Re: [Rdfapi-php-interest] Re: explicit individual statement reification

[Richard C. <ri...@cy...>]

Hi Saf,

Sorry for the long delay.

On 16 Sep 2005, at 13:10, Saf Hulou wrote:
> The last point - rap won't let me create a reified statement from a
> uri is precisely my problem.

Ah, I see. It's a RAP limitation.

> It seems that I will have to create the blank node and create a  label
> for the blank node, as you suggest. This is a bit wierd though.
> How do I pass a blank node id or a model to a reify function?

When you pass a blank node, then that blank node will simply be used  
as the subject of the four reification statements. To create a blank  
node, do "$blank = new BlankNode($model)".

What happens when you pass a model is this: RAP creates a new blank  
node, which becomes the representation of the reified statement. The  
model is needed only because of the way RAP creates blank nodes. RAP  
uses the model to make sure that the blank node is unique (within  
that model).

Don't you have a model anyway where your statements are stored? You  
just can use that model as the argument to $statement->reify. You  
don't have to create a new model.

> Isn't it a bit meaningless to create a blank node or model before I've
> reified the statement? Are they simply  placeholders?

As I said, you don't have to create the blank node yourself. The  
reify method can create it for you. However, you have to pass in some  
model because RAP needs one to create unique blank nodes. Don't pass  
a new model every time, but re-use the model you're working with anyway.

> I think I'm misunderstanding something here....

Sorry about that. RAP's reification support is a bit strange and  
doesn't seem to be used very much.

I think what you probably want to do is this:

    $new_blank_node = $model->reify_statement($statement)

This would create a new blank node and it would add the four  
reification statements to $model.

In RAP you have to do this to get the same effect:

    $new_blank_node = new BlankNode($model)
    $reification_quad = $statement->reify($new_blank_node)
    $model->addModel($reification_quad)

(But this doesn't work currently because of a bug, I'll send a  
separate mail about that.)

Hope that helps.
Richard



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