HDF5 OPeNDAP project update and demo

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Information about HDF5 OPeNDAP project update and demo
Technology

Published on February 17, 2014

Author: HDFEOS

Source: slideshare.net

Description

In this talk, we will give an update on the HDF5 OPeNDAP project. We will update the new features inside OPeNDAP HDF5 data handler. We will also introduce a new HDF5-Friendly OPeNDAP client library and demonstrate how it can help users to view and analyze remote HDF-EOS5 data served by OPeNDAP HDF5 handler. A demo will be presented with a customized OPeNDAP visualization client (GrADS) that uses the library.

HDF5 OPeNDAP Project Update and Demo MuQun Yang and Hyo-Kyung Lee (The HDF Group) James Gallagher (OPeNDAP, Inc.) 10/17/2008 HDF and HDF-EOS Workshop XII 1

OPeNDAP Review • A software framework that allows simple access to remote data • Data Access Protocol • Client-server model • Widely used by Earth Science Community 10/17/2008 HDF and HDF-EOS Workshop XII 2

OPeNDAP Concept Typical Remote Access View Data (User) FTP/HTTP Remote Data (HDF4) Visualization Tools tools (e.g. grads) (gradsdap) Handler (hdf4_handler) Client Library (libnc-dap) Server (apache) DAP Protocol (via http) 10/17/2008 HDF and HDF-EOS Workshop XII 3

OPeNDAP HDF5 Handler View Data (User) Remote HDF5 HDF5 Handler Server (apache) DAP Protocol (via http) 10/17/2008 HDF and HDF-EOS Workshop XII 4

Challenges Mapping HDF5 to DAP • Compound Datatype • Groups • Object/Regional References 10/17/2008 HDF and HDF-EOS Workshop XII 5

OPeNDAP HDF5 Handler with HDF-EOS5 View Data (User) Remote HDF-EOS5 HDF5 Visualization tools (grads) HDF5 Handler Client Library (libnc-dap) Server (apache) DAP Protocol (via http) 10/17/2008 HDF and HDF-EOS Workshop XII 6

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 10/17/2008 HDF and HDF-EOS Workshop XII 7

Tweaks for HDF-EOS5 Added two default HDF5 handler configuration options: • --enable-eos-grid • --enable-eos-meta 10/17/2008 HDF and HDF-EOS Workshop XII 8

Challenges: OPeNDAP Clients • Need special attributes on dataset. • Need shared geolocation variables. 10/17/2008 HDF and HDF-EOS Workshop XII 9

Tweaks for OPeNDAP Clients Added two optional handler configuration options: • --enable-short-name • --enable-CF 10/17/2008 HDF and HDF-EOS Workshop XII 10

OPeNDAP HDF5 Handler with HDF-EOS5 View Data (User) Remote HDF-EOS5 HDF5 Visualization tools (grads) HDF5 Handler w/ CF options Client Library (libnc-dap) Server (apache) DAP Protocol (via http) 10/17/2008 HDF and HDF-EOS Workshop XII 11

Day After Server Tweaks • Finally, Happy Clients! 10/17/2008 HDF and HDF-EOS Workshop XII 12

Problems of Tweaking HDF5 Handler Remember that we added two optional HDF5 handler configuration options: 1. --enable-short-name 2. --enable-CF Causes ambiguity among variable names (e.g. /GroupA/ozone vs. /GroupB/ozone) Drops some key attributes (e.g. StructMetdata, HDF_ROOT_GROUP) 10/17/2008 HDF and HDF-EOS Workshop XII 13

HDF5-Friendly OPeNDAP Client Library View??? Groups HDF5 Groups View Data (User) Remote HDF5 Visualization tools (grads) HDF5 Handler w/ CF options HDF5-Friendly Client Library (liboc-dap) (libnc-dap) Server (apache) DAP Protocol (via http) 10/17/2008 HDF and HDF-EOS Workshop XII 14

Traditional Groups Example:OPeNDAP clientin HDF5 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 10/17/2008 HDF and HDF-EOS Workshop XII 15

Example: Reference in HDF5 • Important for NPOESS • Object / Regional Reference • Map to DAP URL 10/17/2008 HDF and HDF-EOS Workshop XII 16

Example: dap2h5 View Group/Ref. Group/Ref. View Data (User) Remote HDF5 • HDF5-F. Client A test application for the client library Library construct HDF5 from DAP output HDF5 Handler • It canApp. (dap2h5) HDF5-Friendly Client Library (liboc-dap) Server (apache) DAP Protocol (via http) 10/17/2008 HDF and HDF-EOS Workshop XII 17

Our Client Library(prototype) • One more reason: Help Clients to view Swath

Visualizing HDF-EOS5 Swath Problem Visualizing HDF-EOS5 Grids View Swath ??? Swath View Data (User) Remote HDF-EOS5 HDF5 Visualization Tools tools (gradsoc) (grads) HDF5 Handler w/ CF option HDF5-Friendly Client Library (liboc-dap) (libnc-dap) Server (apache) DAP Protocol (via http) 10/17/2008 HDF and HDF-EOS Workshop XII 19

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 10/17/2008 HDF and HDF-EOS Workshop XII 21

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 10/17/2008 HDF and HDF-EOS Workshop XII 22

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 10/17/2008 HDF and HDF-EOS Workshop XII 23

Future Work • HDF5 to DAP2 Mapping Document • Release HDF5-friendly OPeNDAP Client Library (Prototype) • URL: http://hdfgroup.org/projects/opendap 10/17/2008 HDF and HDF-EOS Workshop XII 24

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) 10/17/2008 HDF and HDF-EOS Workshop XII 25

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. 10/17/2008 HDF and HDF-EOS Workshop XII 26

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