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UML, or Unified Modeling Language, is a standardized general-purpose modeling language in the field of software engineering. It is a visual language used to model, visualize, and document software systems. UML includes a set of graphic notation techniques to create visual models of object-oriented software systems. It is not a programming language but tools can be used to generate code in various languages using UML diagrams. UML has a direct relation with object-oriented analysis and design. It was developed by Grady Booch, Ivar Jacobson, and James Rumbaugh at Rational Software during 1994–1995.

Ask the right questions secure the right UML talent among an increasingly shrinking pool of talent.

First 20 minutes

General UML app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in UML application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you use UML to model a system?

I would begin with use case diagrams to understand the system's functionality. Then, I would use class diagrams to model the system's structure, sequence diagrams to model interactions, and state diagrams to model the behavior of system entities. I would use component and deployment diagrams to model the system's architecture.

What are the basic building blocks of a UML diagram?

The basic building blocks of a UML diagram are things (classes, interfaces), relationships (associations, generalizations), and diagrams (class, sequence, use case).

Describe the difference between aggregation and composition in UML.

Aggregation is a relationship where a whole is made up of parts, but the parts can exist independently of the whole. Composition, on the other hand, is a stronger form of aggregation where the parts cannot exist independently of the whole.

How would you use a sequence diagram to model an interaction?

I would use a sequence diagram to model an interaction by representing the objects participating in the interaction as boxes along the top of the diagram, and the messages exchanged between them as arrows arranged in a timeline from top to bottom.

What are the different types of relationships in UML?

The different types of relationships in UML are association, aggregation, composition, dependency, generalization, and realization.

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What you’re looking for early on

Does the candidate have a strong understanding of UML (Unified Modeling Language)?

Has the candidate demonstrated the ability to communicate effectively?

Is the candidate able to solve problems creatively?

Has the candidate shown the ability to work well in a team?

Next 20 minutes

Specific UML development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between a class diagram and an object diagram.

A class diagram models the static structure of a system, showing the classes in the system and the relationships between them. An object diagram, on the other hand, is a snapshot of the system at a particular point in time, showing instances of classes and the values of their attributes.

How would you use a state diagram to model the behavior of a system entity?

I would use a state diagram to model the behavior of a system entity by representing the states the entity can be in as circles, and the transitions between states as arrows.

What are the different types of diagrams in UML?

The different types of diagrams in UML are use case diagrams, class diagrams, object diagrams, sequence diagrams, collaboration diagrams, statechart diagrams, activity diagrams, component diagrams, and deployment diagrams.

Describe the difference between generalization and realization in UML.

Generalization is a relationship between a general class (the superclass) and a more specific class (the subclass). Realization, on the other hand, is a relationship between a specification and its implementation.

How would you use a use case diagram to model a system's functionality?

I would use a use case diagram to model a system's functionality by representing the system's actors and their interactions with the system as use cases.

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At this point, a skilled UML engineer should demonstrate strong problem-solving abilities, proficiency in UML programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with UML.

What does this simple UML diagram represent?
{ 'Class': 'Car', 'Attributes': ['color', 'model'], 'Methods': ['start()', 'stop()'] }
This UML diagram represents a 'Car' class with two attributes - color and model, and two methods - start() and stop().
What does this UML association represent?
{ 'Class1': 'Person', 'Class2': 'Car', 'Association': 'owns' }
This UML association represents a relationship between two classes, 'Person' and 'Car'. The 'owns' association indicates that a 'Person' owns a 'Car'.
What does this UML diagram represent in terms of array manipulation?
{ 'Class': 'ArrayManipulation', 'Attributes': ['array'], 'Methods': ['sort()', 'reverse()', 'findMin()', 'findMax()'] }
This UML diagram represents a 'ArrayManipulation' class with one attribute - array, and four methods - sort(), reverse(), findMin(), and findMax(). These methods are used to manipulate the array.
What does this UML diagram represent in terms of threading or concurrency?
{ 'Class': 'ThreadExample', 'Attributes': ['thread1', 'thread2'], 'Methods': ['start()', 'stop()', 'join()'] }
This UML diagram represents a 'ThreadExample' class with two attributes - thread1 and thread2, and three methods - start(), stop(), and join(). These methods are used to control the execution of threads.

Wrap-up questions

Final candidate for UML Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle UML application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the different types of messages in a sequence diagram?

The different types of messages in a sequence diagram are synchronous messages, asynchronous messages, and reply messages.

Describe the difference between a sequence diagram and a collaboration diagram.

A sequence diagram emphasizes the time ordering of messages, while a collaboration diagram emphasizes the structural organization of the objects.

How would you use a deployment diagram to model a system's architecture?

I would use a deployment diagram to model a system's architecture by representing the system's nodes as boxes and the communication paths between them as lines.

UML application related

Product Perfect's UML development capabilities

Beyond hiring for your UML engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in UML projects, and can engage in multiple capacities.

UML Consultive assessments

UML Application Conversion Assessment UML Application Integration Assessment UML Data & Database Integration Assessment

Custom UML development projects

Custom UML App Conversion UML Custom App Development Process App UI Design for UML Facelifts

Hiring guide for UML Engineers

UML Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the UML engineer at this point.

UML Consultive assessments

Custom UML development projects