/**
* Returns a new Model that is the set-union of the model with another model.
* Duplicate statements are removed. If you want to allow duplicates, use addModel() which is much faster.
*
* The result of taking the set-union of two or more RDF graphs (i.e. sets of triples)
* is another graph, which we will call the merge of the graphs.
* Each of the original graphs is a subgraph of the merged graph. Notice that when forming
* a merged graph, two occurrences of a given uriref or literal as nodes in two different
* graphs become a single node in the union graph (since by definition they are the same
* uriref or literal) but blank nodes are not 'merged' in this way; and arcs are of course
* never merged. In particular, this means that every blank node in a merged graph can be
* identified as coming from one particular graph in the original set of graphs.
*
* Notice that one does not, in general, obtain the merge of a set of graphs by concatenating
* their corresponding N-triples documents and constructing the graph described by the merged
* document, since if some of the documents use the same node identifiers, the merged document
* will describe a graph in which some of the blank nodes have been 'accidentally' merged.
* To merge Ntriples documents it is necessary to check if the same nodeID is used in two or
* more documents, and to replace it with a distinct nodeID in each of them, before merging the
* documents. (Not implemented yet !!!!!!!!!!!)
*
* @param object Model $model
* @return object MemModel
* @access public
* @throws phpErrpr
*
*/
function &unite(&$model)
{
if (is_a($model, 'ResModel')) {
return $this->model->unite($model->getModel());
}
return $this->model->unite($model);
}
