Metadata Sections

There are two optional sections that can be used to store metadata with the task: meta and parameter_meta. These sections are intended to contain metadata that is only of interest to human readers. The engine can ignore these sections with no loss of correctness. The extra information can be used, for example, to generate a user interface or documentation.

§Meta Values

The metadata sections can contain arbitrary key/value pairs. However, the values allowed in these sections ("meta values") are different than in other sections:

• Only string, numeric, and boolean primitives are allowed.
• Only array and object compound values are allowed.
• The special value null is allowed for undefined attributes.
• Expressions are not allowed.

A meta object is similar to a struct literal, except:

• A Struct type name is not required.
• Its values must conform to the same metadata rules defined above.

Note that, unlike the WDL Object type, metadata objects are not deprecated and will continue to be supported in future versions.

Example: test_meta_values.wdl

version 1.3

workflow test_meta_values {
  meta {
    authors: ["Jim", "Bob"]
    version: 1.1
    citation: {
      year: 2020,
      doi: "1234/10.1010"
    }
  }
}

{}

{}

§Task Metadata Section

This section contains task-level metadata. For example: author and contact email.

§Parameter Metadata Section

This section contains metadata specific to input and output parameters. Any key in this section must correspond to a task input or output.

Example: ex_paramter_meta_task.wdl

version 1.3

task ex_paramter_meta {
  input {
    File infile
    Boolean lines_only = false
    String? region
  }

  meta {
    description: "A task that counts the number of words/lines in a file"
  }

  parameter_meta {
    infile: {
      help: "Count the number of words/lines in this file"
    }
    lines_only: {
      help: "Count only lines"
    }
    region: {
      help: "Cloud region",
      suggestions: ["us-west", "us-east", "asia-pacific", "europe-central"]
    }
  }

  command <<<
    wc ~{if lines_only then '-l' else ''} < ~{infile}
  >>>

  output {
     Int result = read_int(stdout())
  }

  requirements {
    container: "ubuntu:latest"
  }
}

{
  "ex_paramter_meta.infile": "data/greetings.txt",
  "ex_paramter_meta.lines_only": true
}

{
  "ex_paramter_meta.result": 3
}