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NcObject

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NcObject is the base abstract class from which all other NCA classes must inherit from.

The properties of NcObject are listed in the following table.

Property Name Datatype Readonly Description
classId ncClassID Yes sequence of numeric class identifiers or authority keys
classVersion ncVersionCode Yes class version represented according to Semantic versioning guidelines
oid ncOid Yes unique object id
constantOid ncBoolean Yes flag to indicate if the oid is constant or not
owner ncOid Yes unique object id of the parent
role ncRole Yes unique role of the object within the containing block
userLabel ncString No user definable label
lockable ncBoolean Yes flag to indicate if the object can be locked
lockState ncLockState No current lock state of the object
touchpoints sequence Yes sequence of touchpoint (see Touchpoints section for details)

The role is a structural identifier which MUST be persisted across restarts. The role path of an element can be constructed of its role and the roles of all its parents. The role path can then be used to target a particular section of the control model tree or to retrieve the object ids again after a restart.

Object ids (oid property) may be constant across system restarts in which case they MUST be signaled using the constandOid property by settings its value to true.

Generic getter and setter

NcObject offers two generic methods for retrieving and setting a property on an object.

The get method ([element("1m1")]) accepts ncPropertyId (which is a pointer for ncElementID) as an arguments and returns ncMethodResultPropertyValue.

// CLASS ELEMENT ID  
interface ncElementID {
    attribute ncUint16 level;
    attribute ncUint16 index;
};

typedef ncElementID ncPropertyID;

ncMethodResultPropertyValue inherits from ncMethodResult but can return any value type depending on the underlying property type.

interface ncMethodResultPropertyValue : ncMethodResult { // property-value result
    attribute any value;
}

The set method ([element("1m2")]) accepts ncPropertyId and any value (type depends on the underlying property type) as arguments. The return type is the base ncMethodResult.

PropertyChanged event

NcObject offers a PropertyChanged event [element("1e1")] which MUST trigger anytime a property on the object is changed. The event data is of type ncPropertyChangedEventData which MUST include the property id, property value and the change type.

interface ncPropertyChangedEventData {
    attribute ncPropertyID propertyId; // ID of changed property
    attribute ncPropertyChangeType changeType; // Mainly for maps & sets
    attribute any propertyValue; // Property-type specific 
};

enum ncPropertyChangeType {// Type of property change
    "currentChanged", // 0 Scalar property - current value changed
    "minChanged", // 1 Scalar property - min allowed value changed
    "maxChanged", // 2 Scalar property - max allowed value change
    "itemAdded", // 3 Set or map - item(s) added
    "itemChanged", // 4 Set or map - item(s) changed
    "itemDeleted" // 5 Set or map - item(s) deleted
};

Events can only be consumed as notifications when subscribed to in the SubscriptionManager. See the Managers section.

Working with collections inside an ncObject

Collection types are defined as webIDL sequences of a specific type. There are generic methods for getting, setting, adding and deleting items inside a collection property as part of ncObject.

Getting a collection item is done through the getCollectionItem method ([element(“1m4”)]) by specifying the property identifier (ncPropertyId) and the index as arguments. The result is of type ncMethodResultPropertyValue.

Setting a collection item is done through the setCollectionItem method ([element(“1m5”)]) by specifying the property identifier (ncPropertyId), the index and the value as arguments. The result is of type ncMethodResult.

Adding an item to a collection is done through the addCollectionItem method ([element(“1m6”)]) by specifying the property identifier (ncPropertyId) and the value as arguments. The result is of type ncMethodResultId32 which contains the index where the value was added.

Removing an item from a collection is done through the removeCollectionItem method ([element(“1m7”)]) by specifying the property identifier (ncPropertyId) and the index as arguments. The result is of type ncMethodResult.

Touchpoints

Touchpoints represent the way in which a control model object may expose identity mappings across other contexts. All ncObject may have touchpoints.

The ncTouchpoint class specifies a namespace and resources.

interface ncTouchpoint{
    attribute ncString contextNamespace;
    attribute ncTouchpointResource resources;
};

The ncTouchpointResource class MUST specify a resourceType and an id.

interface ncTouchpointResource{
    attribute ncString resourceType;
    attribute any id;
};

For NMOS namespaces there are derived types.

// IS-04 registrable entities
interface ncTouchpointNmos : ncTouchpoint{
    // ContextNamespace is inherited from ncTouchpoint.
    attribute ncTouchpointResourceNmos resources;
};

interface ncTouchpointResourceNmos : ncTouchpointResource{
    // ResourceType is inherited from ncTouchpoint. 
    attribute ncString id; // override 
};

// IS-08 inputs or outputs
interface ncTouchpointResourceNmos_is_08 : ncTouchpointResourceNmos{
    // resourceType is inherited from ncTouchpointResource
    // id is inherited from ncTouchpointResourceNmos
    attribute ncString ioId; // IS-08 input or output ID
};

For general NMOS contexts (IS-04, IS-05 and IS-07) the ncTouchpointNmos class MUST be used which has a resource of type ncTouchpointResourceNmos. This allows specifying the UUID of the underlying NMOS resource.

For IS-08 this is further derived to use a resource of type ncTouchpointResourceNmos_is_08. This allows linking to a UUID and an input or output id.

Architectural information about the touchpoints concept is available in the architecture document under the NCA-NMOS identity mapping section.

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