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title: Terminology
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<div class="terminology-page">
    <section class="terminology-hero">
        <div class="container" data-aos="fade-up">
            <div class="eyebrow">Scientific Workflow Systems</div>
            <h2>A Shared Terminology for Comparing Workflow Systems</h2>
            <p class="lead">A community-built framework that helps researchers describe workflow management systems in
                consistent terms. Use it to compare tools based on structure, composition, execution, data handling, and
                metadata practices instead of reputation or familiarity.</p>
            <div class="hero-actions">
                <a class="primary" href="https://arxiv.org/pdf/2506.07838" target="_blank">Read the research paper</a>
                <a href="/groups/terminology">Terminology working group</a>
            </div>
            <div class="hero-panels">
                <div class="hero-panel">
                    <h4>Purpose</h4>
                    <p>Provide a common vocabulary to describe and compare workflow management systems without ranking
                        them.</p>
                </div>
                <div class="hero-panel">
                    <h4>Audience</h4>
                    <p>Workflow system developers, domain scientists, and infrastructure teams evaluating WMS fit.</p>
                </div>
                <div class="hero-panel">
                    <h4>Outcome</h4>
                    <p>Clearer system selection, better design discussions, and more transparent reporting.</p>
                </div>
            </div>
            <div class="publication">
                <strong>Research Publication</strong><br />
                Suter, F., Coleman, T., Altintas, Í., Badia, R. M., Balis, B., Chard, K., Colonnelli, I., Deelman, E.,
                Tommaso, P. D., Fahringer, T., Goble, C., Jha, S., Katz, D. S., Köster, J., Leser, U., Mehta, K.,
                Oliver, H., Peterson, J.-L., Pizzi, G., Pottier, L., Sirvent, R., Suchyta, E., Thain, D., Wilkinson, S.
                R., Wozniak, J. M., Ferreira da Silva, R. (2025). <a href="https://arxiv.org/pdf/2506.07838"
                    target="_blank">A Terminology for Scientific Workflow Systems</a>. Future Generation Computer
                Systems.
            </div>
        </div>
    </section>

    <section class="terminology-section">
        <div class="container" data-aos="fade-up">
            <h3 class="section-title">How to use the terminology</h3>
            <p class="section-lead">Use the axes below as a checklist when documenting a system or comparing candidates
                for a new project.</p>
            <div class="usage-steps">
                <div class="usage-step">
                    <h4>1. Describe the workflow shape</h4>
                    <p>Clarify how tasks, data, and dependencies are organized and whether the workflow can adapt at
                        runtime.</p>
                </div>
                <div class="usage-step">
                    <h4>2. Capture how it is expressed</h4>
                    <p>Note whether users define workflows via schema files, APIs, or GUIs and how much detail is
                        required.</p>
                </div>
                <div class="usage-step">
                    <h4>3. Document execution + data behavior</h4>
                    <p>Summarize planning, orchestration, data movement, storage, and metadata capabilities.</p>
                </div>
            </div>
        </div>
    </section>

    <section class="terminology-section">
        <div class="container" data-aos="fade-up">
            <h3 class="section-title">Five axes of comparison</h3>
            <p class="section-lead">Each axis captures a core aspect of how a workflow system is designed and operates.
                Select the section you need and jump directly to the details.</p>
            <div class="toc-grid">
                <a class="toc-card" href="#workflow-characteristics">
                    <h4>Workflow Characteristics</h4>
                    <p>Structure, coupling, and adaptability.</p>
                </a>
                <a class="toc-card" href="#composition">
                    <h4>Composition</h4>
                    <p>How workflows are described and modularized.</p>
                </a>
                <a class="toc-card" href="#orchestration">
                    <h4>Orchestration</h4>
                    <p>Planning, execution models, and coordination.</p>
                </a>
                <a class="toc-card" href="#data-management">
                    <h4>Data Management</h4>
                    <p>Movement, storage, and data handling granularity.</p>
                </a>
                <a class="toc-card" href="#metadata-capture">
                    <h4>Metadata Capture</h4>
                    <p>Provenance, monitoring, and anomaly insight.</p>
                </a>
            </div>
        </div>
    </section>

