Moving from xpath 1.0 to a newer version of xpath impacts certain
implementations in non-trivial ways. Note that the WG charter says:
The NETMOD Working Group will produce a maintenance release of the
core YANG specification called YANG 1.1, that is a revision of RFC
6020. The changes to RFC 6020 are restricted in the following ways:
- All compliant YANG 1.0 modules must be accepted as compliant YANG
1.1 modules.
- All known ambiguities of YANG 1.0 and all reported defects and
errata will be addressed.
- YANG 1.1 is not adding fundamentally new data modeling concepts to
the language.
- The changes of the specification will be kept to the minimum
necessary to achieve the previously stated goals.
Moving to a more powerful version of xpath is out of scope for YANG
1.1. Note that we are wrapping things up, the deadline for submitting
feature requests has long passed.
/js
On Tue, Feb 02, 2016 at 12:32:47AM +0000, fengchong (C) wrote:
> Hi all,
> I notice draft-ietf-netmod-rfc6020bis-09 still uses xpath1.0 as a notation
> for checking node references or dependencies.
> I don’t know why we don’t use xpath3.0 or xpath2.0? xpath3.0 is more powerful
> than xpath1.0.
> For example, xpath3.0 introduced conditional expression. It’s very useful for
> must statement.
>
> If we have a schema tree like this:
> List l {
> Key a;
> Leaf a {…}
> Leaf b {…}
> Leaf c {…}
> Leaf d {…}
> }
>
> If a= 5 and b=10 and c >20, then d must be less than 30 and greater than 15.
> If use xpath1.0, the MUST statement should be:
> Must “a != 5
> or b != 10
> or c <=20
> or (a =5 and b = 10 and c>20 and d >15 and d < 30)”
> if use xpath3.0:
> must “if (a =5 and b = 10 and c>20)
> then d>15 and d<30
> else true()”
>
> if we feel xpath3.0 is too complicated, we can specify a small set of xpath
> grammar for YANG.
>
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