| 类（全部继承自DataItem） | 描述 |
|---|---|
| Event | an alias for DataItem |
| Sample | a data item with a floating point value |
| Message | an event with an additional native code. The text of the message is the value. |
| Condition | A condition handles the fact that a single condition can have multiple activations and needs to check when the are present and are cleared. |
| Active | The Activation is itself a data item. This is so it can be cleared and treated like other data items when generating text. |
| TimeSeries |