DAP3/4: Difference between revisions

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== DAP2 and DAP4 Specification efforts ==
== DAP2 and DAP4 Specification efforts ==


The DAP4 specification work has morphed into separate DAP2 and DAP4 specification efforts. The [http://www.opendap.org/pdf/ESE-RFC-004v1.1.pdf DAP 2.0 specification] ([http://www.esdswg.org/spg/rfc/ese-rfc-004 official version] with notes, et c.) was approved by NASA [http://www.esdswg.org/spg/ ESE/SPG] as a 'Community Standard' on 10/8/2007.  
The original (2004) DAP4 specification work morphed into separate DAP2 and DAP4 specification efforts. The [http://www.opendap.org/pdf/ESE-RFC-004v1.1.pdf DAP 2.0 specification] ([http://www.esdswg.org/spg/rfc/ese-rfc-004 official version] with notes, et c.) was approved by NASA [http://www.esdswg.org/spg/ ESE/SPG] as a 'Community Standard' on 10/8/2007.  


This page holds a collection of the DAP4 specification information
This page holds the DAP4 design and specification information


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Revision as of 20:43, 24 June 2008

DAP2 and DAP4 Specification efforts

The original (2004) DAP4 specification work morphed into separate DAP2 and DAP4 specification efforts. The DAP 2.0 specification (official version with notes, et c.) was approved by NASA ESE/SPG as a 'Community Standard' on 10/8/2007.

This page holds the DAP4 design and specification information


[DAPFourSpec DAP4 Specification Issues] A collection of DAP Data Model (mostly) issues

Editorial changes:

  • Need to conform to ESE RFC 003

If we're given the opportunity to think about DAP 2.1, I'd suggest:

2 Chunked encoding for data (so that we can have reliable error delivery in all cases) and 3 Eliminating the repetition of the array size for an array of Atomic types.

-- Main.JamesGallagher - 19 May 2004

Completed Changes From DAP2

OPeNDAP has three implementations of the DAP that it maintains: libdap (C++), Java-OPeNDAP (Java) and Ocapi (C; client-side only). There are other implementations which have been developed by other groups.

Features of DAP3/4 implemented in libdap

libdap is the reference implementation for DAP. Here are the DAP3 features implement in it so far:

  • DDX (although this implementation needs significant review and update)
  • XDAP header for the protocol version
  • Updated Version response which provides information about software versions and DAP version.

Proposed Changes To DAP2

Most desirable features

This is a list of the very most desirable features proposed for DAP3 (which when final will become DAP4). Only the very most important items are listed here, other documents list everything that's ever been suggested.

This ideas came directly from our experience with users of DAP 2 and from writing the DAP 2.0 specification:

  • Reliable error delivery when accessing data (known defect);
  • Eliminating the repetition of the array size for an array of Atomic types in the Data Response;
  • Support for 'any character in a name' using double quotes oe some other scheme;

These ideas are very general and are paired with there 'justification':

  • Use of Multi-part MIME for DataDDX (feature --> adherence to standard where applicable);
  • Develop the DataDDX (feature --> adherence to standard ...);
  • Ability to return checksums from data requests (feature with several use cases);