HDF5 OPeNDAP Project Update and Demo MuQun Yang and Hyo-Kyung Lee (The HDF Group) James Gallagher (OPeNDAP, Inc.) 1 HDF and HDF-EOS Workshop XII 10/17/2008
HDF5 OPeNDAP Project Update and Demo
Feb 23, 2016
HDF5 OPeNDAP Project Update and Demo. MuQun Yang and Hyo -Kyung Lee (The HDF Group) James Gallagher ( OPeNDAP , Inc.). OPeNDAP Review . A software framework that allows simple access to remote data Data Access Protocol Client-server model Widely used by Earth Science Community. - PowerPoint PPT Presentation
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HDF5 OPeNDAP ProjectUpdate and Demo
MuQun Yang and Hyo-Kyung Lee (The HDF Group)
James Gallagher (OPeNDAP, Inc.)
1HDF and HDF-EOS Workshop XII10/17/2008
OPeNDAP Review
• A software framework that allows simple access to remote data
• Data Access Protocol• Client-server model• Widely used by Earth Science Community
2HDF and HDF-EOS Workshop XII10/17/2008
Client Library(libnc-dap)
DAP Proctocol (Internet)
Server(apache)
Handler(hdf4_handler)
Visualization tools
(e.g. GrADS)
Data(HDF4)
View Data (User)
OPeNDAP Concept
3HDF and HDF-EOS Workshop XII10/17/2008
Visualization Tools
(gradsdap)
Example Usage
OPeNDAP Client
OPeNDAPHDF4 Server
HDF4
Syntactic Structure of DataSemantic Meaning of Data
Actual Content of Data
OPeNDAP Visualization Client4HDF and HDF-EOS Workshop XII10/17/2008
Why is HDF5-OPeNDAP Project important?
• HDF5: NASA EOS / NPOESS
• NASA’s MISSION: ACCESS!
• Our MISSION: Build a DAP-HDF5 Bridge
5HDF and HDF-EOS Workshop XII10/17/2008
OPeNDAP HDF5 Server
1. Map HDF5 Datatypes to DAP Datatypes
2. Plus, some enhancements to allow OPeNDAP Clients to access HDF-EOS5 Files
Goal: Access HDF5 data via OPeNDAP
6HDF and HDF-EOS Workshop XII10/17/2008
Mapping HDF5 Datatypes to DAP Datatypes
• Compound Datatype
• Support for Group
• Object/regional References
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Challenges
Some OPeNDAP Clients
• Need special variable names and attributes on dataset.
• Need shared geolocation variables outside Grid.
Not all OPeNDAP clients are created equal!
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Tweaks for OPeNDAP Clients
Two server configuration options• --enable-short-name• --enable-CF
9HDF and HDF-EOS Workshop XII10/17/2008
HDF EOS5
• Grid with No Geolocation data Clients expect Grid with Geolocation data
• Some Attributes stored as Extremely Long String(s) (e.g. StructMetada.0) Clients expect structured attributes
Not all HDF5 files are created for DAP!
10HDF and HDF-EOS Workshop XII10/17/2008
Tweaks for HDF-EOS
Two more server configuration options• --enable-eos-grid • --enable-eos-meta
11HDF and HDF-EOS Workshop XII10/17/2008
Day After Server Tweaks
• Finally, Happy Clients!
GrADSNCLFerretMATLAB
ncBrowse
IDVODC
IDL
12HDF and HDF-EOS Workshop XII10/17/2008
Goals
•1st: Access HDF5 via OPeNDAP o The OPeNDAP HDF5 handler was released in March, 2008 at OPeNDAP website http://opendap.org/
• 2nd: Construct HDF5 data from OPeNDAP Bonus: Help clients to better access EOS Swath data
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HDF5-Friendly OPeNDAP client library
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Example: Groups in HDF5Traditional OPeNDAP client library: It’s an attribute that I don’t understand. I’ll ignore it.
HDF5-Friendly OPeNDAP client library: I was waiting for this key attribute to re-construct HDF5
15HDF and HDF-EOS Workshop XII10/17/2008
Example: Reference in HDF5
• Important for NPOESS• Object / Regional Reference • Map to DAP URL
16HDF and HDF-EOS Workshop XII10/17/2008
• Only ODC can display Swath properly.
• One more reason: Help Clients to view Swath
HDF5-Friendly OPeNDAP Client Library
No Latitude and Longitude
Courtesy of NASA
17HDF and HDF-EOS Workshop XII10/17/2008
libnc-dap
???
liboc-dap
NetCDF OPeNDAP Client Library
libdap
Dap server
OPeNDAP NC Server
gradsdap
NetCDFView NetCDFHDF5
Group/Ref/Swath
OPeNDAP HDF5 Server
View HDF5
gradsoc
View G/R/Swath
HDF5-Friendly OPeNDAP Client Library
18HDF and HDF-EOS Workshop XII10/17/2008
Summary of Client Library Prototype
• Finished coding • Tested with the GrADS visualization
client• Documented • Working on a demo DAP to HDF5
tool by using the client library prototype
• Will test with NCL if time allows
10/17/2008 HDF and HDF-EOS Workshop XII 19
Example: dap2h5
• A test application for the client library• It can construct HDF5 from DAP output
ORIGINAL
CONSTRUCTED
20HDF and HDF-EOS Workshop XII10/17/2008
Demo: MLS swath via GrADS
• GrADS coupled with our client library
• The client library provides grid mapping from swath data
• GrADS displays swath through HDF-EOS5 specific client library API calls
21HDF and HDF-EOS Workshop XII10/17/2008
Caution
• Our Client Library is ONLY PROTOTYPE! It does NOT support all DAP data types It does NOT support all AURA files It does NOT support all Visualization clients
22HDF and HDF-EOS Workshop XII10/17/2008
Summary
• HDF5 Access via OPeNDAP Is Easy Is used by GES DISC to serve Aura files
• HDF5-Friendly OPeNDAP Client Library Prototype Serves HDF5 better(EOS swath) Benefits visualization clients
23HDF and HDF-EOS Workshop XII10/17/2008
Future Work
• HDF5 to DAP2 Mapping Document• Release HDF5-friendly OPeNDAP Client Library Prototype
• URL: http://hdfgroup.org/projects/opendap
24HDF and HDF-EOS Workshop XII10/17/2008
Credits
Mike Folk (The HDF Group)Robert McGrath (NCSA)
Peter Leonard, Daniel Kahn, Marghi Hopkins (ADNET)Christopher Lynnes, James Johnson, Denis Nadeau, Fan Fang
(NASA)Jennifer Adams (GrADS)
Dave Brown (UCAR)
25HDF and HDF-EOS Workshop XII10/17/2008
Acknowledgement
This work was supported basing upon the Cooperative Agreement with the National Aeronautics and Space Administration (NASA) under NASA grant NNX06AC83A and NNX06AG75A. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of NASA.
26HDF and HDF-EOS Workshop XII10/17/2008
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