Hi Steve,
Thanks for asking questions,please find the answers
1. How do you know that there will be a historian sample for each tag at the exact date/time you request?
Ans: At shop floor we have various tanks used in Manufacturing, Blending etc. Attributes(Net Mass, Temperature, Volume of material) of this tanks changes with time. User completes the process through different interfaces by capturing values of these tanks, Manufacturing steps takes time so situation arise that something has been completed 1-2 days back but user wants to close the steps today, in these type of scenarios we need to get the exact values of tags at the exact time when that tank was being used.
2. Which historian(s) do you currently connect or plan to connect to?
Ans : Its the PHD
3. Do you have the ability to do this type of query outside of PCo/MII currently?
Ans: At present we can pass the XML structure with different tags with different times to PHD via web service call request and we get the values of all the tags in one XML structure in response
