Anyone know how we submit Worlds?

Some of the questions can be answered (sounds more convenient) using World files. Now as far as I'm aware, myUnisa will only accept a single file in a certain number of formats (not including Open Office, unfortunately). Am I wrong?

Or can you embed the World file as an object in a pdf file?

I suppose a better place to ask this question would be in the social cafe, where there are inhabitants who've been here and done this, but that would break the forum rules. Pity.

Reply to self: I've made enquiries, and this is the Windows answer:

"The best way to submit Worlds using myUnisa is to use:

Shift Print Screen
Then paste to paint
Cut from paint into Word doc
To avoid distortion of your work, convert the Word doc to pdf.
Otherwise you just have to cut one of the worlds at the back of your tutorial letter 101 and do it manually, it is acceptable."

Report back: This (obviously) works. (Duh, eddy). I've saved as a PNG because they're meant to make better use of memory, and the default BMP files aren't portable. Due to incompetence on my part, I then have to use my SneakerNet system to get it onto the working file on the other machine.

You can also just lay out the world as written in the tutorial letter (with blocks) and then write the code for the object in the relevant blocks.

I submitted by putting a table in my word document and then writing in the correct cell LD or was it DL (for large dodec). Also, when you have to do it in the exam you have to know how to fill it in like this.

That's a good point. What, did you copy and paste from the pdf? Or did you scan the forms? -- ER adjust -- OK, I think what you're saying is you made a blocks world out of a table on the word processor?

I'd like to do that, but unfortunately I'm helleva lazy, so I probably never will.

Yup, just made a table in the word document. It's not a lot of work and when it's done once you just copy paste it everywhere and edit the cells.

OK, but the former lecturer for the course did send me an easier alternative. Put together a World in Tarski, screenshot, bang, done. (And then maybe practice on paper worlds in one's free time - as you say, in the exams they'll expect us to be competent at manually completing these, so it's a good tip to get familiar with that format as soon as one can).

OK, now there's at least one fellow scholar of note over here, I suppose I'd better go and dig around in LPL to see if there are interesting logical matters we can discuss profoundly here.

Lol! I did the course last year. Hopefully I'll still remember most of it when the time comes for discussions!

Good luck for the course - hope it goes well

Thanks. Are you going on further with logic, or have you taken it as far as you need?

So far, all the things I thought were interesting are already on the other threads. I've discovered that Truth Tables really do know nothing, for instance. They know that "everything is possible" - ie. they think "nothing is impossible". Haven't gotten much further than that. Hmm...

I must go and look back in that book. There was one thing the Grade Grinder kept on telling me I had completely wrong, each time I submitted it, and I think I just made a note and moved on. Maybe you'll have some insight on whatever it was I was getting stuck on - assuming later chapters haven't cleared it up for me already.

I've basically pushed through to the end of the work for assignment 1 and am now idling somewhere near the beginning of Chapter 5 (while I catch up like mad with other things). Page 130. (I've fetched the book). Maybe tonight I must go in search of that open question, put it into a proper bug report form, and give it a thread.

Oh, and good luck with whatever courses you're doing, too.

I've taken the logic courses as far as I plan to. I'm not really keen on taking the third level module as I think there are others I would find more useful. The best courses I've taken so far were actually the COS201 and COS301 series on Theory of Computation. I highly recommend those! And they were great to take in conjunction with logic. This year I'm taking the C++ one (COS211) and the assembler one (COS221) (I think it's assembler - haven't opened the books yet!) and COS226 (networking) and INF320.

What other courses are you taking this year?

And go ahead and post that question when you find it - I'm interested to see what I remember!

OK, that's approximately what I'm thinking of taking next year if I survive this one. I've started reading a book on assembly several times, but don't ever seem to get beyond chapter 1 before something crops up.

This year I'm running at about my personal limit (beyond, actually, it occasionally feels). MAT103, APM114, PHY105, MAT211 (trying to sneak in as much maths as I can), then COS214, COS261, INF er Intro to Business Systems, and then HCI I in S2, INF206, INF207. My INFs are lagging behind my COSs so I thought I'd better push to catch up there.

