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Part III. Appendix 2: Data TransportAnnex B: Overview ofExisting SystemsMembers of the Data Transport Team are aware of several data systems that address one or more ofthe issues raised in the Introduction for Earth science data. A brief overview of these systems is presentedin this section in order to identify pieces of the systems that might be appropriate for adoptioninto the data transport component of IOOS.OPENDAP/NVODSThe data access protocol of the Open source Project for a Network Data Access Protocol(OPeNDAP) forms the core of the National Virtual Ocean Data System (NVODS). NVODS wasfunded by the National Oceanographic Partnership Program as a step “toward an integrated oceanobserving and prediction system (IOO&PS)” with the stated objective of “… develop[ing] conceptsthat maximize flexibility and utility of a hub-node system for the future.”The design of the OPeNDAP data access protocol (OPeNDAP, originally referred to as the DODSdata access protocol) was based on two fundamental criteria: (1) servers must be easy to install, and(2) the system must interface to existing application software. A system that satisfies this basic philosophywill allow individual data collectors as well as national archives to be data providers, and itwill allow researchers, operational modelers, interested hobbyists—everybody—to use familiar andappropriate software.The OPeNDAP approach is to use the standardized interfaces defined by multiple file APIs (e.g.,NETwork Common Data Format (NetCDF), HDF) as the point at which to insert the distributeddata infrastructure. In this approach, existing applications—both commercial applications andthose built within the science community—are “relinked” with new libraries that masquerade asthe original file I/O library. The applications are unaware that they have been extended to performnetwork access. The data from remote files are made available through servers that invert the process—usingthe standard file or database APIs to read the files and then provide the data over theInternet in a format-neutral representation. The virtues of this approach are adaptability, leveraging,and invisibility:1. The investment that each scientific project has made in its software tools is protected. Users continueto use the software tools with which they are already familiar—now extended to performremote data access.171