Special extensions in Application Server objects
- Last UpdatedJul 17, 2024
- 2 minute read
The WindowMaker Tag Browser and the Message Exchange client in WindowViewer add and recognize special extensions to each Application Server object attribute. These extensions provide access to information that otherwise would not be available to the InTouch HMI.
These special extensions are optional and do not need to be used by the InTouch application. However, applications that handle status and quality information frequently need to use these extensions.
These items extend the namespace of attributes to include additional properties that WindowViewer can expose to application scripts and Windows. For example, the reference to "TIC101.PV.#ReadSts" provides access to the MxStatus information for the subscription to TIC101.PV. This information is very useful for displaying extended information that is exposed by Message Exchange.
These properties do not exist as object attributes in Application Server as named elements. The properties are client-side extensions, supplied in the client abstraction layer, that make object attributes visible to the InTouch HMI. The following table describes the attribute extensions for the InTouch HMI:
|
Attribute Extension |
Data Type |
Purpose |
|---|---|---|
|
None |
Coerced |
The default extension. Means that no extension is provided. The item is read/written with the value data type coerced as appropriate to InTouch. Failed read/write information can be obtained if the client subscribes to the #ReadSts or #WriteSts items described below. Example: "Pump1.PV". |
|
.#VString for floats / doubles attributes only: .#VString1 .#VString2 .#VString3 .#VString4 |
String (read/write) |
Sets up a subscription to the reference that has ".#VString" as a suffix. This is the underlying reference. Returns the current value of the underlying reference as a string when reads and writes are both working correctly. If the UserGetAttribute returns bad status, this item returns an abbreviated status description string based on MxStatus instead of the value. The abbreviated status description strings are: "?Pending" - pending "?Warning" - warning "?Comms" - communication error "?Config" - configuration error "?Oper" - operational error "?Security" - security error "?Software" - software error "?Other" - other error |
For .#VString, if the status is good but the quality is bad, this item returns the quality description string, available from Message Exchange, instead of the value.
The value is returned as a string only when quality and status for UserGetAttribute are both good or when the quality is good and the status is uncertain. This may require coercion if the data type returned by Message Exchange is not a string. When quality or status is uncertain, the value shows a "?" as a suffix. For example, "3.27?" or "True?".