Compare Capabilities of Model Component Types

Before you implement a piece of your system using a specific component type, consider whether the component type satisfies your modeling requirements.

Component ConsiderationModeling Requirements
Development Process
  • Component reuse

  • Shared data

  • Instance-specific edits

  • Version control and configuration management

  • Intellectual property protection

  • Unit testing

Performance Requirements
  • Incremental model loading

  • Build artifact reuse

  • Reduced memory usage for large models

  • Artificial algebraic loop elimination

Features
  • Compatible configuration parameter settings

  • Signal property specification at interfaces

  • Bus specification

  • State initialization

  • Code generation

Development Process

Modeling RequirementSubsystemsLinked SubsystemsSubsystem ReferencesModel References
Component Reuse

Not supported

While you can copy a subsystem to reuse it in a model, the copies are independent of each other.

When you edit a subsystem, the changes apply to the parent model file.

To create or change a subsystem, you must open the parent model, which can lead to file contention when multiple people want to work in the model.

Supported

You save the parent library block of a linked block in a separate file from the model that links to it. Using separate files helps to avoid file contention.

You can link to the same parent library block multiple times in multiple models without creating copies.

Managing library links adds some overhead, such as managing broken, disabled, or parameterized links.

Supported

You save a referenced subsystem in a separate file from the model that references it. Using separate files helps to avoid file contention.

You can reference the same subsystem multiple times in multiple models without creating copies.

Supported

You save a referenced model in a separate file from the model that references it. Using separate files helps to avoid file contention.

You can reference the same model multiple times in multiple models without creating copies. See Model Reuse.

Shared Data

Supported

You can share data among instances by defining the data outside the component. For example, by using a data store in a common parent subsystem.

Supported

Same behavior as subsystems.

Supported

Same behavior as subsystems.

Supported

You can share data among instances of the referenced model by creating a data store inside the model. See Share Data Among Referenced Model Instances.

Instance-Specific Edits

Supported

Subsystem copies are independent of each other.

Supported

When you edit a parent library block, the changes apply to the library file and propagate to all blocks that link to that block.

To edit an instance of the block, you can disable the library link.

You cannot disable library links when the parent library block has restricted write access.

Not supported

When you edit an instance of a referenced subsystem, the changes apply to the subsystem file and propagate to all other instances of the referenced subsystem.

Not supported

When you edit an instance of a referenced model, the changes apply to the model file and propagate to all other instances of the referenced model.

Version Control and Configuration Management

Not supported

You cannot directly place subsystems in a source control system.

To reduce file contention and use separate version control for each subsystem, use a subsystem reference.

Supported

You can place library files in a source control system.

To provide individual version control for each library block, use subsystem references and model references in the library. When you drag these blocks from the library into your model, they reference the subsystem file or model file.

Forwarding tables allow you to map old library blocks to new versions of the blocks.

Supported

You can place subsystem files in a source control system.

Supported

You can place model files in a source control system.

Intellectual Property Protection

Not supported

Use model references instead.

Not supported

Same behavior as subsystems.

Not supported

Same behavior as subsystems.

Supported

Protected models obscure model contents, which can be useful when distributing models.

Creating a protected model requires a Simulink® Coder™ license. Using a protected model does not require a Simulink Coder license.

Unit Testing

Supported

Subsystems are dependent on their context in a model. If the context of a subsystem changes, such as the data type of an input signal, the related test harness must be updated.

For subsystems that are not atomic, the test harness may use different block execution orders, due to virtual boundaries.

For tools that support authoring, managing, and executing systematic, simulation-based tests of subsystems, see Create Test Harnesses and Select Properties (Simulink Test).

To measure how thoroughly model components are tested, see Model Coverage (Simulink Coverage).

Supported

Same behavior as subsystems.

Supported

Same behavior as subsystems.

Supported

You can test a referenced model independently to isolate behavior by simulating it as a top model.

You can use a data-defined test harness, with MATLAB® test vectors and direct coverage collection.

For tools that support authoring, managing, and executing systematic, simulation-based tests of subsystems, see Create Test Harnesses and Select Properties (Simulink Test).