Let me go and hunt for that question:... Got it surprisingly quickly. Here goes:

According to Tarski's World, the following is unevaluable (I hope that's not just my guess as to what Tarski said):

A || (B && !

Now I would've thought it should evaluate to A. ie. A || {nonsense} --> A

My note says "NB. [ Cube(b) || !Cube(b) ] is unevaluable. It 'poisons' any || it's connected to."

What do you make of this?

Further note: This came out of the section on Tautological Consequence, so this could be another of those properties of Truth Tables being very mechanical (like computers, I suppose, so perhaps this is an abstraction of a reality we have to deal with when interacting with these sometimes idiotic machines).

If you take it that B means B is a cube. Then in the statement B && !B you are effectively saying, B is a cube and B is not a cube. It is not logically possible for B to be a cube and not a cube at the same time. So it's impossible to put that on a World diagram. How would you indicate it is an is not a cube? Because that part is already unevaluable, there is nothing more that || A can add.

It's important to remember that Tarski's World is only looking at a sentance and seeing if it could be placed on a World.

Then if you look at B || !B, I don't think that this one is unevaluable - but I'm not sure on this one. If you have on a world that B is a cube OR B is not a cube, it is still evaluable. For example, if we had a previous statement that said B is a square. Then we could still evaluate the sentence of B || !B because !B is true.

Let me write that out rather
A = Square( B ); //so B is a square
C = Cube( B ) || ! Cube( B ) // we have been told that B is a square so B can't be a cube.

So what C becomes is C = false || true, thus C = true.

Then for this world I would just have put a Square named B on the board. Come to think of it, I'm sure there were examples in the textbook of B || !B.

Hope that helps

rezrovs Wrote:

> It's important to remember that Tarski's World is
> only looking at a sentance and seeing if it could
> be placed on a World.
>

Oh bugger! I haven't quite figured this "quote" thing. I see it works more or less like a traditional newsgroup posting now. Have deleted whatever it was I said <think, think> .. Ah! I whined about the smileys. It's a very mildly upsetting when a parenthetic expression like '(B && !' gets smilified into B && {no grin with sunglasses}.

I then noticed that I shifted the goalposts in mid-posting and ended with B || !B, but said never mind, you made something interesting out of that. Tidied up, && proved logically that it's evaluable, IOW.

And yes the reply was very helpful. The quote above was particularly helpful. It's at that point that the candle in the cavern behind the eyes was ignited, and glowed a little. Yes, B && !B is = {nonsense} ... But How would one show this in Tarski's World? You can't. So it's unevaluable. In Tarski's World. Yes, that helps a lot.

In the wider world of logic outside of the constraints of Tarski's World, however, it still seems to me (I suppose by ^Elim) that {Something Logically Possible} || {Logical garbage} should evaluate to {Something Logically Possible}?

Socrates is mortal or Socrates is a glonkfarter and Socrates is also not a glonkfarter.
Well we know Socrates can't both be and not be a glonkfarter ... so ... zrrrt spark spark flash flame .... it's unevaluable, isn't it? It's not true; it's not false; it's just jibberish. I'll change my mind here. One gets stuck on the absurdity if one's serious about evaluating everything proposed....

Is Socrates mortal? Maybe. We first have to wait and see what to make of his both being and not being...

But could a bee, be said to be, when half that bee must half not be - due to some ... injury ... Maybe Monty Python were onto something?

Anyway, you're dead right about the B || !B
And about the fact that one must remember what universe of discourse we're using. (Is that what Tarski's World is? A universe of discourse? Or am I getting set theory and logic mixed up here?)

No, I'm wrong.

A || [B && !B] must evaluate to A outside of a constrained world. The compound statement [B && !B] is evaluable outside Tarski's World, and the world of Tautologies; it's False. It's a logical fallacy, false of itself, without regard to what B may assert.

