Model Modification

This section describes how to safely modify using the Open API.

All model changes must be executed within a controlled context to ensure:

• Consistency of the model
• Proper command tracking
• Support for undo/redo operations

The platform provides two approaches for performing model modifications:

• The (2026x Refresh1) Editing API (recommended)
• The (2026x Refresh1) SessionManager API (lower-level control)

Model Modification Concepts

Before modifying a model, it is important to understand the core concepts:

• Commands
  Each modification is recorded as a command for undo/redo
• Command History
  Tracks executed changes and enables rollback
• Sessions
  Define the scope in which model changes are applied

These mechanisms ensure that all changes are safe, traceable, and reversible.

Choosing an API

Use the Editing API (Recommended)

• Automatically manages commands and command history
• Simpler and safer to use
• Best for most plugin and automation scenarios

See: (2026x Refresh1) Editing API

Use SessionManager (Advanced)

• Provides manual control over sessions
• Requires explicit session lifecycle management
• Useful for legacy integrations or specialized workflows

See: (2026x Refresh1) SessionManager API

Example Comparison

import com.dassault_systemes.modeler.foundation.editing.Editing;
import com.nomagic.magicdraw.openapi.uml.SessionManager;

Editing editing = Editing.getInstance(project);

// Recommended approach (Editing API)
editing.execute("Create element", () -> {
    // model changes here
});
 
// Manual approach (SessionManager)
SessionManager.getInstance().createSession(project, "Edit");
try {
    // model changes here
} finally {
    SessionManager.getInstance().closeSession(project);
}

Key Takeaways

• All model changes must occur within a controlled execution context
• Prefer the Editing API for most use cases
• Use SessionManager only when you need explicit control