Re: Separation of configuration and control - good or bad?

[Juergen Schoenwaelder <schoenw@ibr.cs.tu-bs.de>]

>>>>> Phil Shafer writes:

Phil> The biggest cons to using xpath are:

Phil> - Lack of schema-ability: Since xpath strings are just strings,
Phil> you can't validate a request against a schema to know that your
Phil> request is valid.

Not sure I understand this. If a filter expression does not match,
then the result is empty. What is wrong with this? It seems to work
in other places.

Phil> - Distinct syntax: While it's certainly possible to convert from
Phil> a configuration hierarchy into the xpath expression that
Phil> represents it, it's not trivial. Converting the other way (xpath
Phil> -> element) is even more difficult, though it would likely be
Phil> rarely required.

It seems to work in other places, so why not here? I know research
prototypes that use xpath in xml to snmp gateways. Sure, you can say
that this if fine but will never work on real boxes. This brings us
back to a previous thread which I do not want to repeat.

Phil> - Assymetric syntax: Using a different syntax for rpc input
Phil> parameters than rpc output parameters seems unnatural and will
Phil> make applications that what to perform simple data transforms
Phil> more difficult.

Filter expressions are something different than configuration or
operational state data. There are several other network management
protocols where filters or queries are not the same as the data they
manipulate.

/js

-- 
Juergen Schoenwaelder		International University Bremen
Phone: +49 421 200 3587		P.O. Box 750 561, 28725 Bremen, Germany
Fax:   +49 421 200 3103		<http://www.iu-bremen.de/>

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