OPeNDAP (The Open-source Project for a Network Data Access Protocol) BOM Tutorial Introduction October 15, 2007 pfox@op

1. OPeNDAP(The Open-source Project for a Network Data Access Protocol) BOM Tutorial IntroductionOctober 15, 2007pfox@opendap.org BOM, Melbourne, VIC 20071015 (Fox)

2. Distributed Oceanographic Data System (DODS) • Conceived in 1993 at a workshop held at URI. • Objectives were: • to facilitate access to PI held data as well as data held in national archives and • to allow the data user to analyze data using the application package with which he or she is the most familiar. • Basic system designed and implemented in 1993-1995 by Gallagher and Flierl with NASA and NOAA funding. • From 1994 to present it has been extended with NASA, NOPP, NSF and NOAA funding. BOM, Melbourne, VIC 20071015 (Fox)

3. Some Definitions DAP = Data Access Protocol • Model used to describe the data; • Request syntax and semantics; and • Response syntax and semantics. OPeNDAP • The software; • Numerous reference implementations; • Core/libraries and services (servers and clients). OPeNDAP Inc. • OPeNDAP is a 501.c(3) non-profit corporation; • Formed to maintain, evolve and promote the discipline neutral DAP that was the DODS core infrastructure. BOM, Melbourne, VIC 20071015 (Fox)

4. Some Definitions Syntax • The computer representation of a data object - the data types and structures at the computer level; e.g., • T is a floating point array of 20 by 40 elements. Semantics • The information about the contents of an object; e.g., • T is sea surface temperature in degrees Celsius for a certain region of the Earth. BOM, Melbourne, VIC 20071015 (Fox)

5. Considerations with regard to the development of DAP and OPeNDAP • Many data formats • Many different client types Many data providers • Many different semantic representations of the data • Many different security requirements BOM, Melbourne, VIC 20071015 (Fox)

6. Broad Vision A world in which a single data access protocol is used for the exchange of data between network based applications regardless of discipline. A layer above TCP/IP providing for syntactic and semantic consistency not available in existing protocols such as FTP. BOM, Melbourne, VIC 20071015 (Fox)

7. Practical Considerations The broad vision: • Is syntactically achievable, but • Is not semantically achievable, at least not in the near term. BOM, Melbourne, VIC 20071015 (Fox)

8. OPeNDAP Inc. Mission Statement To maintain, evolve and promote a data access protocol (DAP) and reference implementation software (OPeNDAP) for the syntactically consistent exchange of data over the network. The DAP should provide syntactic interoperability across disciplines and allow for semantic interoperability within disciplines. BOM, Melbourne, VIC 20071015 (Fox)

9. OPeNDAP Inc. Vision Statement To achieve the mission: • OPeNDAP Inc. will be non-profit. • Easier to obtain federal funds. • The DAP is more likely to be adopted. • OPeNDAP software will be open source. • More likely to be adopted. • Need community contributions to software. • OPeNDAP Inc. will mix implementation with research. • Implementation - to encourage use. • Research - to keep the protocol current. BOM, Melbourne, VIC 20071015 (Fox)

10. OPeNDAP Inc. Vision Statement(cont) • OPeNDAP Inc. will rely primarily on federal funding. • Unlikely to obtain private funding for middleware. • Development to be use case driven. • Aligned with Vision/Mission. • Strategic direction will be sought from an Advisory Board consisting of data system experts and with input from you the community of developers. • OPeNDAP Inc. will seek partners. • OPeNDAP Inc. will utilize community working groups to develop ‘standards’ related to the DAP, OPeNDAP BOM, Melbourne, VIC 20071015 (Fox)

11. The Data Access Protocol (DAP) • The DAP has been designed to be as general as possible without being constrained to a particular discipline or world view. • The DAP is a discipline neutral data access protocol; it is being used in astronomy, medicine, earth science,… • Provides data format and location, and data organization transparency • Is metadata neutral BOM, Melbourne, VIC 20071015 (Fox)

12. DAP comparisons • File-based • GridFTP/FTP • HTTP • SRB • Service-based • Open-Geospatial Consortium, WCS, WMS, WFS, … • Virtual Observatory (Astronomy), SIAP, SSAP, STAP,… BOM, Melbourne, VIC 20071015 (Fox)

