Partial orders

• Jan 18th 2009, 01:16 PM
cj's mom
Partial orders
State whether the following relations is a partial order

isAncestorOf

isSisterOf

{(2,1),(1,3)(2,3)}
• Jan 18th 2009, 01:43 PM
Plato
Quote:

Originally Posted by cj's mom
State whether the following relations is a partial order

isAncestorOf

isSisterOf

{(2,1),(1,3)(2,3)}

Why don't you tell us what you think the answers are?
• Jan 18th 2009, 01:51 PM
cj's mom
I thought it was

yes

no

yes

but I wanted to check it out.
• Jan 18th 2009, 02:06 PM
Plato
Quote:

Originally Posted by cj's mom
I thought it was

yes

no

yes

but I wanted to check it out.

Be sure you check each as to being reflexive, antisymmetric and transitive.
• Jan 19th 2009, 05:27 AM
cj's mom
Partial order
I looked at the relations
is Ancestor of
A is an ancestor of A = reflexive
if A is an ancestor of B then B is not an ancestor of A
if A is an ancestor of B and B is an ancestor of C then A is an ancestor of C.

The one I am stuck on is the antisymmetric.

Looking back I think the first two are yes and the last one is no
• Jan 19th 2009, 08:32 AM
Plato
Quote:

Originally Posted by cj's mom
I looked at the relations
is Ancestor of
A is an ancestor of A = reflexive

Do you really think that you are an ancestor of yourself?
Maybe we have different definitions of ancestor.
• Jan 19th 2009, 08:46 AM
cj's mom
partial
okay I give up
• Jan 19th 2009, 08:57 AM
Plato
Quote:

Originally Posted by cj's mom
okay I give up

No, don't give up.
This is either a badly worded question or you did not take time to type up the exact question.
Usually a well written question would have given the domain of the relation.
Moreover, it is not good form to use such term as ancestor without defining it.
• Jan 19th 2009, 10:58 AM
cj's mom
partial
That is the way it is written with no other information.