DAW Model

N-WAVE can write a workflow as a DAW model: a description of it in terms that don't belong to Nextflow or to N-WAVE, and read one back. It follows the consolidated metamodel of data analysis workflow (DAW) languages by Hilbrich et al. (2022, metamodel and mappings), which describes workflows of Nextflow, Airflow, CWL, Argo and others with the same few concepts:

• a DAW solves a problem, and can be divided into sub-DAWs;
• a Task is a solution of a (sub-)problem;
• a Storage is where data comes from or goes to;
• an Interconnection passes data (or control) between them.

Use it to share a workflow with tools that aren't Nextflow, to compare workflows, or to start from a workflow that was only sketched: its steps open as placeholders to fill in.

Export and import

• Export in the bottom bar → Download DAW model downloads <workflow>.daw.json.
• Import Workflow on the home page takes a DAW model like a Nextflow script: choose the file, or paste it.

A model N-WAVE wrote gives the same canvas back (nodes, settings, connections, positions, groups, notes), and exporting that gives the same file. It contains the files uploaded to File Input nodes and the samplesheets. It leaves out run profiles, which name clusters and accounts.

What becomes what

N-WAVE follows the metamodel's own mapping of Nextflow where it has one.

On the canvas	In the model
The workflow	DAW
A group of steps	sub-DAW with its Tasks
An nf-core subworkflow, a pipeline, a custom workflow node	sub-DAW by reference (its parts aren't listed)
A process: nf-core module, custom node, Filter, Map, Merge	Task: Executable, with its code or the nf-core module it refers to
A step without an implementation yet	Task: Task (the solution idea only)
Channel code	Task: InlineDescription
Channel code that decides which steps get data (if, branch, filter)	Task: SkipTask
Code for when the run completes or fails	Task: Monitor
File Input, Samplesheet, Display Output	Storage: FileStorage
Parameters	Storage: IntermediateStorage (FileStorage when all are files)
A connection	StreamingInterconnection (a channel), or SimpleSendDataInterconnection from a single value
A step's container and process settings (ext.args, …)	ExecutionContext of its Task

A model from elsewhere

A model without N-WAVE's own data, written by another tool or by hand, opens as a skeleton:

In the model	On the canvas
A Task with Nextflow process code	a step that keeps the code
A Task that refers to an nf-core module	the nf-core node
InlineDescription, SkipTask or Monitor with Nextflow code	channel code
Any other Task, and a sub-DAW given by reference only	a placeholder step
A sub-DAW with its parts	its steps, as a group
A Storage with values	Parameters
A Storage data comes from / goes to	File Input / Display Output

A placeholder has the task's name, description, inputs and outputs, and a script that only says it has no implementation yet. The workflow check lists each one, so the workflow doesn't run until they are written (in the node's Code tab) or replaced with nodes from the library. Exported again, a placeholder is a Task without an implementation, as it came.

A minimal model:

{
  "schema": "n-wave-daw/1",
  "daw": {
    "id": "average",
    "name": "Average of values",
    "tasks": [
      { "id": "sum", "name": "Sum", "type": "Task", "description": "Add up the values." },
      { "id": "count", "name": "Count", "type": "Task" }
    ],
    "storages": [{ "id": "input", "name": "Values", "type": "FileStorage" }],
    "interconnections": [
      { "id": "i1", "type": "StreamingInterconnection", "from": { "element": "input" }, "to": { "element": "sum" } },
      { "id": "i2", "type": "StreamingInterconnection", "from": { "element": "input" }, "to": { "element": "count" } }
    ]
  }
}

The file format

The metamodel is a class diagram and has no file format of its own, so the JSON is N-WAVE's form of it ("schema": "n-wave-daw/1"), with a JSON Schema for other tools. Each element's type is a class of the metamodel. Two things go beyond it:

• Ports. The metamodel connects elements; N-WAVE also needs to know which output goes to which input, so the ends of an interconnection can name a port.
• nwave. What has no class in the metamodel, and what N-WAVE needs to give its own canvas back exactly: each node's settings and position, notes, and the workflow's run settings. Other tools can ignore it and leave it out.

See also

• Importing workflows and Exporting projects: the same for Nextflow code
• Building workflows