On Fri, Feb 21, 2025 at 1:01 PM Andy Seaborne <a...@apache.org> wrote:
>
>
>
> On 12/02/2025 21:03, Martynas Jusevičius wrote:
> > Hi Andy,
> >
> > I understand the differences of how they are implemented.
> >
> > I think what I'm missing is a sort of overview of when those different
> > approaches should be used, and also examples of when they produce
> > semantically different queries.
>
> string template substitution can alter or break queries.
>
> Replace ?X in {?s :p ?X} with the '"text" . FILTER (?s != :hideMe )'
I understand that simple string replacement is not safe.
But can there be differences in query semantics after a value was
injected using ParameterizedSparqlString vs. Substitute?
>
> https://xkcd.com/327/
>
> Andy
>
> >
> >
> > Martynas
> >
> > On Thu, Feb 6, 2025 at 5:59 PM Andy Seaborne <a...@apache.org> wrote:
> >>
> >>
> >>
> >> On 06/02/2025 03:24, Nicholas Car wrote:
> >>> You could try running that with RDFlib and see what it does….
> >>>
> >>> How is substitute() different to just string template substitution? Is it
> >>> just a convenience function so substitution can be done on a Jena SPARQL
> >>> object (perhaps algebra) rather than a string?
> >>
> >>
> >> It does not work on a string - when working with Query objects (e.g.
> >> service enhancer), manipulate is on Query objects.
> >> It does does not have injection attacks.
> >>
> >> There some places where you can't replace a variable by a value
> >>
> >> BIND(123 AS ?X)
> >>
> >> for example. QueryTransforOps checks.
> >>
> >> Substitute.substitue is a collect of algebra to algebra changes - some
> >> of which are used in execution.
> >>
> >>>
> >>> Is that your goal for an RDFLib equivalent?
> >>
> >> See also ParameterizedSparqlString in Jena which is injection-safe.
> >> That's closer to string replacement.
> >>
> >> Under the general concept of "substitute" there are different uses cases
> >> on different objects.
> >>
> >> Andy
> >>
> >>> SPARQL string to/from SPARQL grammar object is handles in RDFLib fine so
> >>> I guess as I think the code says, an RDFLib substitute() could work on
> >>> either or both.
> >>>
> >>> Nick
> >>>
> >>> On Thu, Feb 6, 2025 at 10:05 am, Martynas Jusevičius
> >>> <[marty...@atomgraph.com](mailto:On Thu, Feb 6, 2025 at 10:05 am,
> >>> Martynas Jusevičius <<a href=)> wrote:
> >>>
> >>>> OK I simply fed Jena's source to ChatGPT and asked it to produce an
> >>>> RDFLIb version :)
> >>>> No idea if it's correct but I'll find out I guess.
> >>>>
> >>>> from rdflib import Variable, BNode, Literal
> >>>> from rdflib.plugins.sparql.algebra import BGP, Filter, Join, LeftJoin,
> >>>> Union, Graph, Extend, Minus, OrderBy, Project
> >>>>
> >>>> def substitute(algebra, binding):
> >>>> if isinstance(algebra, BGP):
> >>>> new_triples = []
> >>>> for s, p, o in algebra.triples:
> >>>> s = binding.get(s, s)
> >>>> p = binding.get(p, p)
> >>>> o = binding.get(o, o)
> >>>> new_triples.append((s, p, o))
> >>>> return BGP(new_triples)
> >>>> elif isinstance(algebra, Filter):
> >>>> new_p = substitute(algebra.p, binding)
> >>>> new_expr = algebra.expr
> >>>> for var, val in binding.items():
> >>>> new_expr = new_expr.substitute(var, val)
> >>>> return Filter(new_expr, new_p)
> >>>> elif isinstance(algebra, Join):
> >>>> return Join(substitute(algebra.p1, binding),
> >>>> substitute(algebra.p2, binding))
> >>>> elif isinstance(algebra, LeftJoin):
> >>>> return LeftJoin(substitute(algebra.p1, binding),
> >>>> substitute(algebra.p2, binding), algebra.expr)
> >>>> elif isinstance(algebra, Union):
> >>>> return Union(substitute(algebra.p1, binding),
> >>>> substitute(algebra.p2, binding))
> >>>> elif isinstance(algebra, Graph):
> >>>> return Graph(algebra.term, substitute(algebra.p, binding))
> >>>> elif isinstance(algebra, Extend):
> >>>> new_p = substitute(algebra.p, binding)
> >>>> new_expr = algebra.expr
> >>>> for var, val in binding.items():
> >>>> new_expr = new_expr.substitute(var, val)
> >>>> return Extend(new_p, new_expr, algebra.var)
> >>>> elif isinstance(algebra, Minus):
> >>>> return Minus(substitute(algebra.p1, binding),
> >>>> substitute(algebra.p2, binding))
> >>>> elif isinstance(algebra, OrderBy):
> >>>> return OrderBy(substitute(algebra.p, binding), algebra.expr)
> >>>> elif isinstance(algebra, Project):
> >>>> return Project(substitute(algebra.p, binding), algebra.PV)
> >>>> else:
> >>>> return algebra
> >>>>
> >>>> On Thu, Feb 6, 2025 at 12:54 AM Martynas Jusevičius
> >>>> <marty...@atomgraph.com> wrote:
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> I was looking to implement something like substitute() using RDFLib.
> >>>>>
> >>>>> I checked the note:
> >>>>> https://afs.github.io/substitute.htm
> >>>>> But I couldn't find a clear example.
> >>>>>
> >>>>> For example, how would this query string (the template)
> >>>>>
> >>>>> PREFIX dbo: <http://dbpedia.org/ontology/>
> >>>>> CONSTRUCT
> >>>>> WHERE { ?city dbo:populationTotal ?population }
> >>>>>
> >>>>> would look like after substituting (?city,
> >>>>> <http://dbpedia.org/resource/Copenhagen>)?
> >>>>>
> >>>>>
> >>>>> Martynas
> >>
>
