1 / 23

Open Data Access Protocol

Open Data Access Protocol. Webb Pinner May 2, 2005 CSC 536. Acknowledgements. Peter Cornillan - Graduate School of Oceanography, DODS James Gallager - OpenDAP.org Tom Sgouros - OpenDAP.org John Howland - Deep Submergence Lab, Woods Hole Oceanographic Institute. Outline of Presentation.

geri
Download Presentation

Open Data Access Protocol

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Open Data Access Protocol Webb Pinner May 2, 2005 CSC 536

  2. Acknowledgements Peter Cornillan - Graduate School of Oceanography, DODS James Gallager - OpenDAP.org Tom Sgouros - OpenDAP.org John Howland - Deep Submergence Lab, Woods Hole Oceanographic Institute

  3. Outline of Presentation Background Information The OpenDAP protocol Oceanographic Dive Reply System Summary Questions?

  4. Background • DODS was created in 1993 by URI, GSO, MIT, NASA and NOAA for use in oceanographic datasets. • It's purpose was to "define the structure of a client-server based distribution system for access to oceanographic data over the Internet”

  5. Background (cont.) • DODS was quickly adapted for use by the atmospheric data community. • Because DODS no longer dealt with strictly with ocean data the name was changed to the Data Access Protocol • 2002 the project was made open source and thus OpenDAP was created

  6. The OpenDAP Architecture • Provides uniform interface to data • Allows SQL-like data querying • Read-only access to data • Platform independent • Client/server model • For use over Internet (TCP/IP)

  7. OpenDAP Implementation • Uses http as transport protocol • Server implemented as CGI extension in Apache webserver • Requests for data are sent to server in the form of a URL • URL sent to server describes exactly what data is requested • Includes which columns and/or data constraints.

  8. Example URL • http://dap_server/cgi-bin/nph-dods/data/dataset1 • http - protocol • dap_server - servername • cgi-bin/nph-dods - dap server software location • data - director where dataset is located • dataset1 - name of dataset • Extension determines which service is called • Constraints may be added to request specific datasets

  9. OpenDAP Implementation(Services) • Three basic services: • Data Descriptor Service (DDS) • Data Attribute Service (DAS) • Data (DODS) • Additional services: • HTML form (HTML) • ASCII representation (ASCII)

  10. OpenDAP Implementation(Constraints) • Constraints specify which fields to display and in what order to display them. • http://…/data.dods?date&time&temp • Constraints specify search criteria. • http://…/data.dods?temp>100&temp<175

  11. Current Users • NASA - Global Hydrology Resource Center • NOAA - National Data Buoy Center (NDBC) • NOAA - National Oceanographic Data Center (NODC) • University of Hawaii/SOEST - Sea Level Center (SLC) • Woods Hole - Upper Ocean Mooring Data Archive (UOP)

  12. OpenDAP DEMO

  13. OpenDAP = Middleware/Dist. System? • Kinda, sorta, not quite • Uniform interface to data (Middleware) • User is unaware of OS, storage format or access protocol (Middleware) • Data distributed across multiple servers (Dist. System)

  14. OpenDAP = Middleware/Dist. System? • Read-only Access • Each Dataset is independent of other datasets • No such thing as replication, commit protocols, concurrency control, etc.

  15. Oceanographic Dive Replay System

  16. Oceanographic Dive Replay System • Replay a dive complete with textual data and images • Retrieve data from remote servers • Provide a graphical means to interact with large ascii datasets • Provide means to search dataset

  17. WHOI - Virtual Vans

  18. WHOI - Virtual Vans • Replays a dive complete with textual data and images • Retrieves data from WHOI server • Provide a HTML based GUI • Provide means to search event data

  19. Virtual Vans - Shortcomings • Unable to search by any other dataset • Unable to create custom datasets for downloading • GUI can not dynamically accommodate new sensors. • All datasets stored at one location

  20. OpenDAP Replay System • Use DAS, DDS information to dynamically generate interface • Use URL constraints to search based on any data type • Use URL constraints to customize downloaded datasets • Multiple servers may provide datasets

  21. OpenDAP Replay System

  22. Summary • Introduced the OpenDAP protocol, it’s history, architecture and current uses • Quick OpenDAP demo • Case Study: Dive Replay System • Looked at existing system and its faults • Discussed a new OpenDAP-based systsm and its advantages

  23. Questions?

More Related