Basic Basic Concept: Identity and the Compound Identifier
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The Properties property is a collection of ContextItem objects. This is how we can supply additional information needed to use the definition correctly. For example, if a ContextItemDefinition involves capturing values for latitude & longitude, it might include in the Properties a ContextItem that indicates the geodetic datum is expected to be WGS84.
The NestedDefIds property is a collection of references to other ContextItemDefinition(s). This is only populated if ValueType is set to "Nested". Sometimes there are groups of data points that need to be collected together rather than individually. For example, the Public Land Survey System is composed of 4 pieces of data the Meridian, Township, Range, and Section. Each is defined as its own ContextItemDefinition, and is represented as ContextItems that are included by value in the NestedItems property of the PLSS ContextItem.
The Presentations property is a collection of Presentation objects. One of the challenges in collecting quality data is being able to make sure that it is entered properly.The Presentation object contains a "friendly" name description, regular expressions that define how the value is supposed to look when entered or displayed, and a list of GeoPoliticalContext objects that describe "where" this presentation is used.
EnumItems: How we support enumerated lists.
DefaultUOM: Unit of measure
AllowConversion: Can the value The EnumItems property is a collection of ContextItemEnumItem objects. This is how we encode the enumerated values for a ContextItemDefinition of ValueType "Enum". The ContextItemEnumItem contains some of the same properties that ContextItemDefinition does. Instead of having a Code property, it has a Value. This Value is expected to be unique within the domain of the ContextItemDefinition it is attached to. When creating a ContextItem using an "Enum" type ContextItemDefinition, the ContextItem Value property corresponds to the Value property of the selected ContextItemEnumItem.
The DefaultUOM property is an optional string describing the expected unit of measure. In an effort to foster the broadest appeal, UN Rec 20 codes will be the default vocabulary for expressing units of measure.
The AllowConversion property is an optional boolean value that is used in conjunction with the DefaultUOM. This serves as a flag to determine if the user can allow the value to be entered in a unit compatible with DefaultUOM, or does it have to be in the default units?TimeScopes: When this Definition was created, updated, are they required to use the default unit.
The TimeScopes property is an optional collection of TimeScope objects. This collection allows us to attach a variety of time-related attributes to the ContextItemDefinition. For example, TimeScopes can describe when this ContextItemDefinition was created, another when it was updated, and a third the date range it is valid for.
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