Re: [rdf4j-dev] Substring implementation difference between jena, rdf4j

[Jerven Tjalling Bolleman <Jerven.Bolleman@sib.swiss>]

Hi Jeen, Håvard,

I think the bug is on our side.
I opened a pull request with what I think matches the xpath spec.
Added all the examples as test cases.

Hope, I did it ok. Still forgetting to commit with -s :(

Pulling this in is not urgent for me. I found out that
this allows a "wrong" query to return a "right" result.
Fixing my own queries is good enough for me, but I think
we should be exact in regards to matching specs.

We should have a preprint out with the why of the queries
by next week.

Regards,
Jerven

On 2019-03-24 21:33, Håvard Ottestad wrote:
> Relevant from the xml spec:
>
> The expression fn:substring("12345", 0, 3) returns "12". _(Characters
> at positions greater than or equal to 0 and less than 3 are selected.
> Since the first position is 1, these are the characters at positions 1
> and 2.)_
>
> So it’s perfectly legal to do substring(“a”, -9999, 9999), which
> returns “a”.
>
> Håvard
>
> > On 24 Mar 2019, at 21:25, Jeen Broekstra <jeen.broekstra@xxxxxxxxx>
> > wrote:
> >
> > Good find Jerven.
> >
> > You might also file a bug with Jena for the 0, 1 edge case. I only
> > glanced at the spec but it seems to me that in that case the answer
> > should still be "A", not the empty string.
> >
> > Cheers,
> >
> > Jeen
> >
> > On Mon, 25 Mar. 2019, 05:25 Jerven Tjalling Bolleman,
> > <Jerven.Bolleman@sib.swiss> wrote:
> >
> > > Hi James, All,
> > >
> > > I didn't see an example with startingLoc less than 1.
> > >
> > > However, one document down in the xpath-functions one there is
> > > clarity.
> > > https://www.w3.org/TR/xpath-functions/#func-substring
> > > And I should have looked at that first.
> > >
> > > I think this means edge case non conformance bugs in rdf4j and
> > > virtuoso.
> > >
> > > I will propose a fix for it in rdf4j and file a bug for it for
> > > virtuoso.
> > >
> > > i.e. SUBSTR("ABC", 0, 2)
> > > should return "A" because only for position 1
> > > does fn:round(0) <= 1 and 1 < fn:round(0) + fn:round(2) hold
> > >
> > > Regards,
> > > Jerven
> > >
> > > On 2019-03-24 17:38, james anderson wrote:
> > > > > On 2019-03-24, at 15:34:55, Jerven Tjalling Bolleman
> > > > > <jerven.bolleman@sib.swiss> wrote:
> > > > >
> > > > > Hi All,
> > > > >
> > > > > Cross posting as this seems to be a question of spec
> > > implementation
> > > > > and I am not sure what the correct answer is supposed to be.
> > > >
> > > > look at the examples in the document which you referenced.
> > > >
> > > > best regards, from berlin,
> > > > ---
> > > > james anderson | james@xxxxxxxxx | http://dydra.com [1]
> > >
> > > --
> > > Jerven Tjalling Bolleman
> > > SIB | Swiss Institute of Bioinformatics
> > > CMU - 1, rue Michel Servet - 1211 Geneva 4
> > > t: +41 22 379 58 85 - f: +41 22 379 58 58
> > > Jerven.Bolleman@sib.swiss - http://www.sib.swiss [2]
> > >
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>
> Links:
> ------
> [1] http://dydra.com/
> [2] http://www.sib.swiss/

--
Jerven Tjalling Bolleman
SIB | Swiss Institute of Bioinformatics
CMU - 1, rue Michel Servet - 1211 Geneva 4
t: +41 22 379 58 85 - f: +41 22 379 58 58
Jerven.Bolleman@sib.swiss - http://www.sib.swiss