Re: [alto] Discussion II: Unifying cost-mode and cost-type to a single type

[Wendy Roome <[e-mail]>]

I'd like to propose a radical change to "cost mode". But first, I make the
following assertion:

"Ordinal" mode exists to allow ALTO servers to hide the details of their
network. For a client, "ordinal" mode has no advantage over "numerical"
mode; clients will never explicitly request an "ordinal" mode cost.
"Ordinal" mode benefits servers, not clients.

If you accept that, then I claim there's no reason for an ALTO server to
provide both "ordinal" and "numerical" values for the same cost type. If
the server wants to hide the network details, it will only provide an
"ordinal" cost. If the server doesn't mind exposing the details, it will
provide a "numerical" cost.

So I suggest the logical conclusion is that we drop "mode" as we've been
using it. Instead, a cost type has a binary-valued "linear" attribute
("true" => "numerical", "false" => "ordinal"). The ALTO server decides
whether a cost type is linear, and declares it in the resource directory.
The client lives with that decision; the client cannot chose to get an
ordinal cost.

In other words, I think we've over-engineered the concept of "cost mode",
and we should simply it.

	- Wendy Roome