A3 Q3 Solution

[zaid....@gmail.com]

Hi,

I have a question about the solution to A3 Q3. In particular, I'm
concerned that solution does not address the precise wording of the
question.

My concern is that the question asks about active replication *in
general* and the solution's interpretation of the term "in general"
seems to be inconsistent with the usual interpretation of the term.

The solution states:

"Consider read operations that operate on nonmodifed data or
commutative write operations (where a op b = b op a)."

This is a *specific* concept that does NOT apply to active replication
*in general*. Therefore, *in general* active replicatation DOES
require that all operations be carried out in the same order.

Also note that the actual question is stated in the second sentence of
the question text and contains the "this" modifier that references the
previous sentence, so the "in general" term is absolutely relevant to
the question.

Can the course staff please comment on this. The question is either
badly worded or I missed something?

Thanks.

[zaid....@gmail.com]

Also just another comment on that... the question that has been
answered in the solution is:

"Is there a case where all operations do not have to be carried out in
the same order at each replica? Explain."

Rather than the actual (paraphrased) question:

"Is this ordering [for all operations to be carried out in the same
order at each replica] always necessary [for active replication in
general]?"

[Hao Chen]

Hi, the "in general" part is what you've told, which means in the most of
the cases, the ordering of operations is important. The question is asking
if this ordering is absolutely always necessary, which indicates that you
should think of some (specific) cases where this ordering doesn't matter.

Hao

<zaid....@gmail.com> wrote in message
news:1144885182.3...@u72g2000cwu.googlegroups.com...

[Hao Chen]

I admit that the phrasing of this question could be improved, so you don't
treat it a simple yes/no question. However, we are trying to avoid these
situations, but we cann't guarantee that this won't happen at all, simply
because of the different thinking. Sometimes, you probably should interpret
the logic just a little bit. But anyway, if you are uncertain about
anything, please ask.

Hao

<zaid....@gmail.com> wrote in message
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