You map data items read from assets to usage items created in the Axeda® Platform. In addition to the name and model for the data item, you specify the "type" as cumulative, incremental, replenishable, recoverable, or counter. This type attribute determines the data item value presented by the associated usage item.
Incremental
- (Delta value) contains the difference in the value received from
the last value received for the related data item. For example, if
the first value received is 1, and the second value is 5, an Incremental
usage item contains the value 4.
If this type of usage item is associated with a counter, a reset of
the counter to zero causes the value of the item to be set to zero.
For example, suppose a counter represents the number of machine cycles
and is reset to zero when the machine is powered off. The counter
returns the values 1, 2, 3, 4, off (reset to 0), 1, 2, 3, off, 1,
2, 3, 4, 5. The value of an incremental usage item associated with
this counter is 4 - 4(the reset to zero) + 3 - 3 + 5, for a total
of 5. If you want to know the total number of machine cycles, use
the Counter type instead.
Cumulative - (Total or actual value) contains the actual, total value received for this data item. This value rises as new positive values are received and falls as new negative values are received. For example, if the first value received is 1, the second 2, the third 3, and the fourth -2, the cumulative usage item has a value of 4 after receiving the fourth value.
Recoverable - contains the actual value of the data item, which may rise or fall. For example, if this value tracks disk space, if the disk is almost full, the value is high; if the disk is cleaned and files are removed, the value falls.
Replenishable - contains the actual value of the data item; this value is expected to fall over time. For example, if this value tracks the fuel in a tank, at first the tank is full and the related value high; over time, as the fuel is used, the related value falls in kind. The importance of this usage item type is in its ability to track falling values.
Counter - contains a cumulative counter value, without subtracting all values when the counter is reset to 0. For example, suppose a counter represents the number of machine cycles and can be reset to zero when the machine is powered off. The counter returns the values 1, 2, 3, 4, off (reset to 0), 1, 2, 3, off, 1, 2, 3, 4, 5. The value of the usage item is 4 + 0 + 3 + 0 + 5 = 12.
You can create numerous usage items for a single data item.