Resolve a URI.
@param href The relative URI of the collection. This corresponds to theargument supplied to the collection() function. If the collection() function was called with no arguments (to get the "default collection") this argument will be null.
@param base The base URI that should be used. This is the base URI of thestatic context in which the call to collection() was made, typically the URI of the stylesheet or query module
@param context The dynamic execution context
@return an Iterator over the documents in the collection. The items returnedby this iterator must be instances either of xs:anyURI, or of node() (specifically, {@link org.pdf4j.saxon.om.NodeInfo}.). If xs:anyURI values are returned, the corresponding document will be retrieved as if by a call to the doc() function: this means that the system first checks to see if the document is already loaded, and if not, calls the registered URIResolver to dereference the URI. This is the recommended approach to ensure that the resulting collection is stable: however, it has the consequence that the documents will by default remain in memory for the duration of the query or transformation.
If the URI is not recognized, the method may either return an empty iterator, in which case no error is reported, or it may throw an exception, in which case the query or transformation fails. Returning null has the same effect as returning an empty iterator.