Module 1: Foundations

Imagine building a large factory. Before construction starts, you need many drawings — floor plans, electrical diagrams, plumbing layouts… each describes one aspect of the factory. Systems engineering is the same. Engineers building complex systems (aircraft, rockets, medical devices) need a structured language to describe every aspect of the system before it is built. SysML v2 is that language.

Who created SysML v2?

SysML v2 was created by the Object Management Group (OMG) in collaboration with INCOSE (the International Council on Systems Engineering). It was officially released in 2024 as OMG specification ptc/2024-05-04 — the most current version.

What was wrong with SysML v1?

SysML v1 was released in 2006. It was adapted from UML (a software design language), which brought a lot of historical baggage irrelevant to systems engineering. SysML v2 is a clean redesign from first principles.

KerML stands for Kernel Modeling Language. It is itself an independent OMG standard (ptc/2024-05-05). You usually do not write KerML directly — just as you do not build a water treatment plant before renovating your house — but understanding KerML's key concepts helps you understand why SysML v2 works the way it does.

KerML core concepts — step by step

Each concept below builds on the one before it.

Summary of KerML core construct relationships

The diagram below shows how all KerML core constructs relate. You do not need to memorise it immediately — as you progress through the series, each box will become familiar.

Reading guide: hollow triangle arrows mean "specialises" (subtype → supertype); dashed blue arrows mean "subsetting"; blue boxes are abstract types, green boxes are concrete types.

SysML v2 is organised into four layers:

Definitions — describing "what something is"

A definition is a reusable template. Write it once, reference it in many places. Key SysML v2 definition keywords:

• part def — defines a structural component (like a blueprint for a part)
• item def — defines something that flows between parts (signals, data, fluids)
• port def — defines a connection point (like a socket standard)
• action def — defines an action or function (like defining an operation step)
• state def — defines a state machine behaviour
• requirement def — defines a requirement type (template format)
• attribute def — defines a value type or attribute (e.g. temperature, mass)

Usages — describing "where it is used"

Usages place a definition into a specific context. Usage keywords correspond one-to-one with definition keywords — just remove def:

• part — a specific structural component (this system's particular part)
• item — a specific flowing element
• port — a specific connection point on a part
• action — a specific operation step in a flow
• state — a specific state in a state machine
• requirement — a specific requirement
• attribute — a specific attribute slot (waiting to be assigned a value)

A complete example

// ── Step 1: Definitions (write the 'menu') ─────────────────────

part def Battery {
    attribute capacity : Real;    // battery has a capacity (Wh)
    attribute voltage  : Real;    // battery has a voltage (V)
}

part def Motor {
    attribute maxRPM : Real;
    port powerIn : ~ElectricalPort;  // motor has a power input port
}

part def Drone {
    part battery : Battery;       // usage — drone has one Battery
    part motor1  : Motor;         // usage — drone has four Motors
    part motor2  : Motor;
    part motor3  : Motor;
    part motor4  : Motor;
}

// ── Step 2: Usage (place a 'order') ───────────────────────────

part missionDrone : Drone;        // this is one specific mission drone

SysML v1 only had a graphical language (boxes and arrows). SysML v2 adds a standard textual notation called STN (SysML Textual Notation). Benefits: can be written in any text editor, version-controlled in Git, and processed by code.

Core syntax rules

If you have no prior SysML v1 experience, you may skip this section or treat it as a vocabulary preview. The table below shows common SysML v1 concepts and their SysML v2 equivalents.

Congratulations on completing Module 1! Here is a recap of the core ideas:

• SysML v2 is a standardised "drawing language" for engineers to design complex systems, released by OMG in 2024.
• SysML v2 is not based on UML — it is built on a new foundation, KerML (Kernel Modeling Language), with more precise concepts.
• KerML defines the most fundamental constructs: Element, Type, Feature, Classifier, Connector, Relationship.
• SysML v2 has four layers: mathematical foundation (L0) → KerML (L1) → SysML language (L2) → standard library (L3). You work in L2 day-to-day.
• The most important distinction: definition (def) = template; usage (no def) = one concrete application in a specific context.
• SysML v2 adds a textual notation (STN) — graphical and textual forms are interchangeable.
• If you know SysML v1: Block → part def, Activity → action def, most concepts have direct equivalents.