The Add Attributes dialog attempts to be intuitive and changes the data it asks for based on the the Data Type being created, the Data Storage method selected, and other elements as needed.
Data Types
The platform provides the following data types:
Boolean: true or false values.
Datetime: specific date and time stored and displayed using the UTC time zone ("+00").
Enumeration: a list of distinct values, usually configured in a key-value pair. When an Enumeration is selected, an is required. The type can be selected from the pop-out of the Enumeration grid. More about Enumerations
Event Object: a composite data type that contains a number of data fields. The 'event' part indicates something that occurs and finishes, implying a certain transientness. The 'object' refers to the structure of the data associated with the attribute. When creating an event object, the option to select a Type is presented. Event objects can based on a Type, in which case their data is stored as time-series data. If there is no type they are stored as static data.
Float: high-precision fractional values. When the selected is Float, the option to select a Measurement Unit for the data is presented.
GeoPoint: specifies the physical location of an object such as a Place. Represents an actual point on the earth. GeoPoints require latitude and longitude values. More about GeoPoints
Integer: whole (non-fractional) numbers. When the selected is Integer, the option to select a Measurement Unit for the data is presented.
Interval: duration of time display as hours:minutes:seconds.
String: a combination of any characters that appear on a keyboard, such as letters, numbers and symbols.
Reference: a reference to another object in the Model.
Data Storage
The Data Storage options are Time Series and Static.
Static data is data that is not expected to change over time. When the system asks for static data, it is the current value of the data that is returned. If the value of the data had ever changed, the timestamp, user and the action that occurred (eg. 'UPDATE') will be visible in the Audit log, but only the current value of the item is returned.
When the Data Storage type Static is selected, the user is prompted to enter a 'Config Value' for the data type. For example, a boolean data type with a static Data Storage value would prompt for True / False. An Enumeration data type will offer the set of enumerations that are pre-configured for the enumeration type. A Geo Point allows entering the Latitude and Longitude for the point, along with a Show Map feature to see the plotted location.
Interval data types allow you to set a static interval in days, hours, minutes and seconds.
Most other data types allow entering any config value that adheres to the Data Type selected: if the data type is an Integer, integer values can be entered, same with a Float.
Time Series data is data where the value of the data is expected to change. As such, the data is stored with a value, a status and a timestamp, where the status is OPC UA quality data. When the Data Storage type is Time Series, the Data Source becomes important. The options are Tag, Internal and Expression.
- 'Tag' data is data from an external system, and carries a tag name that originates in the external system - usually an historian - that is mapped onto an attribute in the Model. In the external system the tag name may be obscure, cryptic or difficult to identify; when mapped onto an object in Model, the context makes the mapping understandable.
- 'Internal' data type indicates that the data is expected to change because something changes it from within the platform. This is usually the result of a script. The script may run several times a day: it might perform calculations, import data from an external system, or other actions, and then write new data into the system, including a value, timestamp and quality.
- 'Expressions' are essentially a specialized form of the Internal data source. When an expression is the Data Source, the data is potentially changed based on doing arithmetic on the data, calculating data from based on other data. Expressions are always evaluated as they are retrieved from storage.
When the data storage type is time-series:
- Expiration Interval is optional. The Expiration Interval is the maximum amount of time an attribute value is valid before updated, renewed, or replaced.
- Interpolation Method is required for all attributes except Reference. A default interpolation method is set based on the data type of the attribute.
- Range is not required for Time Series floats, integers, or intervals, but the Attribute Grid will warn that a Range does not exist for an attribute of this type. When a Range does exist, the Attribute Grid will use this data to draw a linear gauge in the Value column, providing a visual indication of the state of the attribute.
- Limits are not required for time-series data, but together with Range, they can provide a rich, visual clue as to the state of the attribute. Note that the Limits set the Lo, LoLo, High and HighHigh for the value, as well as a target value.
see also: Attributes