    <section class="terminology-section" id="workflow-characteristics">
        <div class="container" data-aos="fade-up">
            <div class="axis">
                <div class="axis-header">
                    <div>
                        <h3>Workflow Characteristics</h3>
                        <p class="section-lead">Fundamental structural aspects that shape how workflows run and adapt.
                            These characteristics influence scheduling, optimization, and resource efficiency.</p>
                    </div>
                    <img src="/images/terminology/workflow_characteristics.svg" alt="Workflow characteristics axis" />
                </div>
                <div class="term-grid">
                    <div class="term-card">
                        <h4>Flow</h4>
                        <ul>
                            <li><span>Task:</span> Components receive inputs, produce outputs, and terminate; WMSs manage
                                execution order and dependencies.</li>
                            <li><span>Iterative:</span> Tasks run multiple times, ending after each iteration and waiting
                                to be invoked again.</li>
                            <li><span>Data:</span> Execution is driven by data movement; operators remain active while
                                data is available.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Granularity</h4>
                        <ul>
                            <li><span>Functions:</span> Workflows compose function calls; scripts and runtimes can be
                                viewed as workflows.</li>
                            <li><span>Standalone executables:</span> A common model where executables aggregate function
                                calls and process inputs to produce outputs.</li>
                            <li><span>Sub-workflows:</span> Hierarchical compositions break large workflows into reusable
                                modules.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Coupling</h4>
                        <ul>
                            <li><span>Tight:</span> Tasks must run concurrently, often co-located or synchronized via
                                periodic data exchange.</li>
                            <li><span>Loose:</span> No concurrency constraints, enabling flexible scheduling.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Dynamicity</h4>
                        <ul>
                            <li><span>Branches:</span> Conditional paths activate based on data, resource state, or
                                events.</li>
                            <li><span>Runtime interventions:</span> Users or external processes can modify execution
                                plans during runtime.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Domain</h4>
                        <ul>
                            <li><span>Specific:</span> Systems tuned for a single scientific community or discipline.</li>
                            <li><span>Agnostic:</span> Systems designed to serve multiple domains.</li>
                        </ul>
                    </div>
                </div>
            </div>
        </div>
    </section>

    <section class="terminology-section" id="composition">
        <div class="container" data-aos="fade-up">
            <div class="axis">
                <div class="axis-header">
                    <div>
                        <h3>Composition</h3>
                        <p class="section-lead">How workflows are defined, organized, and configured. This axis highlights
                            the tradeoff between expressiveness, abstraction, and accessibility.</p>
                    </div>
                    <img src="/images/terminology/composition.svg" alt="Composition axis" />
                </div>
                <div class="term-grid">
                    <div class="term-card">
                        <h4>Description Method</h4>
                        <ul>
                            <li><span>Schema:</span> Workflows described in files using specific formats (XML, JSON,
                                YAML, or a domain-specific language).
                                <ul>
                                    <li><span>Ad-hoc:</span> Syntax understood only by a single WMS.</li>
                                    <li><span>Standard:</span> Syntax aligned with shared standards such as CWL, IWIR, or
                                        WfFormat.</li>
                                </ul>
                            </li>
                            <li><span>API:</span> Workflow descriptions built in code using languages or templating
                                engines, enabling loops and conditionals.</li>
                            <li><span>GUI:</span> Workflow authoring through a graphical interface.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Level of Abstraction</h4>
                        <ul>
                            <li><span>Abstract:</span> Logical structure and resource needs only; no infrastructure
                                bindings.</li>
                            <li><span>Intermediate:</span> Mix of high-level structure with required execution details.</li>
                            <li><span>Concrete:</span> Fully specified workflow ready to run as described.</li>
                            <li><span>Implicit:</span> Structure inferred from API calls or dataset metadata.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Modularity</h4>
                        <ul>
                            <li><span>Flat:</span> Single-layer description of components.</li>
                            <li><span>Hierarchical:</span> Nested sub-workflows support scalable design and reuse.</li>
                        </ul>
                    </div>
                </div>
            </div>
        </div>
    </section>

