Well known, but it does not undermine the distinction I was making. [snip] So to prevent a DOS attack, best is to have aggregator feeds such as: feed !-- aggregator feed -- feed src=http://true.org; idtag://true.org,2005/feed1/id entry titleEnter your credit card number here/title ... /entry /feed feed src=http://false.org; idtag://true.org,2005/feed1/id entry titleEnter your credit card number here/title ... /entry /feed /feed Here all the aggregator feed is claiming is that he has seen entries inside other feeds. ... It will be up to the consumer of such aggregated feeds to decide which to trust. From the end user's point of view, it's not much
Semantics and Belief contexts - was: PaceDuplicateIdsEntryOrigin posted
On 25 May 2005, at 21:06, Antone Roundy wrote: * The accepted language does not speak of the origin feed of the entries. Ideally, an atom:id should be univerally unique to one entry resource, and we rightly require publishers to mint them with that goal. However, in reality, malicious or undereducted publishers might duplicate the IDs of others. Therefore, it is proposed to modify the specification to state that the atom:entry elements describe the same entry (resource) if they originate in the same feed. * Aggregators wishing to protect against DOS attacks are not unlikely to perform some sort of safety checks to detect malicious atom:id duplication, regardless of whether the specification authorizes them to or not. I understand your motivation, but I think it is misguided. I only recently understood why myself [1]. Let me explain a little how I come to this conclusion. An easy way to understand semantics is to think of it as about the objects out there. Take the sentences: (a) Superman can fly (b) Superman is Clark Kent we can immediately deduce truly that (c) Clark Kent can fly. Since the referents of Superman and Clark Kent are the same, what is true of the one, is true of the other. When speaking directly about the world, we can replace any occurrence of Superman with Clark Kent, and still say something true. When we are speaking about what others believe, this is no longer true. Lois Lane may believe (a) without believing (c). She may think Superman is a hero, but not think that Clark Kent is one. There is in logic therefore a fundamental distinction between sentences used in a direct semantic way, and sentences used in this indirect way, when the sentence is in a belief context. This distinction is so fundamental that there is a well known mental illness that goes with people who are not able to make this distinction: autism. Autistic children have great difficulty understanding the difference between what is and how people perceive things to be. In RDF this distinction shows up when moving from triples to 4- tuples. RDF/XML is a language that works best in the Semantic realm. With triples we can describe objects and their relationships. If we want speak about consistent ways of seeing the world we need to group statements with formulae as is done in N3[2] and TriX for example. This then allows us to name consistent sets of statements. It also allows one to simultaneously refer to sets that are inconsistent. I can for example consistently hold the following: Lois lane believes that Superman is different from Clark Kent Clark Kent believes that he is Superman. without contradiction. So how does this relate to Atom? Well we need to be clear that semantically a entryId and a feedId point to one thing and one thing only. But this does not mean that there can not be erroneous, false, corrupted,... feeds out there. Aggregators wishing to protect against DOS attacks should simply do what we humans do in such circumstances, namely quote what others are saying and not assert the things others are saying. This is why the proposal by Roy Fielding to allow feeds inside of feeds was probably the best way to do things (I just came to this conclusion yesterday, before this I had no idea what he was going on about). So to prevent a DOS attack, best is to have aggregator feeds such as: feed !-- aggregator feed -- feed src=http://true.org; idtag://true.org,2005/feed1/id entry titleEnter your credit card number here/title ... /entry /feed feed src=http://false.org; idtag://true.org,2005/feed1/id entry titleEnter your credit card number here/title ... /entry /feed /feed Here all the aggregator feed is claiming is that he has seen entries inside other feeds. He never need claim to agree with any of their content. And so the content of the first internal feed and the second internal feed can be contradictory. They can for example have the same id with the same updated timestamp and with different content. It will be up to the consumer of such aggregated feeds to decide which to trust. The good thing about this way of doing things is that one can define a first level feed in a simple semantic vocabulary, without needing to create all kinds of exceptional clauses all over the place. When dealing with feeds inside a feed one can then simply mention that this indirection is equivalent to the belief context indirection. Statements can be contradictory across such internal feeds. Taking this into account should help make the spec a lot cleaner, easier to write and easier to understand. The problems are fundamental, so they cannot be swept under the carpet. They will keep popping up. Henry Story [1] http://www.imc.org/atom-syntax/mail-archive/msg15608.html [2]
Re: Semantics and Belief contexts - was: PaceDuplicateIdsEntryOrigin posted
On Wednesday, May 25, 2005, at 02:26 PM, Henry Story wrote: Since the referents of Superman and Clark Kent are the same, what is true of the one, is true of the other. When speaking directly about the world, we can replace any occurrence of Superman with Clark Kent, and still say something true. Clark Kent is the secret identity of Superman. - Superman is the secret identity of Superman. Whether they're perfectly interchangeable or not depends on whether the name is referring to the object or some a facet of the object. The second sentence actually works if the first Superman refers to the persona, and the second to the person. But getting back to Atom... Autistic children have great difficulty understanding the difference between what is and how people perceive things to be. They sure don't have a monopoly on this! Really getting back to Atom!... So to prevent a DOS attack, best is to have aggregator feeds such as: feed !-- aggregator feed -- feed src=http://true.org; idtag://true.org,2005/feed1/id entry titleEnter your credit card number here/title ... /entry /feed feed src=http://false.org; idtag://true.org,2005/feed1/id entry titleEnter your credit card number here/title ... /entry /feed /feed Here all the aggregator feed is claiming is that he has seen entries inside other feeds. ... It will be up to the consumer of such aggregated feeds to decide which to trust. From the end user's point of view, it's not much different. Somebody still has to make the decision, and the end user doesn't want to be the one doing it--they want the super aggregator or their feed reader or somebody else to do it for them. The feed reader should be doing it anyway, since they won't be getting all of their data through a super aggregator. But the super aggregator is likely to want to do it too, both to reduce how much data they forward to their clients, and because many feed readers aren't going to do it very well, so handling part of the job for them will improve the end user's experience. I'm not a fan of feeds of feeds (though I have proposed and still like a one-level embedding of feeds in a different top-level element). Plus, I think it's inconceivable that the WG would make this drastic a change at this point. Let's focus on doing what's actually possible, given the WG schedule and temperment, to mitigate this problem.
