HistorianAbout a Historian Model
A Historian model is a hierarchical classification of various objects in a system. A
model contains the following components:
- Object Types
- Contained Types
- Object Instances
- Variables
Object Type: An object type is a blueprint, which you want to replicate that will
have a common structure (common properties/attributes and contained types). These object
types can be the products you manufacture, your assets, byproducts, or anything else for
which you want to classify information hierarchically and inherit properties/attributes.
For example, in an automobile manufacturing unit, the vehicles you manufacture are
object types (for example, a car or a scooter).
Contained Types: A contained type is an object type that you can include in
another object type. For example, suppose you manufacture cars with the following types
of engines:
- Petrol
- Diesel
When you create an object type for a car, you can include any of these contained types.
You can include multiple contained types in a single object instance. In addition, you can include a single contained type in multiple object instances.
Object Instances: Each item of an object type that you manufacture is called an
object instance. For example, if you manufacture three cars, each one is an
instance.
An object instance is specific to a Historian system. An object type, however, is not associated with a system.
Variables: Each attribute or property of an object is called a variable. These
variables are common across all objects of a certain type. They represent tags whose
values are collected by data collectors. For example, a car can have the following
variables.
When you create instances of an object type, by default, the variables in the object type are inherited to all the instance as well. You can choose to include or exclude one or more of these variables for each instance.
When you create instances of an object type, by default, the variables in the object type are inherited to all the instance as well. You can choose to include or exclude one or more of these variables for each instance.
In the following image, all the variables of the car object type are inherited to each of
the instances. However, the first two instances do not include Storage. And the third
instance does not include Mileage and Fuel Type.
If an object type contains contained types, the variables in the contained types are inherited as well.
If an object type contains contained types, the variables in the contained types are inherited as well.
After you create an object instance, you must store the values of each variable of the instance. To do so, you must map each variable with a Historian tag or create one, depending on the type of the variable.
Types of Variables:
- Direct: Tags for these variables are created in Historian when you select a collector instance. For instructions on collecting data for these types of tags, refer to Collect Data for a Direct Variable.
- Indirect: These variables are mapped with existing Historian tags. For instructions on collecting data for these types of tags, refer to Collect Data for an Indirect Variable.
- Static: These variables have a static value, which you provide when you create an object instance. For instructions on providing data for these types of tags, refer to Provide Data for a Static Variable.
Limitations:
- An OPC UA model is not supported.
- If using an iFIX model on the same machine, you cannot use a Historian model.
- If the name of a tag associated with a variable in a model contains a period (.), you cannot import the tag while importing the model into a Historian system.