I guess I'm also late to this discussion. But I always assumed:
1. The ALTO costs are end-to-end. Always.
2. An ALTO server is expected to give the costs between *every* pair of
PIDs. It can omit a cost only if it cannot determine that cost at all.
3. You cannot infer a topology from the 'holes' in the cost map.
4. If it were possible to calculate the missing costs by using SPF (or
whatever) on the other costs, then the ALTO server should do that! The
ALTO server shouldn't push that task onto the clients.
- Bill Roome
>On Mon, Jan 30, 2012 at 9:03 AM, Ben Niven-Jenkins
><[email protected]> wrote:
>>Colleagues,
>>
>>In the current specification of ALTO, are costs always End to End?
>>
>>What I mean by that is when looking at ALTO cost maps is it possible to
>>safely assume that of there is a cost between PIDX & PID Y and a cost
>>between PIDY & PIDZ then the cost between PIDX & PIDZ can be calculated
>>as cost(PIDX,PIDY)+cost(PIDY,PIDZ)? [If this assumption does hold, it is
>>obviously not applicable to ordinal cost types].
>>
>>I suspect the answer is no, but I wanted to check what the definitive
>>answer is.
>>
>>
>>For example if a cost map contains:
>>
>>? "map" : {
>>? ? "PID1": { "PID2": 1 },
>>? ? "PID2": { "PID1": 1, "PID3": 2 },
>>? ? "PID3": { "PID2": 2 }
>>
>>Can one assume that the cost between PID1 & PID3 is 3 (PID1->PID2 +
>>PID2->PID3)?
>>
>>How about if the cost map contains:
>>
>>? "map" : {
>>? ? "PID1": { "PID2": 1, "PID3": 3 },
>>? ? "PID2": { "PID1": 1, "PID3": 2 },
>>? ? "PID3": { "PID2": 2, "PID1": 3 }
>>
>>Can one assume PID2 is on a path between PID1 & PID3?
>>
>>Thanks
>>Ben
>>
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>
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