HDF5 OPeNDAP Project Update and Demo MuQun Yang and Hyo-Kyung Lee (The HDF Group) James Gallagher (OPeNDAP, Inc.) 1HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

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 XII, Aurora, CO10/17/2008

Example Usage OPeNDAP Client OPeNDAP HDF4 Server HDF4 Syntactic Structure of Data Semantic Meaning of Data Actual Content of Data OPeNDAP Visualization Client 3HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Why Important? HDF5: NASA EOS / NPOESS ACCESS! NASA’s MISSION : ACCESS! Our MISSION: Build a DAP-HDF5 Bridge 4HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

OPeNDAP HDF5 Server 1.Map HDF5 Datatypes into DAP Datatypes 2.Plus, tweaks for OPeNDAP Clients to access HDF-EOS5 Files Goal: Access HDF5 data via OPeNDAP 5HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Mapping HDF5 Datatypes to DAP Compound Datatype Support for Group Object/regional References 6HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Some OPeNDAP Clients Cannot handle long variable names. Need special attributes on dataset. Handle only DAP Grid datatype. Handle only well-formed attributes. Not all OPeNDAP clients are created equal! 7HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Tweaks for OPeNDAP Clients Two configuration options --enable-short-name --enable-CF 8HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

HDF EOS Grid with No Dimension data  Clients expect Grid with Dimension data Some Attributes stored in Extremely Long String(s) (e.g. StructMetada.0)  Clients expect well-structured attributes Not all HDF5 files are created for DAP! 9HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Tweaks for HDF-EOS Two more configuration options --enable-eos-grid --enable-eos-meta 10HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Day After Server Tweaks Finally, Happy Clients! 11HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Some Things Hard: HDF5 Opaque, Bitmap, Enum, Variable Length types Illegal: Reserved characters in DAP are used in Dataset/Group name in HDF5 (that OPeNDAP HDF5 server can’t serve) 12HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Goals 1st : Access HDF5 via OPeNDAP The OPeNDAP HDF5 handler was released on March, 2008 at OPeNDAP website 2nd: Construct HDF5 data from OPeNDAP Bonus: Help clients to better access EOS Swath data 13HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

HDF5-Friendly OPeNDAP client library 14HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Example: Group in HDF5 Traditional 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 XII, Aurora, CO10/17/2008

Example: Reference in HDF5 Object / Regional Reference Map to DAP URL Important for NPOESS 16HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Only ODC can display Swath properly. One more reason: Help Clients to view Swath HDF5-Friendly OPeNDAP Client Library Easy but Rigid OPeNDAP NC Client Library!  easy: same as netCDF C interface  rigid: follows netCDF model Our client library must be Easy but Flexible No Latitude and Longitude Courtesy of NASA 17HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

libnc-dap ??? liboc-dap NC-Friendly OPeNDAP Client Library libdap dapserver OPeNDAP NC Server GrADS NetCDFView NetCDF HDF5 Group/Ref/Swath OPeNDAP HDF5 Server View HDF5 GrADS View G/R/Swath HDF5-Friendly OPeNDAP Client Library 18HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Summary of Client Library Prototype Finished coding Tested with GrADS visualization client Documented Working on a demo DAP to HDF5 tool via the client library prototype May test with NCL 10/17/2008HDF and HDF-EOS Workshop XII, Aurora, CO19

Example: dap2h5 A test application for the client library It can construct HDF5 from DAP output 20HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Demo: MLS swath via GrADS GrADS is modified to use our 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 XII, Aurora, CO10/17/2008

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 XII, Aurora, CO10/17/2008

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 XII, Aurora, CO10/17/2008

Future Work HDF5 to DAP2 Mapping Document Release HDF5-friendly OPeNDAP Client Library Prototype URL: h ttp://hdfgroup.org/projects/opendap/index.html 24HDF and HDF-EOS Workshop XII, Aurora, CO10/17/2008

Credits Mike Folk (THG) 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 XII, Aurora, CO10/17/2008

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 XII, Aurora, CO10/17/2008