Re: [regext] Poll messages with unhandled namespaces (was Re: I-D Action: draft-ietf-regext-change-poll-07.txt)

[Thomas Corte <[e-mail]>]

Hello,

On 7/16/18 16:46, Martin Casanova wrote:

> ... The precondition of this approach is, that we actually can ask all
> registrars to prepare their clients to at least tolerate new poll
> messages and to update their business logic in order to process the
> newly given information properly if they wish to do so. I think this
> should be the case and no problem for most registrars already.

There is a problem with this approach if the EPP client (like ours) uses
an XML parser that validates against the configured XML schema
definitions. Such a client will inevitably choke on any unknown
namespaces, since reading the message will fail on the parsing layer
already (without the business logic even getting a chance to look at the
message).
Note by the way that using a schema-validating EPP client is actually
beneficial since it allows the code consuming data from the registry's
responses to simply assume that certain data must be present and/or
follow a certain format, without the need for additional checks; i.e.
it's not just a case of being particularly pedantic.

To "tolerate new poll messages" in such a scenario would require
disabling the schema validation altogether, which would reintroduce the
need for addition checks in code that were previously handled by the
parsing layer.

I'm therefore much in favor of the previously discussed solution
involving the <extValue> element. It's not perfect, but it allows
schema-validating EPP clients to read and acknowledge unknown poll
messages which would otherwise block the queue.

Best regards,

Thomas

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