/ Specification

Getting Started

Introduction

An Example Workflow Executing Workflows Advanced Features

Core Concepts

Syntax

Type System

Primitive Types

Strings Files and Directories

Optional Types

Compound Types

Object Structs Enums

Hidden Types Type Conversion

Expressions

Declarations Operators Operator Precedence Member Access Ternary (if-then-else) Function Calls String Interpolation Placeholder Options Static Analysis

Documents

Versioning Import Statements

Tasks

Task Inputs Private Declarations Environment Variables Command Section Task Outputs Evaluation Requirements Hints Runtime Metadata Runtime Access

Workflows

Workflow Elements Evaluation Qualified Names Workflow Inputs Workflow Outputs Workflow Hints Call Statement Scatter Conditional

Standard Library

Numeric Functions

floor ceil round min max

String Functions

find matches sub

File Functions

basename join_paths glob size stdout stderr read_string read_int read_float read_boolean read_lines write_lines read_tsv write_tsv read_map write_map read_json write_json read_object read_objects write_object write_objects

String Array Functions

prefix suffix quote squote sep

Array Functions

range transpose cross zip unzip contains chunk flatten length select_first select_all

Map Functions

as_pairs as_map keys contains_key values collect_by_key

Enum Functions

value

Other Functions

defined length

Input/Output Formats

JSON Input Format JSON Output Format Extended Format JSON Serialization

Appendices

Appendix A: Serialization Appendix B: Namespaces Appendix C: Example Data

/

Home / Appendices

Appendices

Supplementary reference material for the specification

Supplementary information and reference materials for the WDL specification.

Appendix A: WDL Value Serialization and Deserialization

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© 2026 OpenWDL. Licensed under BSD 3-Clause.

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Getting Started

Introduction

An Example Workflow Executing Workflows Advanced Features

Core Concepts

Syntax

Type System

Primitive Types

Strings Files and Directories

Optional Types

Compound Types

Object Structs Enums

Hidden Types Type Conversion

Expressions

Declarations Operators Operator Precedence Member Access Ternary (if-then-else) Function Calls String Interpolation Placeholder Options Static Analysis

Documents

Versioning Import Statements

Tasks

Task Inputs Private Declarations Environment Variables Command Section Task Outputs Evaluation Requirements Hints Runtime Metadata Runtime Access

Workflows

Workflow Elements Evaluation Qualified Names Workflow Inputs Workflow Outputs Workflow Hints Call Statement Scatter Conditional

Standard Library

Numeric Functions

floor ceil round min max

String Functions

find matches sub

File Functions

basename join_paths glob size stdout stderr read_string read_int read_float read_boolean read_lines write_lines read_tsv write_tsv read_map write_map read_json write_json read_object read_objects write_object write_objects

String Array Functions

prefix suffix quote squote sep

Array Functions

range transpose cross zip unzip contains chunk flatten length select_first select_all

Map Functions

as_pairs as_map keys contains_key values collect_by_key

Enum Functions

value

Other Functions

defined length

Input/Output Formats

JSON Input Format JSON Output Format Extended Format JSON Serialization

Appendices

Appendix A: Serialization Appendix B: Namespaces Appendix C: Example Data