Use Case

Core meaning

A **use case** is a structured description of how a user, role, or external system interacts with a system to achieve a specific goal in a defined context. It typically captures:

– The actor (person, role, or external system) initiating the interaction
– The goal or outcome the actor wants to achieve
– The main sequence of interactions between actor and system
– Alternate or exception paths when things do not follow the main flow
– Preconditions and postconditions that define when the use case starts and ends

Use cases are widely used in requirements analysis, system design, and solution evaluation.

Use in industrial and manufacturing environments

In industrial operations and regulated manufacturing, a use case commonly refers to a concrete operational or information flow scenario, such as:

– A quality engineer recording a nonconformance in a QMS and triggering a corrective action workflow
– An operator starting a production order in an MES and reporting material consumption and downtime
– An automated test bench sending test results to an SPC or data historian system
– An ERP system requesting real-time WIP status from an MES for ATP (available-to-promise) calculations

These use cases may be documented at different levels of detail, ranging from high-level business scenarios (e.g., “Release a batch record for production”) to detailed system interactions (e.g., message exchanges between MES and PLCs).

Structure and documentation

Use cases in this domain are often represented using:

– **Textual descriptions**: Narrative or table-based format listing actor, triggers, main flow, alternate flows.
– **Diagrams**: UML use case diagrams or system context diagrams to show actors and their relationships to systems.
– **Scenarios or stories**: Concrete examples of how a shift, batch, or order is run using specific systems.

They may be grouped into use case catalogues for an MES, QMS, LIMS, historian, or other OT/IT platform.

Boundaries and exclusions

A use case:

– **Is not** the same as a process map, although a process map may contain multiple use cases.
– **Is not** a full functional specification; it describes interactions and goals, but not all technical details.
– **Is not** limited to software; it can cover interactions with equipment, manual steps, and paper artifacts, as long as they relate to a defined goal.

In regulated environments, use cases may inform but do not replace validation documentation, test cases, or formal procedures.

Common confusion and related terms

– **Use case vs. user story**: A user story is a brief, informal requirements statement (e.g., “As a line supervisor, I want to see OEE by shift…”). A use case is more structured and details interaction flows.
– **Use case vs. business case**: A business case explains why an initiative is undertaken (costs, risks, expected value). A use case explains how the solution will be used to achieve specific operational goals.
– **Use case vs. test case**: A test case is a specific, step-by-step test to verify a requirement. A use case provides the scenario from which many test cases can be derived.

Site-context application

On this site, use cases are generally discussed in relation to:

– Designing and selecting MES, QMS, LIMS, historian, and other OT/IT systems
– Describing interactions across ISA-95 style levels (ERP, MES, control, equipment)
– Clarifying how manufacturing, quality, maintenance, and regulatory workflows are supported by integrated systems

Use cases serve as a neutral way to describe these interactions without prescribing a specific product or implementation approach.