Re: 20051220: NcML Aggregation in THREDDS

• To: Bjørge Solli <bjorge.solli@xxxxxxxx>
• Subject: Re: 20051220: NcML Aggregation in THREDDS
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Wed, 21 Dec 2005 11:15:38 -0700

Bjørge Solli wrote:

Hi John,

John Caron wrote:

Since you are explicitly writing the netcdf elements, we were expecting that you could write the correct values there without having to translate through a DateFormat. Is that not so? (see below also)

I guess so, but usually I try to use already implemented ways instead of doing a script on it myself. Less maintainence that way. So there is now way of doing this in the current version?

nope, sorry

Unidata Support wrote:

------- Forwarded Message

To: support@xxxxxxxxxxxxxxxx
From: =?ISO-8859-1?Q?Bj=F8rge_Solli?= <bjorge.solli@xxxxxxxx>
Subject: NcML Aggregation in THREDDS
Organization: Nansen Environmental and Remote Sensing Center - Bergen
Keywords: 200512201217.jBKCH47s009594 THREDDS NcML aggregation

Hi,

I am currently rewriting our xml-files to use the new aggregation functionality in Thredds 3.4. I have looked over all the documentation I could find on thredds and NcML but still have one unansvered Q. Hope you can help:

In the old version we used AggServer with an xml-statement like this:
...

<aggregation serviceName=".." aggType=".." varType=".." varUnit".." dateFormat="yyyy/M/d:hh:mm:ss z"> <fileAccess urlPath="long_name_b20030604_f200305289999.nc" coord="2003/05/28:00:00:00 GMT" />

   ...
...

My remaining Q is where I should write dateFormat now. I have something like this:

...
<variable name="time" type="int" shape="time">
   <attribute name="units" value=".." />
   <attribute name="_CoordinateAxisType" value="Time" />
</variable>

Here you are defining a time coordinate of dataType "int"

I see I omitted the units-value, it is "secs since 1970-01-01 00:00:00". This is a value I don't think my research coworkers want to change since I understand it is some standard in their field. The one in charge are on holidays, so will have to wait till he's back for the definite answer.

yes thats a udunit string, which thredds also uses.
but if you use this, then you must write the correct integer values in the 
coord field.

<aggregation dimName="time" type="joinNew">
   <variableAgg name="T" />

netcdf location="long_name_b20030604_f200305289999.nc" coord=""2003/05/28:00:00:00 GMT" />

But you are giving it String values.

I guess I could give it int-values, but that would remove readability.

true, so the ISO 8601 date strings would work better.

Do you have the ability to write ISO 8601 date strings? If so, I would change the type of the time coordinate to String and do that.

Thanks for the advice, I will discuss it with my coworkers.

Since I am not using the scan tag I cannot use the dateFormatMark either (which would not work on this example anyway since the filename is not the same in front of the #-mark, which would have to be after the '_f').

We will also add regular expression matcher for that case.

Regexp is good! Is it possible to use it directly in the xml?

BTW: I'm a programmer, not a researcher, so I don't think I fully understand the implications a change like the one you suggested would have.

Thankyou.
Regards

• References:
  • Re: 20051220: NcML Aggregation in THREDDS
    • From: John Caron