I figured that the builtin isNext(?seq, ?X, ?Y) I'm creating is called only
if X = Y. weird...
In my test, my rdf:seq has 3 members. If I try to see what is inside the
Environment:
System.out.println("Context env: " + context.getEnv().toString());
I obtain in the console:
-5824a9a0:135858b0e5e:-7ffe rdf:_1 http://example.com/resA
http://example.com/resA
-5824a9a0:135858b0e5e:-7ffe rdf:_2 http://example.com/resB
http://example.com/resB
-5824a9a0:135858b0e5e:-7ffe rdf:_3 http://example.com/resC
http://example.com/resC
where I guess -5824a9a0:135858b0e5e:-7ffe is my rdf:seq.
Is it a normal behaviour ?
Benjamin
On Thu, Feb 16, 2012 at 9:05 AM, Dave Reynolds <[email protected]>wrote:
> On 15/02/12 17:29, benjamin jailly wrote:
>
>> Thank you for your reply Dave.
>>
>> based on your advice, I'm trying to create a builtin in the form:
>> isNext(?seq, ?X, ?Y) that returns true if Y is the element right after X
>> in the rdf:seq seq.
>>
>>
>> So I extended the BaseBuiltin class and wrote my functions like this :
>>
>> @Override
>> public boolean bodyCall(Node[] args, int length, RuleContext context)
>> {
>> checkArgs(length, context);
>> Node seq = getArg(0, args, context);
>> Node n1 = getArg(1, args, context);
>> Node n2 = getArg(2, args, context);
>> return isNext(seq, n1, n2, context);
>> }
>> /**
>> * Return true if element2 is right after element1 in the seq
>> */
>> protected static boolean isNext(Node node, Node element1, Node
>> element2, RuleContext context ) {
>> Model m = ModelFactory.**createDefaultModel();
>> RDFNode seq = m.asRDFNode(node);
>> RDFNode elt1 = m.asRDFNode(element1);
>> RDFNode elt2 = m.asRDFNode(element2);
>>
>
> Creating a new model for each call to the builtin is a little expensive,
> better to just work at the Node level.
>
> if (seq == null || seq.equals(RDF.Nodes.nil) ||
>> !seq.canAs(Seq.class) ) {
>> m.close();
>> return false;
>> } else {
>> // get indexes of elt1 and elt2
>> int i1 = seq.as <http://seq.as>(Seq.class).**indexOf(elt1);
>> int i2 = seq.as <http://seq.as>(Seq.class).**indexOf(elt2);
>>
>> System.out.println("res: " + i1 + "," + i2);
>>
>
> That won't work because the new empty model in which those RDFNodes sits
> has no statements in it to support the indexOf operations.
>
> It would be better to do the test by extracting the sequence number from
> the URI of the Nodes.
>
> [Note that one of the many complications with Seq is that the sequence
> numbers need not be contiguous. That doesn't affect your builtin and might
> not affect your rules if you have control over the data but if you are
> expecting to process data "from the wild" then it will be something to bear
> in mind.]
>
> Dave
>
