What do object tags do?
Object Tags allow symbols and their Instances to be grouped into types within their class.
Class Sub Type might be a better name, or SubClass.
They provide a means to sub divide the data associated with a class and to make the data that is common to types of objects store with the type rather than each instance, so that the data is entered and stored once, making a more efficient database.
Another way of looking at this is to see a class as containing any number of 'generic objects', and instances of those objects.
If in Data Design, the field 'Apply to Instance' is not set then when ControlDraw builds the data tables, the field is stored with the Object Tag. So this data becomes Type data applying to the 'generic objects'
Are object tags needed?
It is not essential to use them at all, and for simpler models they do not add much. However, they are required by the database structure.
It is recommended that the object tag rule be set to Text Value unless there is a need to store such type data. This will make sure that only one object tag is created for the class.
How many object tags?
Object Tags are created by scanning all the symbols on all the pages in the model and adding a record for each unique object tag that is found with a symbol whose class is included. Special Symbols are excluded.
So the total number is at least as many as there are included classes. And any of the objects in a class have different object tags then more.
NOTE - Object Tags must be unique - even across classes. So it is best to have a rule starting with the SymbolDefault Tag for the class, as this is always unique
How are object tags assigned?
They can be manually entered if the rule permits.
>Edit >Select Similar >Object tag
With this you can select all the objects on the current page that have the same object tag. this is useful for reviewing the model and for making changes to all the objects of the same type, for example, you could then make them all the parent of the same object.
Measurement Analog Class
This class is typically used for Transmitters, Flow, Level, Pressure etc.
By using the Page Tag stripped of numbers rule with a model containing FT01, FT02 etc and PT01, PT02 etc two objects are created, FT and PT so you have an object record for each measurement type