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    1/*  Part of ClioPatria SeRQL and SPARQL server
    3    Author:        Jan Wielemaker
    4    E-mail:
    5    WWW: 
    6    Copyright (C): 2010-2018, University of Amsterdam,
    7		              VU University Amsterdam,
    8                              CWI, Amsterdam
   10    This program is free software; you can redistribute it and/or
   11    modify it under the terms of the GNU General Public License
   12    as published by the Free Software Foundation; either version 2
   13    of the License, or (at your option) any later version.
   15    This program is distributed in the hope that it will be useful,
   16    but WITHOUT ANY WARRANTY; without even the implied warranty of
   18    GNU General Public License for more details.
   20    You should have received a copy of the GNU General Public
   21    License along with this library; if not, write to the Free Software
   22    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   24    As a special exception, if you link this library with other files,
   25    compiled with a Free Software compiler, to produce an executable, this
   26    library does not by itself cause the resulting executable to be covered
   27    by the GNU General Public License. This exception does not however
   28    invalidate any other reasons why the executable file might be covered by
   29    the GNU General Public License.
   32:- module(cliopatria, []).

ClioPatria hooks

This module declares the hooks an application may define to extend or modify some of ClioPatria's behaviour. Hooks are multifile defined predicates that -typically- have no default definition. Code using the hook typically first calls the hook. If the hook succeeds the task is considered done. Otherwise some default action is performed. For example, a property myprefix:componentName can be added as a property that provides a label using this code:

:- use_module(cliopatria(hooks)).


The example below adds an item to Help popup of ClioPatria:

:- use_module(cliopatria(hooks)).
:- use_module(library(http/http_dispatch)).

cliopatria:menu_item(help/about, 'About').

:- http_handler(root(about), about, []).

about(Request) :-
    <generate the about page>


   65:- multifile
   66	menu_item/2,
   67	menu_label/2,
   68	menu_popup_order/2,
   70	rdf_label:label_property/1,
   71	bnode_label//1,			% +Resource
   72	display_link//2,		% +RDFObject, +Options
   73	resource_link/2,		% +URI, -URL
   75	list_resource//2,		% +URI, +Options
   77	user_preference_db/2,		% ?Property, ?Value
   78	user_preference_default/2,	% ?Property, ?Value
   80	page_body//1,			% +Body
   81	page_body//2,			% +Style, +Body
   82	server_address//0,
   83	logo//0,
   85	predicate_order/2,		% +P, -Order
   86	context_graph/2,		% +R, -RDF
   87	context_graph/3,		% +R, -RDF, +Options
   88	context_predicate/2,		% +R, -Pred
   89        node_label/4,                   % +R, +Lang, +MaxLen, -Label
   90	node_shape/3,			% +R, -Shape, +Options
   91	bag_shape/3.			% +Members, -Shape, +Options
   94		 /*******************************
   95		 *	     THE MENU		*
   96		 *******************************/
 menu_item(?Item, ?Label)
This hook adds an item to the ClioPatria menu. Item is a term of the form [rank=]popup/item, where popup denotes the name of the popup menu and item is a (new) item to be added to the popup. The item is the handler-identifier of the HTTP handler that implements the item (see http_handler/3). Label is the label displayed. rank defines the position inside the popup. The built-in items are numbered 100,200,...

For example, if we want to add a new item to the Repository menu after Load from library that crawls LOD data, we can use the following code:

:- use_module(cliopatria(hooks)).
:- use_module(library(http/http_dispatch)).

