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Comments

vlorbik

it seems to me that for discussions of RST, one should use only _binary_ relations: if our relation is called ~, for example, the usual "infix" notation x~y means that the ordered pair (x,y) is an element of the set of ordered pairs called ~ (recall that a relation, by definition,
_is_ a set of ordered pairs).

the definitions you've pointed at (using the world's most famous _equivalence_ relation) seem to depend on the infix notation.

how are we to speak of reflexivitiy, for example, if we consider a trinary relation? i don't get it.

Polymath

hmmm...

I'm not sure I follow your objection. All of the relations in my list are intended to be taken as binary relations.

X has-a-class-with Y, where X and Y are students, means that (X,Y) is in the set of ordered pairs that includes all pairs of students that have a class together.

I don't think any of my relations are trinary. Perhaps I need to make some of the definitions more clear?

vlorbik

my fault entirely; sorry.
i careless took your lines

congruent (R, S, T)
complementary-to (S)

as refering to a trinary
and unary relation respectively
(didn't notice that you'd
*clearly stated* that you were
providing "answers"; in the
unlikely event that anybody
else is still so confused,
R, S, and T have their "obvious"
meanings (reflexive, ...).

like that old lady used to say,
"never mind ..." ...

Xerxes1729

Not-equal-to is symmetric, but it's not reflexive.

Polymath

ah yes, thanks xerxes...the post now reflects the correction.

Mrs. Scarpa

Do you by any chance have the lesson plan you used to teach this lesson? I am a beginning teacher interview for a position and I have to teach this for my demo lesson. Any help would be much appreciated.

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