| [hyades-dev] XML-based command data |
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At last week's face-to-face we discussed the possibility of switching the command data format for proposed HCE protocol from a binary, byte-stream-based format to an XML-based format. Rather than make any hasty changes to the current proposal, I wanted to air this explicitly on this mailing list and give everyone (particularly those who weren’t present last week) a chance to voice whatever concerns they might have.
I believe there was some consensus that this was a good idea so long as we kept it to a simple description of the data (perhaps leveraging some existing standard).
However, at some point on Thursday Harm raised the possibility that there are scenarios in which it is necessary to send large amounts of binary data on the command channel. I would have serious reservations about using XML some of the time but occasionally switching to binary, but if someone familiar with this case can propose something reasonable, I'm willing to listen.
We agreed, I think, on Friday that this would apply only to the command header and command data, not to the message envelope (which is specific to the transport layer being used).
One concern I have is that if we use XML to describe command data, I want to be sure we have very clearly defined rules for how and when additional fields can be added, including the expected behavior if a command with the new data is sent to an object that isn't expecting it (i.e. what are the implications of ignoring the data) and the expected behavior if a command without the data is sent to an object that is looking for it (i.e. what is the default).
I don't want the interfaces to become amorphous.
Other comments?
Should we switch to XML-based command data? |