:- handler(cliopatria('crawl_lod_form'), crawl_lod_form, []).

cliopatria:menu_item(400=repository/crawl_lod_form, 'Crawl LOD').

crawl_lod_form(Request) :-
See also
- The menu_label/2 and menu_popup_order/2 hooks provide further control over the menu.
- cp_menu:menu_item/2 implements the default menu.
 menu_label(+Id, -Label)
This hook allows for dynamic or redefined (e.g., multilingual) labels. It is called both for popup-identifiers and item-identifiers.
 menu_popup_order(+Id, -Location:integer)
This hook controls the order of the popup-item of ClioPatria's menu.
  140		 /*******************************
  141		 *		LABELS		*
  142		 *******************************/
True if the value of Property can be used to (non-uniquely) describe an object to the user. This hook provides additional facts to label_property/1.
HTML-write DCG rule that produces an HTML description for the given RDF blank node. See bnode_label//1.
HTML-write DCG rule that produces an HTML description for the given RDFObject (a resource or literal) with an appropriate link. This predicate is called by the RDF browser to present RDF triples.
 resource_link(+URI, -URL)//
URL is the link created by rdf_link//1 for URI. The default opens the ClioPatria `local view'.
See also
- cpa_browse:list_resource/1 is the handler addressed by the default link.
- cp_label:resource_link/2 calls the hook.
  172		 /*******************************
  173		 *	    LOCAL VIEW		*
  174		 *******************************/
 list_resource(+URI, +Options)//
This hook is called by cpa_browse:list_resource//2, which display the `local view' page for a resource. This can be used to create a different page for describing a resource and still using overall infrastructure such as rdf_link//1.
  184		 /*******************************
  186		 *******************************/
 user_preference_db(?Property:atom, ?Value:rdf_object) is nondet
Query properties for the current user/session. This mechanism allows code to access information about the user/session without committing to a particular implementation. The predicate and values are compatible with RDF to allow implementing the user database in RDF, typically using the OpenID as subject.
 user_preference_default(?Property:atom, ?Value:rdf_object) is nondet
Provides defaults for the user_preference/2.
See also
- user_preference_db/2
  203		 /*******************************
  204		 *	       SKINS		*
  205		 *******************************/
 page_body(+Body)// is semidet
 page_body(+Style, +Body)// is semidet
Emit the body of the page. This can be used to provide a different skin for ClioPatria. The Style argument is passed from reply_html_page/3. The file skin(cliopatria) defines the overall skin and first calls cliopatria:page_body//2, if this fails cliopatria:page_body//1 and if this fails too it uses the default page.
HTML-write DCG rule that writes the address of the server. If you want to maintain its normal position in the page layout, this should create an element of class address using the class cliopatria.
Logo placed left of the menu-bar. Must be an object that has float:left style.
  230		 /*******************************
  231		 *	    RDF BROWSING	*
  232		 *******************************/
 predicate_order(+Pred, -Order) is semidet
Define the order in which predicates appear in the local view. The Order is an integer. The system ordering is defined by cpa_browse:p_order/2. Predicates that are not explicitly ordered are placed at the end of the table an ordered alphabetically.

Predicates that have order `0' are deleted from the table.

 context_graph(+R, -RDF, +Options) is semidet
- Use context_graph/3.
 context_graph(+R, -RDF, +Options) is semidet
This hook redefines the context graph shown by the RDF browser for the resource R. RDF is a list of rdf(S,P,O) triples that describe the context. Typically only object-triples are used, although that is not a requirement.
See also
- This predicate hooks cpa_browse:context_graph/3. Please visit the soure to learn about available building blocks.
 context_predicate(+Subject, -Predicate) is nondet
True when rdf(Subject, Predicate, _) must be included in the context graph for Subject.
 node_label(+URI, +Lang, +MaxLen, -Label) is semidet
Compute a label for URI in the given language, truncating the label to MaxLen characters.
 node_shape(+URI, -Shape, +Options) is semidet
Compute the desired shape for a GraphViz node representing URI.
URI- is the resource for which to determine the shape
Shape- is a list Name(Value) for parameters given to GraphViz.
Options- provides additional guidance. Currently it may provide start(StartURI) to indicate the graph is a context node for the resource StartURI.
See also
 node_shape(+Bag, -Shape, +Options) is semidet
Compute the desired properties for a table used to display a bag of resources. Shape options include:
Only show the first Max members of the bag. Default is 5.
Basic shape
Style options
Truncate labels that have more then Chars characters.
Bag- is a list of member resources