Actual data points in the asset to which the Axeda® Platform can read and write data. Data items are configured for models, and a set of data items applies to all assets of a specified model (by model number). One or more data items can be mapped to a single usage item for use in analytics searches and calculation and scheduled rules that track use and run actions based on asset use.
Note: Data items are referred to as "properties" in the documentation for the Axeda® IDM Agents.
The Platform supports reading and writing to data items of the following types: analog (double), digital (Boolean 1 and 0), and string (alphanumeric). Data items are configured with attributes that affect their use in the Platform. The data item attributes are as follows:
Read Only -- The Platform cannot write values back to the actual data point in the data source. These data items are not visible when configuring a Set Data Item action.
Visible
-- When Visible is selected (the default), the data item appears in
the various Application pages; otherwise, the data item and its value
are hidden from view. If data items are configured as Not Stored,
they are automatically Not Visible
and available only in the Package wizard; however,
they can be used in custom object scripts and in expression rules
and other areas where free-form text is allowed.
Even though a data item is visible, your ability to "see"
the data item in the pages depends on your User Group's privileges
and assignments. For example, your user group needs to be associated
with the asset group in which the related asset is defined AND, if
your user group is associated with data item group(s), the specific
data item must be included in the data item group(s) assigned to your
user group.
Forwarded -- When Forwarded is selected, the Platform forwards values for this data item to a configured parent server (as defined in the Administration application).
Storage Options -- For this attribute, you can select among the following values:
No History -- Only the current (most recent) value of the data item is stored. Values are not stored in the history table in the database.
Stored -- Data is stored (persisted) in the Platform; both current and historical data are accessible. For a persisted data item that has a value larger than 4000 characters, the Platform truncates the value to 4000 characters before storing it.
On Change -- Data is stored (persisted) in the Platform only when the value changes so that only the last value of the data item is stored. This option is the default setting for newly created data items. (In the case of a migrated Platform, the Storage Option is left unchanged.) This setting allows you to maintain a history of transitions for a data item and know when its value was last read from the asset.
Note: For the Stored and On Change settings: For a persisted data item that has a value larger than 4000 characters, the Platform truncates the value to 4000 characters before storing it.
No Storage
-- Data is not stored at all. The current value of the data item
is NOT available, except to expression rules configured to run
based on the receipt of the data item. When you select this option,
the data item is not visible in the Asset dashboard (Data module),
nor can it be assigned to a Data Item Group. In addition, the
Visible attribute is automatically disabled.
When you select this option, the data item is not visible in the
Data module of the Asset dashboard or in the Current and Historical
Data pages of the Axeda® Service
application.
In addition, it is not available for selection for Data Item Groups,
for the Actions, SetDataItem and RequestDataItem.
However, it IS visible in the Package creation wizard, for Package
dependencies, Package instructions, and Package rollback instructions.
The Agents run the packages and have values for all data items
even though the Platform may not have stored the same data item
values. In addition, you
can use the data items in custom objects, expression rules, and
anywhere else in which you can enter free-form text (as opposed
to picking from a list in the UI).
Important! If you change a data item from storing data to not storing data and then back to storing data, any data replay for that period of time is lost. This means for absolute data replays, there will be historical (logged) data from before and then after with no logged data in between. This does not affect interval history, which is interpolated and does not show that loss of data.
You create data items for a model in the Model wizard pages. Privileges to view data values and write to asset data points are restricted to specified user groups.
For data items in the Axeda® Applications pages, you can:
view the most recent data values for an asset in the Axeda® Service Application, Asset dashboard Data module
view historical or current data values in the Axeda® Service application, charts or displays for the asset
configure a Data Expression rule that evaluates the values read from an asset and executes actions based on the results of that evaluation
configure a Set Data Item action that writes values to data items in an asset; run that action immediately from the Service application, Asset dashboard Actions module
configure a Request Data Item action that retrieves the value of a specified data item for an asset from its associated tracking asset
configure a Collect Data action that service technicians can use from the Asset dashboards to retrieve the current values of data items from an asset
configure a Data Entry action that service technicians can use from the Asset dashboards for selected models to set values for data items on the asset and/or in the Platform
map to a usage item used to track the number of uses (total counts or a change in counts) of that data item.
map to a maintenance item to track the need for preventive maintenance through the changing values of a data item
For information about security for data items, refer to Security for Objects in Axeda® Connected Product Management Applications and for information about security for these objects when Delegated Administration is enabled, refer to Security for Objects in Delegated Administration Units.