computer science

Requirement diagram

Requirement diagram is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Requirement diagram rather than just read about it. In short: A requirement diagram is a diagram specially used in SysML in which requirements and the relations between them and their relationship to other model elements are shown as discussed in the following paragraphs. Derive requirement relationship If a requirement is derived from another requirement, their relation is named "derive requirement relationship".

Key takeaways

Requirement diagram belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Requirement diagram to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Requirement diagram from memory before moving on to harder problems.

Reference excerpt

Derive requirement relationship If a requirement is derived from another requirement, their relation is named "derive requirement relationship".

Namespace containment If a requirement is contained in another requirement, their relation is named "namespace containment".

Satisfy relationship If a requirement is satisfied by a design element, their relation is named "satisfy relationship".

Copy relationship If a requirement is a copy of another requirement, their relation is named "copy relationship".

Verify relationship If there exists a relation between a requirement and a test case verifying this requirement, their relation is named "verify relationship".

Test case A test case is defined by a flow checking whether the system under consideration satisfies a requirement.

Refine relationship If a requirement is refined by other requirements / model elements, the relation is named "refine relationship".

Trace relationship If there exists a relation between a requirement and an arbitrary model element traced by this requirement, their relation is named "trace relationship".

References Weilkiens, Tim (2008). Systems Engineering with SysML/UML: Modeling, Analysis, Design. Morgan Kaufmann / The OMG Press. ISBN 0-12-374274-9.

Illustrations

Worked examples

Example 1 — a first encounter with Requirement diagram

Start with the simplest possible case. Write down what Requirement diagram claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Requirement diagram before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Requirement diagram ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Requirement diagram

In research: Requirement diagram appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Requirement diagram in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Requirement diagram is common in secondary-school and first-year university syllabi. It links to neighbouring topics Software requirements, Systems Modeling Language, Systems engineering, so understanding it makes those chapters shorter.
In everyday life: Look for Requirement diagram outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Requirement diagram in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Requirement diagram means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Requirement diagram out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Requirement diagram in simple terms?

A requirement diagram is a diagram specially used in SysML in which requirements and the relations between them and their relationship to other model elements are shown as discussed in the following paragraphs. Derive requirement relationship If a requirement is derived from another requirement, th…

Why does Requirement diagram matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Requirement diagram?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Requirement diagram.