selection.md

selection

A selection is a dictionary-like object describing the ranges or sets coordinates, which point to multiple elements or sub-datacubes within a datacube.

For each key-value pair, the key may be any string and the values must be a list of values or ranges.

Examples

JSON

{
    "class": "operations",
    "stream": ["forecast"],
    "date": ["2024-01-01", "2024-01-03"],
    "parameter": ["t", "p", "q"],
    "step": {
        "start": 1,
        "end": 30,
        "step": 2
    }
}

• Ranges are specified as a dictionary specifying the start, end and (optionally) step.
• Lists of values are specified as a JSON list.
• Individual values can be specified just as in a identifier, or as a single-value list.
• It is also valid to use MARS-like syntax for ranges and lists:
  • "date": "20240101/to/20240103"
• A selection is indistinguishable from an identifier if all the values are simple individual values.

YAML

class: operations
stream: 
  - forecast
date:
  - 2024-01-01
  - 2024-01-03
parameter: [t, p, q]
step:
  start: 1
  end: 30
  step: 2

• All valid YAML formulations of the JSON specification are permitted.

MARS

class=operations,stream=forecast,date=20240101/to/20240103,parameter=t/p/q,step=1/to/30/by/2

• Ranges are specified as start/to/end, or optionally with a step as start/to/end/by/step.
• Lists of values are specified as item1/item2/item3
• Individual values can be specified just as in a identifier
• A selection is indistinguishable from a identifier if all the values are simple individual values.

URL Query

class=operations&stream=forecast&date=(2024-01-01,2024-01-03)&parameter=(t,p,q)&step=(from=1,to=30,step=2)