APAC, Perth, WA OPeNDAP (The Open-source Project for a Network Data Access Protocol) APAC Tutorial October 12, 2007

APAC, Perth, WA 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. 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.

APAC, Perth, WA 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.

APAC, Perth, WA 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 by Gallagher and Flierl with NASA and NOAA funding.  From 1994 to present it has been extended with NASA, NOPP, NSF and NOAA funding.

APAC, Perth, WA Considerations with regard to the development of OPeNDAP  Many data providers  Many data formats  Many different semantic representations of the data  Many different security requirements  Many different client types

APAC, Perth, WA 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.

APAC, Perth, WA Practical Practical Considerations The broad vision:  Is syntactically achievable, but  Is not semantically achievable, at least not in the near term.

APAC, Perth, WA OPeNDAP Mission Statement To maintain, evolve and promote a data access protocol (DAP) 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 *****.

APAC, Perth, WA OPeNDAP Vision Statement To achieve the mission:  OPeNDAP 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 will mix implementation with research.  Implementation - to encourage use.  Research - to keep the protocol current.

APAC, Perth, WA OPeNDAP Vision Statement (cont)  OPeNDAP 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 will seek partners.  OPeNDAP will utilize community working groups to develop ‘standards’ related to the DAP, OPeNDAP

APAC, Perth, WA OPeNDAP tactics The fundamental objective of OPeNDAP and OPeNDAP Inc. is to facilitate internet access to scientific data This is done by: –Providing a protocol (DAP) to access data over the internet, –Hiding the format (and organization) in which the data are stored from the user, and –Providing subsetting (and other) capabilities for the data at the server OPeNDAP is based on a multi-tier architecture OPeNDAP software is open source Working groups formed on specific topics

APAC, Perth, WA 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 ……

APAC, Perth, WA 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

APAC, Perth, WA 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

APAC, Perth, WA To Succeed OPeNDAP must make sure that:  It’s (server and client) capabilities are well known across a broad range of disciplines.  The data model is inclusive.  The implementation is robust and meets user’s needs.  The DAP coexists with other protocols.  It has a robust funding base.  It has extensive documentation.

APAC, Perth, WA Robust Funding? What is an appropriate level of activity (funding) for OPeNDAP? What should OPeNDAP be doing?  Core only? + Clients and servers? + Demonstration projects? Should OPeNDAP be a small staff (core only) or…? What priority should be assigned to the elements currently being developed? Which of these go beyond the core?  DAP4  AIS - metadata consistency  THREDDS - Catalogs  Toolkits - Matlab, IDL,…  Grid capabilities  OTHERS?

APAC, Perth, WA Releases/Support  Periodic releases  User services - OPeNDAP  User support - first line of defense  Manages the opendap-dev discussions

APAC, Perth, WA 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

APAC, Perth, WA Communication  Website ( and test.opendap.org)  SVN - Code repository (  Trac - Task/milestone repository (  Telecons  Management - Weekly  Developers - Weekly on Monday 11am MT  Twiki -> MediaWiki  Management  Developers  Coming soon  opendap-dev list - main mechanism for messages

APAC, Perth, WA OPeNDAP Community Working Groups  Modeled after best practices of IETF, W3, OGC, IEEE, ISO, and others  Working Groups:  Authentication Authentication  Security Security  Server-side Functions 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 (

APAC, Perth, WA OPeNDAP Community Working Groups  Terms of Reference (abridged)  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

APAC, Perth, WA  Servers  Processing Servers  Aggregating Servers - OPeNDAP chains  Clients  Ancillary Information Services  Browser Interfaces  Data System Integrators (ODC) The OPeNDAP data access protocol is used by a variety of system elements. OPeNDAP System Elements

APAC, Perth, WA Servers  Servers receive requests and provide responses via the DAP.  Servers convert the data from the form in which they are stored to the OPeNDAP data model.  Servers provide for subsetting of the data and more.

APAC, Perth, WA Data HDF5 HDF4JDBC FreeFormFITS CDFCEDAR Data netCDF HDF4HDF5 Data DSP Data JGOFS TablesSQLFITSCDF Flat Binary CEDAR Data General ESML OPeNDAP Servers

APAC, Perth, WA Data GRIB BUFR OPeNDAP GDS Data CODAR Data FDS netCDF OPeNDAP Data General pyDAP Data DAPPER netCDF OPeNDAP Data netCDF OPeNDAP TDS Data General pyDAP Data netCDF OPeNDAP TDS OPeNDAP Servers (specialized) Data ESG netCDF OPeNDAP

APAC, Perth, WA Servers  Servers may also provide other services  Directory traversal.  Browser-based form to build URL.  ASCII version of data. ASCII version of data.  Metadata associated with the data.  Server side functions.

