Roger Palmen

PI Clients and their call to DataReferences: GetValue or GetValues?

Discussion created by Roger Palmen on Aug 30, 2013
Latest reply on Sep 3, 2013 by Marcos Vainer Loeff

Hi All,


Especially after reading this whitepaper, i was left to wonder how a client retrieves data from an AF attribute. Does it use GetValue or GetValues? Using which timestamps.




Let's use an example: a PI WebParts Page with a time webpart, a trend webpart and a value webpart. Both webparts display the value of an attribute configured to use one of my Custom DR's. If i set the timerange webpart on the same page to *-1d and *, what calls are made to the DR for:

  1. the value webpart?  Obviously it returns one value only, but for a single time or a timerange passed through GetValue?
  2. the trend webpart? It returns interpolated values. If RDA methods supported, will it call PlotValues? If not, subsequent calls to GetValue for each pixel (as explained in the WhitePaper)? Or?
Ofcourse the same questions can apply to e.g. a ProcessBook display, Coresight, etc.
Unfortunately my workweek ran out of time to do some debugging to find out myself.