ESDS-RFC-017

Title

Mapping HDF5 to DAP2

Abstract

Data Access Protocol Version 2 (DAP2) and Hierarchical Data Format Version 5 (HDF5) are endorsed by NASA Headquarters as recommended Earth Science data systems standards. A significant number of HDF5 objects directly match DAP2 objects. However, because HDF5 and DAP2 have different data models, it can be difficult to fully map all HDF5 objects to DAP2 objects, yet several difficult-to-map HDF5 objects are essential for Earth Science applications. This technical note presents general HDF5-to-DAP2 mapping information, covering HDF5, datasets, groups, and attributes. Considerable detail is presented for the representation of those crucial, difficult-to-map objects that are required for Earth Science applications. This document also includes information about special HDF5-to-DAP2 mapping that enables easy access to NASA HDF-EOS5 data via DAP2 clients.

Synopsis

Final Recommendation

The ESDS-RFC-017 Technical Working Group (TWG) has conducted a review of ESDS-RFC-017 with the following conclusion:

That the Standards Process Group should forward ESDS-RFC-017 to NASA Headquarters with the recommendation that it be endorsed as a Technical Note.

Recommendation

Based on the responses received from reviewers and from additional research the TWG concludes that the “Mapping HDF5 to DAP2” RFC demonstrates sufficient operational readiness to be endorsed as a Technical Note by the SPG.  The TWG bases its recommendation on an analysis of the following factors in a NASA context.

Strengths – HDF5 and DAP2 are both endorsed Earth science data systems standards. Both are in widespread use within the NASA Earth science community. This document provides an excellent introduction to and solution to the problem of how to map objects of the two specifications to each other.

Weaknesses – No specific weaknesses were identified by the reviewers. However it was suggested that a valuable addition would be source code for a reference implementation of a program that implemented the mapping.

Applicability – This document very specifically addresses the mapping between two existing specifications. As such it clearly applies to those who are working with both. However, as an informational document it may also be of interest to users of just one of the two specifications or those interested in Earth science data and/or metadata.

Limitations – The document does not provide a comprehensive or complete mapping.

HIstory

ESDS-RFC-017 was processed in a two-stage review by the TWG. The TWG published the draft document and solicited reviews from the NASA Earth science community. The responses were all positive, but were accompanied by a number of comments that the authors decided should be addressed. The second version was published and the reviewers who had responded to the first version were contacted again. The subsequent reviews were again positive, with a few minor comments that were addressed by the authors in a third draft. This draft was reviewed by the TWG.