/**
 * A general interface for folder data objects. 
 * Folders are important for structured datasources. They will also contain all the links
 * from the folder to its containing children (using the appropriate relating property) in
 * its getMetadata() RDF Map. So you can get the identifiers of children either using hte
 * getChildren() method or via getMetadata() where all the children are also listed.
 * Listing the relations between folders and their children is very useful for large
 * search databases, that can make use of the semantic structure.
 * 
 */
public interface DataObjectFolder {

    
        /**
         * Gets the data object's parent, if any.
         * 
         * @return the parent DataObject, or null when this DataObject has no parent.
         */
        public DataObject getParent();
    
        /**
         * Gets the data object's children, if any. This may be null to indicate that there
         * are no children. 
         * @return an Iterator over DataObject objects
         */
        public Iterator getChildren();

    
        /**
         * Get the source-specific metadata and data.
         * The used keys and values and implementation-dependent. 
         * For java1.4 compability reasons, the map is untyped.
         * It is already titled RDFMap to reflect our ideas regarding RDF
         * 
         * @return The scheme-specific metadata.
         */
        public RDFMap getMetadata();

}