15. The method of claim 14, wherein each of said data elements in said subtrees is classified into a type category and wherein the method further comprises the step of specifying permitted connections between data elements, said permitted connections defining the types of data elements that may be connected and the type of relationships permitted between types of data elements.
14. A method of inserting a list of subtrees comprising a plurality of simply connected data elements constituting nodes into a tree in relation to a selected target node having a parent node, said list of subtrees being maintained in a storage means of a data processing system, said method being performed by said data processing system in response to selections and directions of an operator through operator interaction means, said method comprising the steps of: (a) specifying a relationship between said list of subtrees and said target node; (b) if said relationship is specified as "left" or "right", connecting each subtree in the list of subtrees to said parent such that said subtree is connected to said parent before said target node, if left, or after said target node, if right; (c) if said relationship is specified as "around": (1) disconnecting said target node from said parent node; (2) connecting each subtree in said list of subtrees to said parent node as subsidiary data elements thereof; and (3) connecting said disconnected target node to said list of subtrees; (d) if said relationship is specified as "within": (1) disconnecting the subsidiary data elements of said target node; (2) connecting each subtree in said list of subtrees to said target node as subsidiary data elements thereof; and (3) connecting said disconnected subsidiary data elements to each subtree in said list of subtrees.