example.sparql

PREFIX foaf: <http://xmlns.com/foaf/0.1/> 
PREFIX doap: <http://usefulinc.com/ns/doap#> 

SELECT ?project ?maintainer WHERE {
       ?p doap:name ?project .
       ?p doap:maintainer ?m .
       ?m foaf:name ?maintainer .
}

jena-output.txt

$ ~/Projects/rdf/jena/apache-jena-2.12.1/bin/sparql --data http://ldf-server-python.herokuapp.com/ --query example.sparql
--------------------------------
| project      | maintainer    |
================================
| "ldf-server" | "Eric Moritz" |
--------------------------------

output.txt

$ time ./node_modules/ldf-client/bin/ldf-client http://ldf-server-python.herokuapp.com/ example.sparql -l debug
[Thu Nov 20 2014 01:23:19 GMT-0500 (EST)] INFO HttpClient Retrieving http://ldf-server-python.herokuapp.com/
[[Thu Nov 20 2014 01:23:19 GMT-0500 (EST)] INFO HttpClient Retrieving http://ldf-server-python.herokuapp.com/?p=http%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2Fname
[Thu Nov 20 2014 01:23:19 GMT-0500 (EST)] INFO HttpClient Retrieving http://ldf-server-python.herokuapp.com/?p=http%3A%2F%2Fusefulinc.com%2Fns%2Fdoap%23name
[Thu Nov 20 2014 01:23:19 GMT-0500 (EST)] INFO HttpClient Retrieving http://ldf-server-python.herokuapp.com/?p=http%3A%2F%2Fusefulinc.com%2Fns%2Fdoap%23maintainer

real	0m0.382s
user	0m0.240s
sys	0m0.041s

Hi @ericmoritz,

Thanks for starting this!

The reason the LDF client does not give a result, is that the triple pattern fragments are not yet complete.
Triple Pattern Fragments consist of data, metadata, and controls.

As we can see from the debug log above, the controls are working: the client is able to retrieve other fragments from the start fragment. However, the metadata—which is necessary for the client to execute queries efficiently—is missing:

$ curl 'http://ldf-server-python.herokuapp.com/?p=http%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2Fname'
@prefix ns1: <http://www.w3.org/ns/hydra/core#> .
@prefix ns2: <http://xmlns.com/foaf/0.1/> .
@prefix ns3: <http://rdfs.org/ns/void#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xml: <http://www.w3.org/XML/1998/namespace> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<http://eric.themoritzfamily.com/> ns2:name "Eric Moritz" .

<http://ldf-server-python.herokuapp.com/#dataset> a ns3:Dataset,
        ns1:Collection ;
    ns3:subset <http://ldf-server-python.herokuapp.com/?p=http%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2Fname> ;
    ns1:search [ ns1:mapping [ ns1:property rdf:predicate ;
                    ns1:variable "p" ],
                [ ns1:property rdf:object ;
                    ns1:variable "o" ],
                [ ns1:property rdf:subject ;
                    ns1:variable "s" ] ;
            ns1:template "http://ldf-server-python.herokuapp.com/{?s,p,o}" ] .

We need a triple such as the following:

<http://ldf-server-python.herokuapp.com/?p=http%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2Fname> void:triples 1.

Note that this count does not have to be exact; an approximation is sufficient.