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UML and SysML Diagrams

Ngenaire's diagramming workspace lives at /modeling (sidebar: Model → Diagrams). Every diagram is authored from PlantUML source, rendered to a live Preview, and can be linked to a ConOps Link and Flow-down Requirements. You can write the source yourself or ask the AI to draft it for you.

Diagram types

When you create a diagram you pick a Diagram Type from a single grouped list. The picker offers three families.

UML (14 types)

  • Use Case — actors and their goals.
  • Sequence — ordered messages between participants over time.
  • Activity — workflow with branches, forks, and joins.
  • State Machine — modal behavior of a single object.
  • Communication — objects with numbered messages.
  • Interaction Overview — high-level flow linking interaction fragments.
  • Timing — state changes against a time axis.
  • Composite Structure — internal structure of a classifier.
  • Deployment — artifacts deployed onto physical nodes.
  • Package — structural grouping of model elements.
  • Profile — UML extensions for a specific domain.
  • Class — types and their relationships.
  • Object — an instance-level snapshot.
  • Component — components and their interfaces.

A ConOps Support helper type is also available for diagrams that illustrate a concept-of-operations narrative.

SysML (9 types)

  • Block Definition (BDD) — system blocks and their relationships.
  • Internal Block (IBD) — internal structure and connectors of a block.
  • Use Case — SysML use case view.
  • Sequence — SysML interaction view.
  • Activity — SysML behavior view.
  • State Machine — SysML state behavior.
  • Requirement — relationships among requirements.
  • Parametric — constraint relationships between block parameters.
  • Package — system structure grouping.

Architecture (2 types)

  • Context Diagram — a system-boundary view that shows the system as a whole against the external actors, systems, and environment it interacts with. It is authored exactly like the other diagram types on this page (PlantUML source plus live preview); there is no separate page for it.
  • Data Flow Diagram — listed here for completeness, but a DFD has its own dedicated canvas editor. See Data Flow Diagram.

Walkthrough

1. Open the workspace

  1. Click Model → Diagrams in the sidebar (or go to /modeling).

2. Create a diagram

  1. Click New to start a fresh diagram.
  2. Enter a Title and an optional Description.
  3. Choose a Diagram Type from the grouped list.
  4. Optionally set a ConOps Link to tie the diagram to a concept-of-operations document.
  5. Optionally tick Flow-down Requirements to associate the diagram with the requirements it realizes.

3. Edit the source

The editor is a split view: the diagram metadata and the PlantUML Source field on one side, and a live Preview on the other.

  1. Type or paste PlantUML into the PlantUML Source field.
  2. The Preview re-renders as you edit so you can see the result immediately.

4. Generate with AI

Ask the AI Assistant to draft a diagram from a description and it will return ready-to-edit PlantUML source. Useful prompts:

Generate a sequence diagram for the user authentication flow in CONOPS section 3.

Create a SysML BDD for the avionics subsystem with flight control, navigation, and telemetry sub-blocks.

Draft a context diagram showing our system and every external actor it exchanges data with.

Treat AI output as a starting draft — review and refine the source before saving.

5. Validate the source

Ngenaire validates PlantUML source so malformed diagrams are caught before they are saved. If the source can't be rendered, the Preview shows an error and explains that the raw source can still be saved while you fix it.

6. Save, update, or delete

  1. Click Save to persist the diagram.
  2. Reopen any diagram from the list to edit it, then save again to update.
  3. Use the delete action to remove a diagram you no longer need.

Tips

  • Pick the smallest type that conveys the idea. A use case is often clearer than a class diagram for early scoping.
  • Link as you draw. Setting Flow-down Requirements while authoring avoids a manual reconciliation pass later.
  • Use the Context Diagram first. Establishing the system boundary up front makes every downstream diagram easier to scope.

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