Technical interoperability: Streaming protocols

Last updated on 2025-11-18 | Edit this page

Estimated time: 40 minutes

Overview

Questions

  • What is the DAP protocol?
  • Why is DAP an example of interoperability?
  • How to access a NetCDF file using OpenDAP interface, via DAP protocol?
  • How to read a NetCDF file programatically, using DAP protocol - with open_dataset from xarray Python library.
  • How to explore and manipulate a NetCDF file programatically.

Objectives

  • Understand why DAP is an interoperable protocol.
  • Know how to access and read a NetCDF file using DAP protocol.

Content

✔ Streaming protocols = Technical interoperability OPeNDAP / DAP allow:

SH 

• Access without downloading
• Server-side subsetting
• Efficient slicing for large NetCDF

✔ Why this matters • Enables scalable workflows (ERA5, ORAS5, CMIP6) • Facilitates AI training pipelines

Hands-on Exercise (Python) • Use Python client to read remote NetCDF via OPeNDAP • Perform a small selection (time window, variable subset) • Compare cost vs full file download

Challenge

Exercise: TRUE or FALSE?

Is this statement true or false? > The xarray.open_data() function you used, has downladed the dataset file to your computer. Whay do you think so?

No, the data has been accessed with the DAP protocol, which allows to explore and summarise the dimensions of the data, but they have not been downloaded to the computer.

Key Points
  • OPeNDAP (DAP) is a protocol that enables remote access to subsets of scientific datasets without downloading entire files, exemplifying technical interoperability.
  • Using OPeNDAP allows efficient server-side subsetting and slicing of large NetCDF files, facilitating scalable workflows for large climate datasets.
  • Programmatic access to NetCDF files via OPeNDAP can be achieved using libraries like xarray, enabling efficient data exploration and manipulation.