13. Limited interoperability Lightweight semantics Limited meaning, hard coded Limited extensibility The Astronomy approach; data-types as a service • VOTable • Simple Image Access Protocol • Simple Spectrum Access Protocol • Simple Time Access Protocol VO App2 VO App3 VO App1 OGC: {WFS, WCS, WMS} and SWE {SOS, SPS, SAS} use the same approach VO layer DBn DB2 DB3 … … … … DB1 BOM, Melbourne, VIC 20071015 (Fox)

14. Who is using DAP/ OPeNDAP? • Science examples • PMEL with their Tsunami inundation modeling • Ocean regional modelers to extract open boundary conditions • Visualization of data sets using MATLAB/IDL/… • Service examples • Live Access Server • Mapserver – OGC services and OPeNDAP data access (future) • Digital Library Service - metadata and catalogue info BOM, Melbourne, VIC 20071015 (Fox)

15. Data Access Protocol (DAP2) - Current • DAP2 currently a NASA/ESE ‘Standard’ • Current servers implement DAP2 DAP3 • DAP 2 + XML responses (implemented) BOM, Melbourne, VIC 20071015 (Fox)

16. DAP4 - Late 2007 (?) • DAP4 improvements over DAP3: • Additional datatypes • Swath • Blob - GIF, MPEG,… • Additional functionality • Check sum • Modulo • The additional datatypes will enable the DAP to be used in a wider variety of circumstances and are a direct response to users’ requests. BOM, Melbourne, VIC 20071015 (Fox)

17. What DAP means to me • Data access and transport • Response types: DAP objects versus file type • A DAP URL is essentially an HTTP URL with additional restrictions placed on the abs-path component. • DAP2-URL = "http://" host [ ":" port ] [ abs-path] • abs-path = server-path data-source-id [ "." ext[ "?" query ] ] • server-path = [ "/" token ] • data-source-id = [ "/" token ] • ext = "das" | "dds" | "dods" • The server-path is the pathname to the server, whereas data-source-id is the pathname to the data. BOM, Melbourne, VIC 20071015 (Fox)

18. OPeNDAP V3 Architecture Client Cgi style access Data • CGI-style access • Uses web server • HTTP protocol • Several request and response types • Reads data files, Databases, et c., returns info • May return DAP2 objects or other data • Client can be application, web browser or specialized server/service BOM, Melbourne, VIC 20071015 (Fox)

19. OPeNDAP V4 (Hyrax) Architecture Client OLFS BES Data • OPeNDAP Lightweight Front end Server (OLFS) • Receives requests and asks the BES to fill them • Uses Java Servlets • Does not directly ‘touch’ data • Multi-protocol • Back End Server (BES) • Reads data files, Databases, et c., returns info • May return DAP2 objects or other data • Does not require web server BOM, Melbourne, VIC 20071015 (Fox)

20. Binaries Generated There are approximately 80 binaries built on a nightly basis. They are built for the following platforms/operating systems: • Linux • FC4 • FC5 • MacOS-X (universal binaries when possible) • Windows XP, win32 • Java 1.5 (Tomcat 5.5) • IRIX (in four variants), Solaris, AIX, OSF BOM, Melbourne, VIC 20071015 (Fox)

21. Communication • Website (http://www.opendap.org and test.opendap.org) • SVN - Code repository (http://scm.opendap.org:8090/trac/browser/) • Trac - Task/milestone repository (http://scm.opendap.org:8090/trac/) • Telecons • Management - ~ Weekly • Developers - Weekly on Monday 11am MT • Twiki -> MediaWiki, for • Management • Developers • Coming soon http://docs.opendap.org (documentation on-line in MediaWiki form) • opendap-tech@opendap.org e-mail list • opendap@opendap.org for announcements (low vol.) BOM, Melbourne, VIC 20071015 (Fox)

22. Releases/Support • Periodic releases (announced on www.opendap.org and on email lists) • Support • OPeNDAP software (support@opendap.org) • opendap-tech@opendap.org discussions BOM, Melbourne, VIC 20071015 (Fox)

