hdf5 opendap project update and demo
DESCRIPTION
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 PresentationTRANSCRIPT
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
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Client Library(libnc-dap)
DAP Protocol (via http)
Server(apache)
Handler(hdf4_handler)
Remote Data(HDF4)
View Data (User)
OPeNDAP Concept
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Visualization Tools
(gradsdap)
Typical Remote Access
FTP/HTTP
Visualization tools
(e.g. grads)
DAP Protocol (via http)
Server(apache)
Remote HDF5View Data (User)
OPeNDAP HDF5 Handler
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HDF5 Handler
Mapping HDF5 to DAP
• Compound Datatype
• Groups
• Object/Regional References
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Challenges
DAP Protocol (via http)
Server(apache)
View Data (User)
OPeNDAP HDF5 Handler with HDF-EOS5
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HDF5 Handler
Remote HDF5
Client Library(libnc-dap)
Visualization tools
(grads)
Remote HDF-EOS5
Challenges: 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
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Tweaks for HDF-EOS5 Added two default HDF5 handler
configuration options:• --enable-eos-grid
• --enable-eos-meta
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Challenges: OPeNDAP Clients
• Need special attributes on dataset.
• Need shared geolocation variables.
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Tweaks for OPeNDAP Clients
Added two optional handler configuration options:• --enable-short-name
• --enable-CF
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HDF5 Handler
DAP Protocol (via http)
Server(apache)
View Data (User)
OPeNDAP HDF5 Handler with HDF-EOS5
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HDF5 Handlerw/ CF options
Remote HDF5
Client Library(libnc-dap)
Visualization tools
(grads)
Remote HDF-EOS5
Day After Server Tweaks
• Finally, Happy Clients!
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Problems of Tweaking HDF5 Handler
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Remember that we added two optional HDF5 handler configuration options:
1.--enable-short-name
2.--enable-CFCauses ambiguity among
variable names (e.g. /GroupA/ozone vs.
/GroupB/ozone)
Drops some key attributes (e.g. StructMetdata, HDF_ROOT_GROUP)
HDF5-Friendly OPeNDAP Client Library
14HDF and HDF-EOS Workshop XII10/17/2008
DAP Protocol (via http)
Server(apache)
View Data (User)
HDF5 Handler
Client Library(libnc-dap)
Visualization tools
(grads)
Remote HDF5
HDF5 Handlerw/ CF options
HDF5-FriendlyClient Library(liboc-dap)
HDF5 GroupsView Groups???
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
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Example: Reference in HDF5
• Important for NPOESS
• Object / Regional Reference
• Map to DAP URL
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Example: dap2h5
• A test application for the client library
• It can construct HDF5 from DAP output
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DAP Protocol (via http)
Server(apache)
View Data (User)
HDF5-F. Client Library App.
(dap2h5)
Remote HDF5
HDF5 Handler
HDF5-FriendlyClient Library
(liboc-dap)
Group/Ref.View Group/Ref.
• One more reason:
Help Clients to view Swath
Our Client Library(prototype)
HDF5 Handler
DAP Protocol (via http)
Server(apache)
View Data (User)
Visualizing HDF-EOS5 Grids
19HDF and HDF-EOS Workshop XII10/17/2008
HDF5 Handlerw/ CF option
Remote HDF5
Client Library(libnc-dap)
Visualization tools
(grads)
Remote HDF-EOS5
Swath
Visualizing HDF-EOS5 Swath Problem
???
HDF5-FriendlyClient Library(liboc-dap)
Visualization Tools
(gradsoc)
View Swath
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
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
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Caution
• Our Client Library is ONLY A PROTOTYPE!
It does NOT support all DAP data types
It does NOT support all AURA files It does NOT support all Visualization clients
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Summary
• HDF5 Access via OPeNDAP Is Easy Is used by GES DISC to serve Aura
files
• HDF5-Friendly OPeNDAP Client Library Serves HDF5 better(EOS swath) Benefits visualization clients
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Future Work
• HDF5 to DAP2 Mapping Document
• Release HDF5-friendly OPeNDAP
Client Library (Prototype)
• URL: http://hdfgroup.org/projects/opendap
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Credits
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Acknowledgement
This work was supported basing upon the Cooperative Agreement with the National Aeronautics and Space Administration (NASA) under NASA grant NNX06AC83A, NNX08A077A 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.
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