So the PI System is all about time really when it comes down to it. We've got time, so I'll just say
it's a little clock here. And then we have some value, and the PI System is able to essentially
record this value as it comes in, in real time. And also make an entire history available to
any user that wants to use it in a spreadsheet and just some kind of graph. Or in any kind of report.
The PI System is so adept at times, it's the big strength of it. I would go so far as to say that
the PI System is time. That's what it's all about as well as bringing in the infrastructure data
of your entire enterprise. And the reason it does this is because it does time really well.
OK, so you've heard me saw that PI does time really well. And one thing that you
might not be surprised about, because we do time so well, we have a particular way
of navigating time because we work in it all the time. And that is, how do I
refer to any particular spot in this graph? Now conventionally, what we usually do is we say,
well give me the time on Monday. And so I would then give you a particular date,
say Monday was the 23rd. So say 11-23 and Stuart is making up dates now. And you can
query a certain date and you'll get a certain value and that's that. So that's referring it
to a date. That's how we usually refer to things in the world. But one thing that often happens
with people working with data in the PI System is they want to know what's happening right now
and things that have just been happening. So I want to know what's happening right now and
I want to know about things that have happened since today started. That's what I want to know.
So that starts to become a little more complicated because now is happening,
it's always moving on. And also if now is always moving, if I want to move the last 8 hours,
that's always moving too. And so we have this moving frame going on. A frame of time that
is moving. And because of that we have special ways of referring to time in the PI System. Now
the first and foremost that you need to know is that this is OK. We can refer to times as dates,
that's alright. So if I want to refer to a time, I can refer to it as a date. Totally
OK. If I want to refer to what's going on right now, I can do that too. And I do that with an
asterisk. So in a number of different PI pieces of software, like PI DataLink, PI ProcessBook, PI
Coresight (now called PI Vision). PI WebParts. PI Data Access. Whenever we are actually asking the
server for data, we can usually use something like asterisks to refer to what's going on right now.
We can also use things like dates. And a wide variety of date formats are recognized.
Well particular date formats are recognized but you'll find that it is flexible enough
to not be annoying. You can put in certain fragments of a date and the PI System will
still be able to recognize it and work with it. Now these refer to particular dates in time,
particular spots in time. If I were to tell you 11-26-2013, you'd know what I was talking about.
If I referred you to right now, you'd know what I was talking about. Other things that
we have in the PI System, we can refer to today which is today, this morning at midnight. And we
can also refer to yesterday. And that's Y. That's yesterday morning at midnight. So today right now,
it's Friday and yesterday would be Thursday. So T would refer to Friday morning at midnight and
Y would refer to Thursday morning at midnight. And then tomorrow when tomorrow is Saturday,
T would refer to something new. T will now refer to something new. T will refer
to Saturday morning at midnight and Y will refer to Friday morning at midnight.
The power of these symbols right here is they are going to change and adapt as time marches
on. Whereas just a static date, while very useful, will always just be that date. Now
we refer to this with a particular type of name. We refer to these as absolute references meaning
if I were to give you one of these references, you would know what time I was talking about.
Even if that time is changing as time moves, you know exactly where I'm talking about.
Now this is contrast to the other type of time reference which is something called relative.
Now a relative time reference is something that you and I are all familiar with, it's something
like a minute, an hour, or a day. A day is a length of time, so all the relative references
are lengths of time. And in PI we have a couple of them. And they are hours, minutes, seconds, years,
and what else do we have? We have days, weeks. And they'd each have their own abbreviations. So
hours is H, minutes is M, seconds is S, years is Y, days is D, weeks is W. And there is also months
which is MO. So all of these are relative time references. And the difference between a relative
time reference and an absolute time reference can be summed up with me saying, OK when is today?
But if I were to say when is minutes? Or when is days? That doesn't refer to something. But
now I can combine these two to make a powerful time reference. So I can say something like what
was the value 8 hours ago? And that would be.. Let me write it down so we can all see it. So
if I want to know 8 hours ago, that would refer to.. I can probably say that's now - 8 hours.
And this refers to 8 hours ago in PI short hand. I could also say something like let's say yesterday
at 8AM. How would I refer to yesterday at 8AM? Remember yesterday is always changing. Tomorrow
is going to be a different yesterday. I would refer to that.. And there might be a few different
ways of doing it. I would say Y for yesterday and then probably + 8 hours. That's yesterday morning
at midnight plus 8 hours, equals 8PM. If I know that there is a particular date and a particular
time -- so I want to know on December 25th of last year at 6AM, I want to know what the value was?
Well now for that, we are going into a very specific date. So I can start using a specific
date. I could say, 12-25-2012 and then I'd write in, space, 6 o'clock. Now we can also short hand
this if you just wrote in 6 o'clock, that would work as well. Now there are a few other ways that
the time-stamps are interpreted. So for instance, if I were to not write in the years here,
if I were just to write 12-25 with no year, which 12-25 is it going to be?
Now this is an overview of how.. So this is an overview of how PI interprets time. We have
a number of different short hand, absolute and relative set. And you can combine these
together to refer to times anywhere in the whole time continuum of a PI tag -- going back to when
it started. Now usually these two time periods are paired, it's a time period, so I have a start time
and an end time. Now usually when we want to refer to that and we want to actually see a range of
data. So often that means we'll have a start time and an end time. So what that means, if I wanted
to see the last 8 hours, or let's say the last 2 hours, I would say * for right now, til * - 2
hours. And this becomes a time-range that I'm then looking at. It becomes the window. And if I were
to have a chart, then the far part of my chart is going to be now. And the end part is going to
be two hours ago. So this time range becomes the last two hours when I ask for it in that fashion.
So again, the PI System is time. It stores data really well. And we have a short hand system
to make querying time really easy and really fast. There is other ways of querying time in
tools like Excel. And Excel with PI DataLink, you can use either the Excel time or PI time,
which ever you are more comfortable with. We of course find that our short hand system is
really effective for referring to pieces of time and relative distances. But you can use
either time system that you are comfortable with there. But in all of the PI System products,
this form of PI time references is found and it really behoves you
to become familiar with it. So thank you very much and good luck navigating time.