Re: subtree filtering: content match nodes

[Martin Bjorklund <mbj@tail-f.com>]

Andy Bierman <ietf@andybierman.com> wrote:
> Hi,
> 
> I just read sec. 6.2.5 again in RFC 4741, and found yet another 'concern'
> with subtree filtering.
> 
> The text in the 2nd sentence explicitly states  wrt/ to
> a content match node:  "it represents an exact-match filter".
> 
> I cannot find any text anywhere that mentions canonical data formats,
> or schema data type conversion.  It is extremely likely that an
> agent implementation will need to convert between a numeric data type
> and a string representation of that data type to support this feature.
> 
> For interoperability, we should have a precise meaning of 'exact match'.
> 
> Does 'exact match' mean that the agent MUST NOT convert the
> filter value to any schema-defined data type (i.e., convert number
> to canonical and/or internal format, or adjust string whitespace or
> convert character entities)?
> 
> Instead, the agent must compare a string representation of the internal
> value to the exact filter string value.
> 
> Or is the agent allowed to convert the raw filter string to an internal
> (schema defined) data type before comparing it to the value from the
> target config?
> 
> IMO, the post-conversion compare is more user-friendly.

I fully agree.

But we also have this text in 6.2.5:

   o  Leading and trailing whitespace characters are ignored, but any
      whitespace characters within a block of text characters are not
      ignored or modified.

I think that's a mistake.  If I have a xs:string in my db which has
the value " hello ", I cannot match it with a subtree filter.  IMO, it
would have been better to not try to do whitespace adjustments, but
instead follow the normal rules imposed by the datatype.

But I guess the reason for all this is:

   The agent does not need to utilize any data-model specific
   semantics during processing, allowing for simple and centralized
   implementation strategies.


... and now instead for example it's not clear if the float '1.0'
"exactly matches" '1.00' or '1.



/martin

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