Point Datatypes

Brick does not provide explicit separation of the point classes by datatype. This poses a problem for visualisation, analytics, and other downstream uses. It is therefore necessary to explicitly state the datatype expected for a particular point.

note

There is particular ambiguity around the definition of command points. See here for more detail: Command: ENUM vs Analog

Overview

Summary of datatypes per point class/sub-class.

Point Type	Datatype	Detail	Allowable Datatypes
Status	Boolean	default	Boolean, Complex
↳ Mode Status	EnumeratedValue	default	EnumeratedValue
Sensor	Numeric	default	Numeric, Complex
Setpoint	Numeric	default	Numeric, Complex
Command	Numeric OR Boolean	manual	Numeric, Boolean, Complex
↳ Mode Command	EnumeratedValue	default	EnumeratedValue

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Detail

Standard Datatypes

For the following point types, the datatype defaults to:

• Status
  datatype = Boolean
• Sensor
  datatype = Numeric
• Setpoint
  datatype = Numeric

For the following sub-types, the datatype will default to:

• Mode Status
  datatype = EnumeratedValue
• Mode Command
  datatype = EnumeratedValue

It is possible to manually set or override the default datatype for each point; however this should not be a regular requirement. The list of available datatypes is restricted by point class.

The following point types always require manual selection of their datatype:

• Command
  datatype = Boolean OR Numeric

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Complex Datatype

Certain point types and data sources may provide data in a non-standard manner. The complex datatype is a flag to indicate this. Processing may vary on a point & source basis.

For example, an Occupancy Tracking Sensor point may provide a list of user_ids present in the observed zone as its value per observation:

timestamp = 2022-11-20_221045.444Z0
value = [ user_11234, user_54234, user_2224 ]

timestamp = 2022-11-20_221145.137Z0
value = [ user_11234, user_54234 ]

...

note

The complex flag is a placeholder for additional sensor types and datastreams that are currently unknown. It is likely that this concept will be expanded upon in future.

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RDF Defintion

We will use the brick entity properties concept to capture the datatype and any associated metadata, such as references or definitions for enumerations.

:subject a brick:point_class ;
    brick:datatype [
        brick:value qudt:data_type ;
        brick:states :enum_1 ; # This is optional; Only valid for Enumerated and Boolean datatypes; :enum_1 a qudt:Enumeration
    ] .

Examples

Sensor

:point_1 a brick:Position_Sensor ;
    brick:hasUnit unit:Percentage ;
    brick:datatype [
        brick:value qudt:NumericType ;
    ] .

Status

:point_2 a brick:Position_Status ;
    brick:hasUnit unit:Unitless ;
    brick:datatype [
        brick:value qudt:BooleanType ;
    ] .

Mode Status

:point_2 a brick:Position_Mode_Status ;
    brick:hasUnit unit:Unitless ;
    brick:datatype [
        brick:value qudt:EnumeratedValue ;
        brick:states :enum_1 ; # where :enum_1 a qudt:Enumeration 
    ] .

Command

Datatype needs to be manually set.

:point_3 a brick:Position_Command ;
    brick:hasUnit unit:Unitless ;
    brick:datatype [
        brick:value qudt:BooleanType .     # this point is a boolean position: OPEN | CLOSED
        brick:states :bool_1 ;
    ] .

# NEED TO FIGURE OUT HOW TO DEFINE THIS
:bool_1 a qudt:Enumeration ;
    brick:hasStates [
            a qudt:BooleanTypeEnumeratedValue ;
            meta:key 0;
            meta:value "OPEN"
        ] [
            a qudt:BooleanTypeEnumeratedValue ;
            meta:key 1;
            meta:value "CLOSED"
        ]
    ] .

:point_4 a brick:Position_Command ;
    brick:hasUnit unit:Percentage ;
    brick:datatype [
        brick:value qudt:NumericType .     # this point is a Numeric position: %
    ]

Mode Command

:point_5 a brick:Position_Mode_Command ;
    brick:hasUnit unit:Unitless ;
    brick:datatype [
        brick:value qudt:EnumeratedValue .
        brick:states :enum_1 ;                  # reusing the Enumeration definition from point 2
    ] .

Setpoint

:point_6 a brick:Position_Setpoint ;
    brick:hasUnit unit:Percentage ;
    brick:datatype [
        brick:value qudt:NumericType .     # this point is a Numeric position: %
    ] .