Architecture, Models, Frameworks, and Methodologies in MBSE

When working in Model-Based Systems Engineering (MBSE) or Enterprise Architecture, several terms are often used interchangeably even though they represent very different concepts.

Understanding the difference between architecture, models, frameworks, methodologies, and ontologies is essential for organizing system models and managing complexity across engineering teams.

This article explains the core terminology used in MBSE and enterprise architecture.

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What Is Architecture?

Architecture describes the fundamental organization of a system.

According to ANSI/IEEE 1471-2000 and ISO/IEC 42010, architecture is defined as:

“The fundamental organization of a system embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution.”

In simple terms, architecture explains:

• what components exist in a system

• how those components interact

• the governing design principles of the system

Architecture provides the blueprint of the system.

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What Is an Architecture Description?

An architecture description is the set of artifacts used to document and communicate the architecture.

According to IEEE 1471, an architecture description is:

A collection of artifacts or work products used to describe an architecture.

These artifacts may include:

• system models

• diagrams

• documents

• requirements

• analysis results

In MBSE, architecture descriptions are typically represented through models instead of documents.

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What Is an Architecture Model?

An architecture model is a representation of the system architecture.

Architecture models usually contain multiple types of models, including:

• descriptive models

• analytical models

• requirements models

• behavioral models

• structural models

Together these models provide a comprehensive digital representation of the system.

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What Is a Metamodel?

A metamodel is often described as a “model of a model.”

It defines:

• the modeling conventions

• element types

• relationships between elements

• constraints used in the model

For example, the SysML specification acts as a metamodel because it defines:

• blocks

• requirements

• activities

• relationships between elements

Metamodels provide the rules that govern how models are constructed.

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What Is a Framework?

A framework provides the structural foundation for organizing information.

A framework typically defines:

• assumptions

• concepts

• values

• practices

• structural viewpoints

Frameworks help guide decision-making, architecture development, and system design.

In architecture work, frameworks provide structure, not process.

In other words:

Framework = Structure

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What Is a Methodology?

A methodology defines the process used to perform engineering activities.

It provides guidance on:

• tasks that should be performed

• the sequence of activities

• tools and techniques used

• resources required to execute the work

Martin (1996) defines a methodology as:

“The collection of related processes, methods, and tools used to support a specific discipline.”

In MBSE, a methodology describes how system models are developed and evolved throughout the lifecycle.

Unlike frameworks, methodologies define process and workflow.

Methodology = Process

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Widely Known MBSE Methodologies

Several MBSE methodologies are commonly referenced in systems engineering literature.

These methodologies provide different approaches for structuring system modeling activities.

Examples include:

• INCOSE Object-Oriented Systems Engineering Method (OOSEM)

• IBM Rational Harmony-SE

• IBM Rational Unified Process for Systems Engineering (RUP-SE)

• Vitech MBSE Methodology

• JPL State Analysis (SA)

• Object-Process Methodology (OPM)

• SYSMOD

These methodologies help guide engineers in creating system models and managing system complexity.

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What Is an Enterprise Architecture Framework (EAF)?

Enterprise Architecture Frameworks help organizations manage large systems and multiple levels of abstraction.

Bernard (2004) describes an EAF as:

“A structure for organizing information that defines the scope of the architecture and how the areas of the architecture relate to each other.”

Enterprise architecture frameworks are used to organize architecture descriptions across large organizations.

Examples include:

• DoDAF — Department of Defense Architecture Framework

• MODAF — Ministry of Defence Architecture Framework

• NAF — NATO Architecture Framework

• TOGAF — The Open Group Architecture Framework

• FEAF — Federal Enterprise Architecture Framework

• Zachman Framework

These frameworks provide structured ways to organize architecture information across complex enterprises.

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What Is an Ontology?

An ontology defines the shared conceptual understanding of a domain.

It formally describes:

• types of objects

• relationships between objects

• constraints on those relationships

In engineering environments, ontologies help ensure that different teams interpret system concepts consistently.

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What Is a Schema?

A schema defines how data is structured and stored within a system.

Schemas are commonly used in databases and data models to organize information.

Examples include:

• database tables

• relationships between data fields

• rules for storing and retrieving information

Schemas help represent specific problem domains in structured data form.

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How These Concepts Relate

A useful way to understand these concepts is to recognize the difference between structure and process.

The Zachman Framework explains this relationship clearly:

“The Framework is the ontology for describing the enterprise. The framework is a structure whereas a methodology is a process. Structure establishes definition while process provides transformation.”

In other words:

When these elements are used together, engineering teams can build predictable and repeatable system development processes.

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Final Thoughts

Modern Model-Based Systems Engineering relies on the integration of architecture, models, frameworks, and methodologies.

Frameworks provide structure.
Methodologies provide process.
Models provide the representation of the system.

When these elements are aligned, organizations can manage system complexity more effectively and produce repeatable, scalable engineering results.