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    1:- module(prophier, []).    2:- use_module(library(semweb/rdf_db)).    3:- use_module(library(assoc)).    4:- use_module(library(http/http_dispatch)).    5:- use_module(library(http/html_write)).    6
    7:- use_module(components(label)).	% Get rdf_link//1
    8:- use_module(cliopatria(hooks)).	% Declaration to extend the menu

Vizualize the RDF property hierarchy

This program demonstrates simple data processing and vizualization. In order to process the request, we

compute the hierarchy as a Prolog datastructure (using property_tree/1). This allows for reuse, for example emitting the same datastructure as JSON, so we can do the rendering in Javscript at the client side.
emit the tree as a nested ul structure

Finally, we can add it to the ClioPatria menu by adding a clause for cliopatria:menu_item/2.

To be done: - Add style to make it look pretty. */

   28% Make our predicate respond to /prophier
   29
   30:- http_handler(root(prophier), property_hierarchy, []).   31
   32% add our application to the Places  menu.   300  is the location in the
   33% menu (check cp_menu:menu_item/2 for the initial   menu). places is the
   34% popup and property_hierarchy is the identifier  of our handlers, which
   35% defaults to the predicate name. See http_handler/3 for details.
   36
   37cliopatria:menu_item(300=places/property_hierarchy, 'Predicate tree').

property_hierarchy(+Request): HTTP Handler that emits the RDF property hierarchy as a nested ul tree where the properties are links to the ClioPatria local view.

   45property_hierarchy(_Request) :-
   46	property_tree(Tree),
   47	reply_html_page(cliopatria(default),
   48			title('Property hierarchy'),
   49			[ h1('RDF Property hierarchy'),
   50			  \emit_tree(Tree)
   51			]).
   52
   53
   54emit_tree([]) --> !.
   55emit_tree(List) -->
   56	html(ul(\emit_children(List))).
   57
   58emit_children([]) --> [].
   59emit_children([node(P,Children)|T]) -->
   60	html(li([ \rdf_link(P)		% Create link to local view
   61		| \emit_tree(Children)
   62		])),
   63	emit_children(T).

property_tree(-List) is det

Compute the entire property hierarchy for the RDF database. Most of the complication is due to the fact that we need to take care of possible loops in the property hierarchy. For this purpose, we use library(assoc) to maintain an binary tree of predicates we already expanded.

Arguments:

List - is a list of terms node(Predicate, Children)

   76property_tree(List) :-
   77	empty_assoc(Done0),
   78	findall(node(P, _), p_root(P), List),
   79	children(List, Done0, _Done).
   80
   81p_root(P) :-
   82	rdf_current_predicate(P),
   83	\+ rdf_has(P, rdfs:subPropertyOf, _).
   84
   85children([], Done, Done).
   86children([node(P, Children)|T], Done0, Done) :-
   87	(   get_assoc(P, Done0, _)	% Already in the tree
   88	->  Done = Done0
   89	;   put_assoc(P, Done0, true, Done1),
   90	    findall(node(P2, _), rdf_has(P2, rdfs:subPropertyOf, P), Children),
   91	    children(T, Done1, Done2),
   92	    children(Children, Done2, Done)
   93	)