23. OPeNDAP and security • Both administrators and developers must consider security aspects of OPeNDAP software • First developer telecon each month addresses security • This will be addressed during this week BOM, Melbourne, VIC 20071015 (Fox)

24. OPeNDAP and authentication • ESG II/III • Australian Access Federation (AAF) • .htpasswd • Tomcat authentication BOM, Melbourne, VIC 20071015 (Fox)

25. ESG Security Services BOM, Melbourne, VIC 20071015 (Fox)

26. ESG Security Services - Client Interaction BOM, Melbourne, VIC 20071015 (Fox)

27. OPeNDAP Community Working Groups • Modeled after best practices of IETF, W3, OGC, IEEE, ISO, and others • Working Groups: • Authentication • Security • Server-side Functions • Virtualization (Aggregation) • Server-side processing • Geospatial Interoperability • Hyrax and *DS (TDS, GDS, FDS, etc.) • Semantics • DAPPER • netCDF C++ client • Response types • Metrics • Asynchronous transactions • DAP4 • Relational Database access via DAP • Wiki (http://docs.opendap.org/index.php/Working_Groups) BOM, Melbourne, VIC 20071015 (Fox)

28. OPeNDAP Community Working Groups • Terms of Reference http://docs.opendap.org/index.php/Terms_of_Reference • Abridged version: • Each OPeNDAP Working Group is established to apply members' expertise in their focus area to produce specific deliverables or outcomes • Types: Software and Documentation • Minimum 3 people • 6 month time-frame BOM, Melbourne, VIC 20071015 (Fox)

29. OPeNDAP System Elements The OPeNDAP data access protocol is used by a variety of system elements. • Clients • Browser Interfaces • Data System Integrators (ODC) • Servers • Processing Servers • Aggregating Servers - OPeNDAP chains • Ancillary Information Services BOM, Melbourne, VIC 20071015 (Fox)

30. Clients • Clients make requests and receive responses via the DAP. • Clients convert data from the OPeNDAP data model to the form required in the client application. BOM, Melbourne, VIC 20071015 (Fox)

31. IDL Client pyDAP pyDAP netCDF Java netCDF C ArcGIS ArcGIS Ferret GrADS IDV VisAD ncBrowse IDL Access Excel OPeNDAP Clients Internet NCL Client Matlab Client Web Browser OPeNDAP Data Connector NCL Matlab BOM, Melbourne, VIC 20071015 (Fox)

32. OCAPI • A pure OPeNDAP C API (OCAPI) for the client-side • Applications: • DAP-aware ‘commands’ for commercial analysis programs (e.g., IDL) • Scripting tools (e.g., Perl) BOM, Melbourne, VIC 20071015 (Fox)

33. OPeNDAP System Elements The OPeNDAP data access protocol is used by a variety of system elements. • Clients • Browser Interfaces • Data System Integrators (ODC) • Servers • Processing Servers • Aggregating Servers - OPeNDAP chains • Ancillary Information Services BOM, Melbourne, VIC 20071015 (Fox)

34. Browser interfaces BOM, Melbourne, VIC 20071015 (Fox)

35. OPenDAP Data Connector - a Data System Integrator GCMD GFDL netCDF URI HDF GSFC Binary Matlab NVODS OPeNDAP Access IDL ncBrowse IDV Ferret VisAD GrADS Excel ODC BOM, Melbourne, VIC 20071015 (Fox)

36. OPeNDAP System Elements The OPeNDAP data access protocol is used by a variety of system elements. • Clients • Browser Interfaces • Data System Integrators (ODC) • Servers • Processing Servers • Aggregating Servers - OPeNDAP chains • Ancillary Information Services BOM, Melbourne, VIC 20071015 (Fox)

37. Servers • Servers receive requests and provide responses via the DAP. • Servers convert the data from the form in which they are stored to the DAP. • Servers provide for subsetting of the data and more. BOM, Melbourne, VIC 20071015 (Fox)

