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— causalconnector [2014/09/16 14:26] (current)
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 +===== The <causalConnector> Element =====
 +==== Definition and Usage ====
 +
 +The [[causalconnector|<causalConnector>]] element represents a causal relation that may be
 +used for creating relationships ([[link|<link>]] elements) in NCL documents.  In
 +a causal relation, a condition must be satisfied in order to trigger an
 +action.
 +
 +A [[causalconnector|<causalConnector>]] specifies a relation independently of
 +relationships, that is, it does not specify which nodes (represented by
 +[[media|<media>]], [[context|<context>]], [[body|<body>]], and [[switch|<switch>]] elements) will
 +interact through the relation.  A [[link|<link>]] element, in its turn,
 +represents a relationship of the type defined by its referred connector,
 +interconnecting different nodes.  Links representing the same type of
 +relation, but interconnecting different nodes, may reuse the same connector,
 +reusing all its previous specification.
 +
 +A [[causalconnector|<causalConnector>]] defines, through its child elements, a set of
 +interface points, called roles.  A [[link|<link>]] element refers to a
 +[[causalconnector|<causalConnector>]] and defines a set of binds ([[bind|<bind>]] child
 +elements of the [[link|<link>]] element), which associate each link endpoint
 +(node interface) to a role of the referred connector.
 +
 +Relations in NCL are based on events.  An NCL event is an occurrence in time
 +that may be instantaneous or have a measurable duration.  Each event defines
 +a state machine that is maintained by the NCL player (see Figure 1).
 +Moreover, every event has an associated attribute, named
 +//occurrences//, which counts how many times the event transits from
 +occurring to sleeping state during a document presentation.  Events of
 +presentation and attribution types have also an attribute named
 +//repetitions//, which counts how many times the event shall be
 +automatically restarted (transited from sleeping to occurring states) by the
 +NCL player.  This attribute may contain the "indefinite" value, leading to
 +an endless loop of the event occurrences until some external interruption.
 +
 +[{{ :state-machine.png |Figure 1: Event state machine.}}]
 +
 +NCL 3.0 EDTV profile defines the following types of events:
 +
 +  * presentation event: defined by the presentation of a subset of
 +    information units of a media object content.  Presentation events are
 +    specified in NCL on [[area|<area>]] elements, or on media nodes themselves
 +    (on their whole content anchors).  Presentation events may also be
 +    defined on composite nodes (represented by [[body|<body>]], [[context|<context>]],
 +    or [[switch|<switch>]] elements), representing the presentation of information
 +    units of any node inside the composite node);
 +
 +  * selection event: defined by the selection of a subset of information
 +    units of a media object content being presented.  Selection events are
 +    specified in NCL on [[area|<area>]] elements, or on media nodes themselves
 +    (on their whole content anchors);
 +
 +  * attribution event: defined by the attribution of a value to a property
 +    of a node (represented by a [[media|<media>]], [[body|<body>]], or [[context|<context>]]
 +    element), which must be declared in a [[property|<property>]] child element of
 +    the node; and
 +
 +  * composition event: defined by the presentation of the structure of a
 +    composite node (represented by a [[body|<body>]], [[context|<context>]], or
 +    [[switch|<switch>]] element).  Composition events are used to present the
 +    composite map (composite organization).  This functionality is optional
 +    in EDTV/BDTV profiles.
 +
 +
 +==== Syntax ====
 +^ Element ^ Attributes ^ Content ^ Parent ^
 +| [[causalconnector|<causalConnector>]] | __//id//__ | ([[connectorparam|<connectorParam>]]*, ([[simplecondition|<simpleCondition>]] <nowiki>|</nowiki> [[compoundcondition|<compoundCondition>]]), ([[simpleaction|<simpleAction>]] <nowiki>|</nowiki> [[compoundaction|<compoundAction>]])) | [[connectorbase|<connectorBase>]] |
 +==== Attributes ====
 +
 +^ Name ^ Value ^ Description ^
 +| //id// | It may receive any string value that begins with a letter or an underscore and that only contains letters, digits, <".">, and <"_">. | The //id// attribute uniquely identifies the element within a document. |
 +
 +
 +
  
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