    <section class="terminology-section" id="orchestration">
        <div class="container" data-aos="fade-up">
            <div class="axis">
                <div class="axis-header">
                    <div>
                        <h3>Orchestration</h3>
                        <p class="section-lead">Execution management approaches, from planning to the way tasks are
                            launched and coordinated across resources.</p>
                    </div>
                    <img src="/images/terminology/orchestration.svg" alt="Orchestration axis" />
                </div>
                <div class="term-grid">
                    <div class="term-card">
                        <h4>Planning</h4>
                        <ul>
                            <li><span>Static:</span> All scheduling decisions are made before execution starts.</li>
                            <li><span>Dynamic:</span> Scheduling adapts during execution based on runtime information.</li>
                            <li><span>Event-driven:</span> Execution reacts to triggers and conditions at runtime without
                                pre-planning the entire workflow.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Execution</h4>
                        <ul>
                            <li><span>Runner:</span> WMS acquires resources and manages task execution directly.</li>
                            <li><span>Resource Manager:</span> Resource allocation is delegated to schedulers or container
                                orchestration systems.</li>
                            <li><span>Serverless:</span> Execution is delegated to cloud services that manage scaling and
                                infrastructure.</li>
                        </ul>
                    </div>
                </div>
            </div>
        </div>
    </section>

    <section class="terminology-section" id="data-management">
        <div class="container" data-aos="fade-up">
            <div class="axis">
                <div class="axis-header">
                    <div>
                        <h3>Data Management</h3>
                        <p class="section-lead">How data moves through a workflow, how it is stored, and the granularity
                            of data exchange between components.</p>
                    </div>
                    <img src="/images/terminology/data_management.svg" alt="Data management axis" />
                </div>
                <div class="term-grid">
                    <div class="term-card">
                        <h4>Granularity</h4>
                        <ul>
                            <li><span>Batch:</span> Inputs are consumed and outputs produced in full at task boundaries.</li>
                            <li><span>Pipelined:</span> Components stream records as they run, common in in situ analysis.</li>
                            <li><span>Partitioned:</span> Data is divided into partitions for transfer and processing.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Transport</h4>
                        <ul>
                            <li><span>File-based:</span> Intermediate data is written to and read from files.</li>
                            <li><span>Streaming:</span> Data is pushed directly between components.
                                <ul>
                                    <li><span>In-memory:</span> Shared memory transfer for co-located components.</li>
                                    <li><span>Network:</span> Data streams across networked nodes.</li>
                                </ul>
                            </li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Storage</h4>
                        <ul>
                            <li><span>File System:</span>
                                <ul>
                                    <li><span>Local:</span> Data stored on node-local storage.</li>
                                    <li><span>Shared:</span> Centralized storage accessible across a cluster.</li>
                                </ul>
                            </li>
                            <li><span>Distributed:</span> Storage spread across multiple facilities for scalability and
                                resilience.</li>
                            <li><span>Replicated:</span> Redundant copies improve reliability and availability.</li>
                        </ul>
                    </div>
                </div>
            </div>
        </div>
    </section>

    <section class="terminology-section" id="metadata-capture">
        <div class="container" data-aos="fade-up">
            <div class="axis">
                <div class="axis-header">
                    <div>
                        <h3>Metadata Capture</h3>
                        <p class="section-lead">Context captured during execution that supports reproducibility,
                            optimization, monitoring, and error handling.</p>
                    </div>
                    <img src="/images/terminology/metadata_capture.svg" alt="Metadata capture axis" />
                </div>
                <div class="term-grid">
                    <div class="term-card">
                        <h4>Provenance</h4>
                        <ul>
                            <li><span>Prospective:</span> Captures workflow design, configuration, and intended behavior.</li>
                            <li><span>Retrospective:</span> Captures what happened during execution, including lineage and
                                runtime data.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Monitoring</h4>
                        <ul>
                            <li><span>Performance insights:</span> Tracks resource use and bottlenecks during execution.</li>
                            <li><span>Optimization input:</span> Data supports rescheduling and future workflow tuning.</li>
                        </ul>
                    </div>
                    <div class="term-card">
                        <h4>Anomaly Detection</h4>
                        <ul>
                            <li><span>Fault handling:</span> From logging warnings to retrying tasks or triggering
                                fallback branches.</li>
                            <li><span>User intervention:</span> Supports escalation when automation cannot resolve the
                                issue.</li>
                        </ul>
                    </div>
                </div>
            </div>
        </div>
    </section>
</div>