OPeNDAP - DAP-2 and DAP-4

OPeNDAP Data Access Protocols (DAP2 and DAP4)

The OPeNDAP Data Access Protocol (DAP) provides Web API-based access to remote scientific datasets over the web. The DAP and netCDF data models are very similar, both in terms of being composed of attributes and n-D array variables and in terms of their support for requesting subsets of the data. This similarity has lead to both the netCDF-C and netCDF-Java libraries supporting both DAP version 2 (DAP2) and DAP version 4 (DAP4). To avoid loss of information where the data models differ, various mappings are required. This document will describe the mappings used by the netCDF-C and netCDF-Java libraries.

For details on the DAP versions, see the DAP2 Specification (DOI) and the DAP4 Specification.

Accessing DAP Datasets in netCDF

To access a DAP dataset through one of the netCDF libraries, instead of the path and name of a local file, a DAP dataset is identified by an HTTPS (or HTTP) URL.