APAC, Perth, WA Data General pyDAP OPeNDAP Aggregation Servers Data GRIB BUFR OPeNDAP GDS Data CODAR Data FDS netCDF OPeNDAP Data DAPPER netCDF OPeNDAP Data TDS netCDF OPeNDAP Data General JGOFS Data ESG netCDF OPeNDAP

APAC, Perth, WA The Aggregation Server: An ExampleAggregationServer File DSP Data Set File netCDF Data Set File Matlab Local OPeNDAP HTML, GIF Matlab Client DSP

APAC, Perth, WA  Servers  Processing Servers  Aggregating Servers - OPeNDAP chains  Clients  Ancillary Information Services  Browser Interfaces  Data System Integrators (ODC) The OPeNDAP data access protocol is used by a variety of system elements. OPeNDAP System Elements

APAC, Perth, WA 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.

APAC, Perth, WA netCDF C FerretGrADS netCDF Java IDVVisADncBrowse Matlab Client Access Excel IDL Client ArcGIS pyDAP OPeNDAP Clients ArcGIS pyDAP NCL Client

APAC, Perth, WA  Servers  Processing Servers  Aggregating Servers - OPeNDAP chains  Clients  Ancillary Information Services  Browser Interfaces  Data System Integrators (ODC) The OPeNDAP data access protocol is used by a variety of system elements. OPeNDAP System Elements

APAC, Perth, WA Ancillary Information Service Current capability: Attributes only Client-side only Local and remote resources Local resource databases The AIS enables users to augment the metadata for a data source in a controlled way without requiring write access to the original data. By using the DAP, users are also isolated from data format issues.

APAC, Perth, WA AIS enhancements Remote resource databases AIS server AIS for variables These enhancements will greatly expand the usefulness of the AIS: Remote resource databases and an AIS server will enable third-party ‘AIS sites’ which may be sponsored by project offices or institutions, et cetera. AIS for variables will enable adding metadata which are stored as ‘data.’

APAC, Perth, WA Proposed AIS Server Client linked w/DAP Software Data Source AIS Server AIS Resource Client requests metadata from the AIS server (which appears no different from any other DAP server). 1. The AIS server gets metadata from data source 2. The AIS server gets matching the AIS resource using the AIS database and merges it into the metadata. 3. The AIS server returns resulting the metadata object.

APAC, Perth, WA  Servers  Processing Servers  Aggregating Servers - OPeNDAP chains  Clients  Ancillary Information Services  Browser Interfaces  Data System Integrators (ODC) The OPeNDAP data access protocol is used by a variety of system elements. OPeNDAP System Elements

APAC, Perth, WA 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)

APAC, Perth, WA ODCIDL GrADS Ferret IDV VisAD ncBrowse Matlab Excel Access OPeNDAP GFDL netCDF GSFC Binary URI HDF GCMD ODC NVOD S - a Data System Integrator

APAC, Perth, WA  The DAP has been designed to be as general as possible without being constrained to a particular discipline or world view. The Data Access Protocol (DAP)  The DAP is a discipline neutral data access protocol; it is being used in astronomy, medicine, earth science,…

APAC, Perth, WA Data Access Protocol (DAP2) - Current  DAP2 currently a NASA/ESE ‘Standard’  Current server (OPeNDAP 3.x; aka SERVER3)  XML responses (implemented) DAP3

APAC, Perth, WA 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.

APAC, Perth, WA OPeNDAP’s Hyrax (‘Server4’) Uses a modular architecture to support different application-level protocols –Data access using DAP –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

APAC, Perth, WA Hyrax Architecture OLFSBES  OPeNDAP Lightweight Front end Server (OLFS)  Receives requests and asks the BES to fill them  Uses Java Servlets  Does not directly ‘touch’ data Data  Back End Server (BES)  Reads data files, Databases, et c., returns info  May return DAP objects or other data

APAC, Perth, WA GridFTP DAP2 GridFTP DAP2 HTTP DAP2 HTTP DAP2 ASCII output HTML output Info output OPeNDAP Lightweight Front end Server THREDDS Request Formulation** Request from client Response to client BES SOAP-DAP DAP2

APAC, Perth, WA BES Network Protocol and Process start/stop activities Data Store Interfaces BES Framework PPT* Initialization/ Termination DAP2 Access NetCDF3HDF4FreeForm … Data Catalogs Commands** BES Commands/ XML Documents *PPT is built in (other protocols) **Some commands are built in

APAC, Perth, WA Today’s Overview DAP Servers and Services DAP Clients and Services