So then if [B && !B] is False, then the entire compound proposition evaluates to A is True.

However, this cannot be demonstrated using Tarksi's World.

If I've got that right, then I understand quite a bit more about logic now than I did 24 hours ago.

That is what I understand - ( B && !B ) is always false anywhere. The thing is that in Tarski's World you can't represent this.

The idea is that Tarski's World can only be used to show things that are TW-possible. And from there you get TT-Possible but I don't remember much of how the different types of possibility build on top of one another.

OK, I've been through this recently, so let me test my short term memory. Basically it moves from the most restrictive through the general to the particular (I haven't worked out a single sorting method for this).

{centre} ...{TT-possible} .... {Logically possible} ..... {TW-possible} ... Outside are things possible in other specific worlds. For instance !Bee(eric) || HalfBee(eric) is a possibility in Python's World, but you can't represent it in TW. ... I've thought I've grasped the full significance of that a few times in the last few minutes, but have done you the courtesy of deleting my insights into the relationship between the "outer space" to logical possibility.

The outer rings include the inner, so if something's TT-possible it's a subset of those things that are logically possible - which makes sense. I still don't have a strong grasp of how logical possibilities are a subset of TW-possibilities. Caught a glimpse of it the other day, but it seems to have slipped my mind.

Oh hang on, if a thing's logically possible, it must be TW-possible? Yes. Logically possible. Not impossible ....

You can represent anything logically possible in TW. That doesn't mean you can represent logical falsehoods. How does that sound? It only works in a "positive sense". The opposite case doesn't follow automatically.

The other thing is that the subset relationship doesn't imply equivalence (certainly the way the rings are drawn, it means quite the opposite). So Logical possibilities are not always TT possibilities. Some things are logically possible and not TT possible.

Back again. Went looking for the diagram showing logical possibilities in the text book. Some of the finest cursing you could ever hope to hear later, I realised that the only such diagram in the earlier part of the book is one showing logical necessities in the various worlds.

TT-necessities are always --> also logical necessities --> and these are always TW necessities.
TT-necessities < --- Logical necessities, which are not always <--- TT necessities are not always

De Morgan's laws hold from the centre to the very outside. If it applies in a truth table, then it applies in all cases.

Cube(a) || Tet(a) || Dodec(b) is just any old "OR" as far as a truth table is concerned.
is just any old "OR" as far as logic at large is concerned.
is a necessary truth of TW.

All right, so how does that relate to logical possibility?

First question would be "What is logical possibility?", I suppose: "It's possible for this proposition to be true; it need not necessarily be true; however, neither is it necessarily false".

That suggests that "logically possible" is just a less convoluted way of saying "Not logically impossible - that is to say, not necessarily false".

B && !B is necessarily false. It's not a logical possibility. Allowing B && !B into logic would destroy logic, I suspect.

OK, I'm stuck. I can't see how to fit this into the wheel diagram. I'll go watch Prof Lewin performing his physics circus act then, and hope somehow it all stews away in the background and later just pops out, answered.

Don't you find that often the best way to solve a problem is to leave it alone? It's almost as if what you need to do is inflict questions on your mind. Get it all irritated with unanswered questions. Then you bail out forever, but the brain is now annoyed, so keeps grinding away, stealing processing time from the Tom and Jerry cartoons you've decided would be "less boring", stealing processing time from your dreamlands, churning away churning away, nagging at the questions that nag. Then hey presto! Wake up in the morning, and the first thing you think of is the answer to something you abandoned as impossible (if in humble mode) or "boring" (if in vain mode). Most people I've talked to say this happens to them.

Imagine fMRIing a problem-beset brain till it spits out its answer. (Or injecting it with iodine or some radioactive isotope). That'd be interesting. Maybe that's the thing to target careerwise. Go into software support for neuroscientists. (This is all avoidance of that nagging question somewhere up there, which is just too boring for me to waste too many precious hours on).

Thanks rezrovs for the suggestion of drawing the table in Word.