38. netCDF DSP Tables Data Data Data Data General netCDF JGOFS DSP OPeNDAP Servers CDM Flat Binary ESML HDF4 HDF5 SQL FITS CDF CEDAR Data Data Data Data Data Data Data HDF5 FITS FreeForm HDF4 JDBC CDF CEDAR Internet BOM, Melbourne, VIC 20071015 (Fox)

39. ESG FDS GDS DAPPER CODAR pyDAP pyDAP Data Data Data Data Data Data Data netCDF OPeNDAP netCDF OPeNDAP GRIB BUFR OPeNDAP netCDF OPeNDAP CODAR General General TDS TDS Data Data netCDF OPeNDAP netCDF OPeNDAP OPeNDAP Servers (specialized processing) Internet BOM, Melbourne, VIC 20071015 (Fox)

40. Servers • Servers may also provide other services • Directory traversal. • Browser-based form to build URL. • Ascii or other representations of data. • Metadata associated with the data. • Server side functions. BOM, Melbourne, VIC 20071015 (Fox)

41. TDS JGOFS CODAR Data Data Data ESG FDS GDS DAPPER pyDAP netCDF OPeNDAP General CODAR Data Data Data Data Data netCDF OPeNDAP netCDF OPeNDAP GRIB BUFR OPeNDAP netCDF OPeNDAP General OPeNDAP Aggregation Servers Internet BOM, Melbourne, VIC 20071015 (Fox)

42. The Aggregation Server: An Example Local OPeNDAP HTML, GIF netCDF Data Set DSP Data Set File File File File File File DSP Aggregation Server Matlab Client Matlab BOM, Melbourne, VIC 20071015 (Fox)

43. OPeNDAP’s Hyrax (‘Server4’) • Uses a modular architecture to support different application-level protocols • Data access using DAP2 (DAP3) • Catalogs using THREDDS • Browsing using HTML and ASCII • Modules for data access • Different file types • Potential for database and scripting • Modules for commands • Commands provide varying operations for different protocols BOM, Melbourne, VIC 20071015 (Fox)

44. OPeNDAP V4 (Hyrax) Architecture Client OLFS BES Data • OPeNDAP Lightweight Front end Server (OLFS) • Receives requests and asks the BES to fill them • Uses Java Servlets • Does not directly ‘touch’ data • Multi-protocol • Back End Server (BES) • Reads data files, Databases, et c., returns info • May return DAP2 objects or other data • Does not require web server BOM, Melbourne, VIC 20071015 (Fox)

45. Info output HTML form ASCII output OPeNDAP Lightweight Front end Server GridFTP DAP2 Request Formulation** Request from client HTTP DAP2 DAP2 (GridFTP, HTTP) BES SOAP-DAP (HTTP) THREDDS Response to client BOM, Melbourne, VIC 20071015 (Fox)

46. BES BES Framework Network Protocol and Process start/stop activities PPT* Initialization/ Termination DAP2 Access Data Catalogs BES Commands/ XML Documents Commands** NetCDF3 HDF4 FreeForm Data Store Interfaces … *PPT is built in (other protocols) **Some commands are built in Data Data Data BOM, Melbourne, VIC 20071015 (Fox)

47. Additional material BOM, Melbourne, VIC 20071015 (Fox)

48. OPeNDAP relies on projects • To guide user-based requirements for application needs as well as OPeNDAP core development (use cases) • To provide maintenance and evolution of the core software and documentation • Currently: 7 active projects, covers next ~2-3 years, 2 pending proposals • …… BOM, Melbourne, VIC 20071015 (Fox)

49. Success What constitutes success of the OPeNDAP mission? Adoption of the DAP across a broad range of disciplines with extensive use in several of these. In order to achieve this the DAP must do the following: • It must be sufficiently flexible, all encompassing, etc. that it can be used across a broad range of data types. • Its implementation must be robust, secure, easy to use, provide for a broad range of services, etc. • The funding stream must be robust. • Active and engaged developer and user community BOM, Melbourne, VIC 20071015 (Fox)

50. Risks It is still the case that • Some other data access protocols are seen as more attractive regardless of whether or not they are, or • Other data access protocols are developed because their community is not aware of OPeNDAP or of what its capabilities are. • We will compare and contrast some of these today BOM, Melbourne, VIC 20071015 (Fox)