1. XML Via SOAP & Local Degrib Applications
Arthur A. Taylor
Meteorological Development Laboratory
NWS NDFD Technical Workshop November 2, 2006

2. Why Use XML Existing technology Facilitates additional processing
Extensible Markup Language is widely used (W3C specification)
De Facto standard for internet data exchange
Infrastructure exists (validators, XML Schema, etc.)
Facilitates additional processing
XML tools (XSLT, SAX, DOM) facilitate value added applications
Web application developers familiar with tools
Schema precisely defines a language
Reaches new users

3. Communicating Process
XML on the Move
Data Broker
(UDDI)
WSDL
Internet
SOAP Request
SOAP Request
Data
Consumer
(Client)
Provider
(Server)
SOAP Response
SOAP Response
Communicating Process
Discovery
(UDDI)
Description
(WSDL/Schema)
Messaging
(SOAP)
Transport
(HTTP)

4. The SOAP server
The experimental (becoming operational Dec. 4) XML via ‘Simple Object Access Protocol’ server provided by the NWS does the following:
Once an hour:
Download the NDFD GRIB2 files
Convert the GRIB2 files to data cubes
Upon request from the SOAP server:
PHP code parses the request
degrib_DP probes the data cubes
PHP code reformats it into XML
Note: Sometime after Dec. 4, all formatting will be done by degrib C code.

5. SOAP Server Lessons Learned
“If you build it, they will come”

6. Motivation Why add DWML capability to degrib?
Alleviate pressure on the XML server
allows whole sale users to use the GRIB2 files to create XML, using their own machines, for as many points and as often as they desire.
Speed up the server
Migrates from a scripted language (PHP) to a compiled language (C)
Provide the source code for the logic behind DWML
(c:\ndfd\degrib18\src\dwmllib\xmlparse.c)
Encourage the use of DWML

7. Overview To create NDFD DWML on a PC we need to
Download the NDFD GRIB2 to our PC
Probe the data at a given location
To enhance the speed of probing, we can also
Convert the data to a data cube
Probe the data cube at a given location

8. Attaining software To get the degrib program, go to:
For MS-Windows, use “degrib-install.exe”
By default this installs to c:\ndfd\degrib18
For UNIX, use “degrib-src.tar.gz”
By default this expand to “/degrib”. To compile it:
cd /degrib/src
make –f makefile.* (* is replaced by your operating system)

9. Get Data Option 1: Use “tkdegrib” or “tcldegrib web.tcl”
Advantage: In addition to downloading the data, it checks for data corruption, by performing an inventory.
From a command Prompt:
cd c:\ndfd\degrib18\bin
tcldegrib web.tcl –dataSet ndfd –sector midatlan –day d17 –variable all
Option 2: Use your own “URL get” program
To determine the locations of the NDFD GRIB2 files:

10. Probe Data For more details on probe options, see:
From a command prompt
cd c:\ndfd\degrib18\data\ndfd\midatlan
..\..\..\bin\degrib . –P –pnt 38.98, –XML 1 –geoData c:\ndfd\degrib18\geodata
The –geoData option supplies a directory to look in for information about the point’s timezone
For multiple points, either provide multiple –pnt options, or use the “-pntFile” option

11. Flavors of DWML
-XML 1 (or time-series) creates the time series product
User can choose to format any combination of the following: maxt, mint, pop12, temp, wdir, wspd, td, sky, qpf, snow, wx, waveh, apt, rhm
-XML 1 -Icon 1 will return just the icon information.
Requires: temp, wspd, sky, wx
Formats: icons
-XML 2 (or glance) is the glance product
Requires: maxt, mint, temp, wspd, sky, wx
Formats: maxt, mint, sky, wx, icons
-XML 3 (or 12-hourly) is the 12 hour summary product
Requires: maxt, mint, pop12, wdir, wspd, sky, wx
Formats: maxt, mint, pop12, wx, icons
-XML 4 (or 24-hourly) is the 24 hour summary product

12. Convert to data cube
The data cube consists of uncompressed data, which allows faster access than the GRIB2 files
Method 1 (use c:\ndfd\degrib18\bin\MakeData.tcl):
cd c:\ndfd\degrib18\bin
tcldegrib MakeData.tcl c:\ndfd\degrib18\data\ndfd\midatlan c:\ndfd\degrib18\cube\ndfd\midatlan
cd ..\cube\ndfd\midatlan
Method 2: Manual method
cd c:\ndfd\degrib18\data\ndfd\midatlan
..\..\..\bin\degrib maxt.bin –Data –Cube –Index maxt.ind –msg all
Repeat for all GRIB (*.bin) files.

13. Probe the data cube From a command prompt either:
..\..\..\bin\degrib . –DP –pnt 38.98, –XML 1 –geoData c:\ndfd\degrib18\geodata
..\..\..\bin\degrib_DP . –DP –pnt 38.98, –XML 1 –geoData c:\ndfd\degrib18\geodata
-DP is for probing a data cube, while -P is for a GRIB file
degrib_DP is compiled with just the data cube probing code so it is smaller than degrib

14. Credits I’d like to acknowledge: John Schattel for developing DWML
Paul Hershberg for converting the PHP code to C.