To measure how thoroughly model components are tested, see Model Coverage (Simulink Coverage).

Performance Requirements

Modeling RequirementSubsystemsLinked SubsystemsSubsystem ReferencesModel References
Incremental Model Loading

Not supported

Loading a model loads all subsystem contents that are saved in the model.

Supported

Simulink incrementally loads a library at the point needed during editing, updating a diagram, or simulating a model.

Supported

Simulink incrementally loads a referenced subsystem at the point needed during editing, updating a diagram, or simulating a model.

Supported

Simulink incrementally loads a referenced model at the point needed during editing, updating a diagram, or simulating a model.

Build Artifact Reuse

Not supported

Build artifacts, such as simulation targets, are not generated for subsystems.

Not supported

Same behavior as subsystems.

Not supported

Same behavior as subsystems.

Supported

You can share and reuse build artifacts, such as simulation targets, using Simulink cache files. For more information, see Share Build Artifacts for Faster Simulation and Code Generation.

Reduced Memory Usage for Large Models

Not supported

Subsystems do not reduce memory usage for simulation and code generation.

Not supported

Linked subsystems do not reduce memory usage for simulation and code generation.

Simulink duplicates library block instances during block update.

Not supported

Subsystem references do not reduce memory usage for simulation and code generation.

Simulink duplicates subsystem reference instances during block update.

Supported

Models referenced in accelerator mode reduce memory usage for simulation and code generation because Simulink incrementally loads compiled versions of them.

Artificial Algebraic Loop Elimination

Supported

Subsystems that are not atomic avoid artificial algebraic loops.

If a subsystem is atomic, you can try to eliminate artificial algebraic loops by enabling the Subsystem block parameter Minimize algebraic loop occurrences.

Supported

Same behavior as subsystems.

Supported

Same behavior as subsystems.

Supported

You can try to eliminate artificial algebraic loops by enabling Configuration Parameters > Model Referencing > Minimize algebraic loop occurrences.

Features

Modeling RequirementSubsystemsLinked SubsystemsSubsystem ReferencesModel References
Compatible Configuration Parameter Settings

Supported

Subsystems use the configuration parameter settings of the model that contains them.

Supported

Same behavior as subsystems.

Supported

Same behavior as subsystems.

Supported

Configuration parameter settings can generally be different for a parent model and its referenced models. For compatibility information, see Set Configuration Parameters for Model Hierarchies.

Signal Property Specification at Interfaces

Supported

You can specify signal properties at a subsystem interface.

For signal properties that you do not specify, subsystems inherit the signal properties from their context. Propagation of signal properties can lead to Simulink using signal properties that you do not anticipate.

Supported

Same behavior as subsystems.

Supported

Same behavior as subsystems.

Supported

You must specify most signal properties at a referenced model interface.

Referenced models are context-independent with a defined boundary, so they do not inherit most signal properties.

Referenced models can inherit discrete sample times when the referenced model is sample-time independent.

Bus Specification

Supported

You can use a Simulink.Bus object to specify the data type of a bus that passes into a subsystem.

Subsystems do not require the use of Bus objects for virtual buses.

Supported

Same behavior as subsystems.

Supported

Same behavior as subsystems.

Supported

You can use a Simulink.Bus object to specify the data type of a bus that passes into a referenced model.

Model references do not require the use of Bus objects for virtual buses when you use In Bus Element and Out Bus Element blocks.

State Initialization

Supported

You can initialize states of subsystems.

Supported

Same behavior as subsystems.

Supported

Same behavior as subsystems.

Supported

You can initialize states from the top model using either the structure format or structure-with-time format. For more information, see State Information for Referenced Models.

Code Generation

Supported

For information on subsystem code generation, see Control Generation of Functions for Subsystems (Simulink Coder).

Supported

For information on linked subsystem code generation, see Control Generation of Functions for Subsystems (Simulink Coder).

Supported

Same behavior as subsystems.

Supported

For information on referenced model code generation, see Code Generation of Referenced Models (Simulink Coder).

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