Re: subtree filtering: content match nodes

[Li Yan <liyan_77@huawei.com>]

Hi,
There is no such text (like sec. 6.2.5) to describe how the XPath filter matches the leaf node content in RFC 4741.
Does XPath filtering have the same issue?

Yan

----- Original Message ----- 
From: "Andy Bierman" <ietf@andybierman.com>
To: "Martin Bjorklund" <mbj@tail-f.com>
Cc: <netconf@ops.ietf.org>
Sent: Monday, May 21, 2007 10:33 PM
Subject: Re: subtree filtering: content match nodes


Martin Bjorklund wrote:
> 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.

Yes.
And the following filter cannot be given  -- &sp;hello&sp; -- because
character entities are not replaced first.  You can never search for
the '<' and '>' characters either.

> 
> 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.
> 
> 

The string "1.0" does not match "1" or "+1" or "+1.0".

> 
> /martin

Andy



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