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    1/*  Part of ClioPatria SeRQL and SPARQL server
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2010-2018, University of Amsterdam,
    7                              VU University Amsterdam,
    8                              CWI, Amsterdam
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- 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)).

rdf_label:label_property(myprefix:componentName).

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>

   70:- multifile
   71    menu_item/2,
   72    menu_label/2,
   73    menu_popup_order/2,
   74
   75    rdf_label:label_property/1,
   76    bnode_label//1,                 % +Resource
   77    display_link//2,                % +RDFObject, +Options
   78    resource_link/2,                % +URI, -URL
   79
   80    list_resource//2,               % +URI, +Options
   81
   82    user_preference_db/2,           % ?Property, ?Value
   83    user_preference_default/2,      % ?Property, ?Value
   84
   85    page_body//1,                   % +Body
   86    page_body//2,                   % +Style, +Body
   87    server_address//0,
   88    logo//0,
   89
   90    predicate_order/2,              % +P, -Order
   91    context_graph/2,                % +R, -RDF
   92    context_graph/3,                % +R, -RDF, +Options
   93    context_predicate/2,            % +R, -Pred
   94    node_label/4,                   % +R, +Lang, +MaxLen, -Label
   95    node_shape/3,                   % +R, -Shape, +Options
   96    bag_shape/3,                    % +Members, -Shape, +Options
   97    edge_shape/3.                   % +P, -Shape, +Options
   98
   99
  100                 /*******************************
  101                 *           THE MENU           *
  102                 *******************************/

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.

  146                 /*******************************
  147                 *              LABELS          *
  148                 *******************************/

rdf_label:label_property(?Property): 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.

bnode_label(+Resource)//: HTML-write DCG rule that produces an HTML description for the given RDF blank node. See bnode_label//1.

display_link(+RDFObject)//: 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.

  178                 /*******************************
  179                 *          LOCAL VIEW          *
  180                 *******************************/

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.

  190                 /*******************************
  191                 *   USER/SESSION PREFERENCES   *
  192                 *******************************/

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

  209                 /*******************************
  210                 *             SKINS            *
  211                 *******************************/

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.

server_address//: 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//: Logo placed left of the menu-bar. Must be an object that has float:left style.

  236                 /*******************************
  237                 *          RDF BROWSING        *
  238                 *******************************/

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

deprecated: - 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.

Arguments:

`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.

bag_shape(+Bag, -Shape, +Options) is semidet

Compute the desired properties for a table used to display a bag of resources. Shape options include:

max(Max): Only show the first Max members of the bag. Default is 5.
shape(Shape): Basic shape
style(Style): Style options
max_label_length(Chars): Truncate labels that have more then Chars characters.

Arguments:

Bag

- is a list of member resources

edge_shape(+Triple, -Shape, +Options) is semidet

Compute the desired attributes for a GraphViz edge representing the predicate Triple.

Arguments:

`Triple`	- is the triple 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.