use-case-modeling

Use Case Modeling In A Nutshell

Use case modeling describes the proposed functionality of a system from the user perspective. Use case modeling was developed in 1986 by Ivar Jacobson and then released to the mainstream in his 1992 book Object-Oriented Software Engineering – A Use Case Driven Approach.

Understanding use case modeling

Upon release, the book popularized use case modeling as a technique to capture functional requirements in software development.

Use case modeling can be applied in the following scenarios:

  • Capturing system requirements.
  • Driving the implementation and generation of test cases.
  • Specifying the context of a system.
  • Validation of a systems architecture.
  • Developed by analysts with domain experts.

The core elements of a use case model

As a minimum, the use case model contains the following basic elements that are graphically depicted to show the relationship between each element:

Actor

Who is using the system? Actors encompass both human users and other computer systems.

They use a use case to perform some piece of work that is of value to the business.

The overall role and scope of each actor in the system are defined by the set of use cases they have access to.

Use case

What do the actors want to achieve?

A use case describes how the system should respond under various conditions to a request from an actor to deliver a specific goal.

Think of a use case as representing a discrete unit of meaningful work, such as the fulfillment of a new order or the registering of a new account.

A discrete use case may incorporate the functionality of another use case or extend a use case with its own behavior.

Associations

Or the relationship between actors and the particular use cases they interact with. 

System boundary

Which defines the system of interest with respect to the world around it.

The core elements of a use case description

Using elements of the use case model, a use case description provides a detailed, step-by-step account of the interaction between the actor and the system.

This sequence of steps is called a scenario.

Ultimately, the account should clearly show how the actor must initiate an action to derive value and achieve a goal.

To that end, it should contain the following:

Title

Which must communicate the goal of the use case. In the case of a student wanting to sign up for a volleyball class, the title may be “Register Student for Volleyball Class”.

Description

Or a summary of what the use case does.

Actors

Again, these are the people or systems who interact with the use case.

Preconditions

What needs to be in place before the use case can commence?

Postconditions

What conditions must be met for the scenario to end, either successfully or unsuccessfully?

Path

Or the step-by-step interaction between the actor and the system, divided into three types.

The primary path is the most commonly taken route to a successful conclusion.

The alternate path is a less commonly used route to the same conclusion.

The exception path leads to an unsuccessful conclusion and may incorporate an error message or further instruction.

Date of creation and revision history

This chronology helps determine how old the use case is when undertaking document analysis.

Priority and frequency of use

How important is the use case? How often is it executed? Both are useful in solution planning.

Use case modeling examples

In the final section, let’s conclude by outlining some basic use case modeling examples.

Airport check-in and security screening

  • Business actors – passenger, tour guide, passenger with special needs, minor passenger (child). Each of these actors plays an external role with respect to the airport business.
  • Business use cases – individual passenger check-in, group check-in, passenger security screening, luggage handling. These describe business process functions that occur within the airport and serve the needs of users. 

As we noted earlier, a discrete use case may incorporate the functionality of another use case or extend one with its own behavior.

In this example, the discrete use cases “luggage check-in” and “luggage handling” extend the business use case “individual passenger check-in”.

Since some individuals may be traveling without luggage, these use cases become optional.

Automated teller machine

In the case of an automated teller machine (ATM), a customer of the bank (actor) uses the machine in several different use cases. These include:

  • Deposit funds.
  • Transfer funds.
  • Withdraw money.
  • Check balance.
  • Pay income tax. 
  • Print recent transactions.

Another actor is the ATM technician with the following use cases: maintenance, repair, and security check.

The use cases of both the ATM technician and the bank customer involve the “bank” actor – irrespective of whether the use case is related to banking transactions or maintenance.

Online shopping

A consumer that uses a website to purchase a product or service online is the actor, or more formally, the “online customer”.

Use cases in this scenario may include:

  • Make a purchase.
  • View items.
  • Register details.
  • Checkout.

For eCommerce companies, use case diagrams may be a little more difficult to define.

For example, the “view items” use case may only be relevant if the customer wants to look at an item without purchasing it.

This particular use case could also be incorporated into the “make purchase” use case if so desired.

It is important to note that in this example, the “checkout” use case is a component of making a purchase and is not available by itself.

Known as an included use case, “checkout” relies on the support and functionality of the base use case “make a purchase”. 

The “view items” use case may also be extended by use cases such as “browse catalog”, “search for items”, “add to wedding registry”, or “add items to shopping cart”.

Again, these are all extending use cases because they add functionality to the process of a customer finding a product online.

In addition to the online customer actor, there are also several other actors. These include:

  • New customer.
  • Registered customer.
  • Identity provider.
  • Credit payment service.
  • Service authentication.
  • Afterpay.

If we return to the “checkout” use case, for example, we see that it includes multiple required use cases.

The online customer (actor) authentication process occurs via the use cases of “user cookie” or “single sign-on” (SSO). Note that “service authentication” is involved in both these use cases, with the SSO functionality also requiring an external identity provider.

Key takeaways:

  • Use case modeling describes the proposed functionality of a system from the perspective of the user.
  • At the very least, a use case model should contain four basic elements: actor, use case, associations, and system boundary.
  • Use case modeling necessitates that a use case description is written. This is a series of steps that provides an account of the interaction between the actor and the system.

Connected Business Frameworks

Other connected frameworks

Porter’s Five Forces

porter-five-forces
Porter’s Five Forces is a model that helps organizations to gain a better understanding of their industries and competition. Published for the first time by Professor Michael Porter in his book “Competitive Strategy” in the 1980s. The model breaks down industries and markets by analyzing them through five forces.

BCG Matrix

bcg-matrix
In the 1970s, Bruce D. Henderson, founder of the Boston Consulting Group, came up with The Product Portfolio (aka BCG Matrix, or Growth-share Matrix), which would look at a successful business product portfolio based on potential growth and market shares. It divided products into four main categories: cash cows, pets (dogs), question marks, and stars.

Balanced Scorecard

balanced-scorecard
First proposed by accounting academic Robert Kaplan, the balanced scorecard is a management system that allows an organization to focus on big-picture strategic goals. The four perspectives of the balanced scorecard include financial, customer, business process, and organizational capacity. From there, according to the balanced scorecard, it’s possible to have a holistic view of the business.

Blue Ocean Strategy 

blue-ocean-strategy
A blue ocean is a strategy where the boundaries of existing markets are redefined, and new uncontested markets are created. At its core, there is value innovation, for which uncontested markets are created, where competition is made irrelevant. And the cost-value trade-off is broken. Thus, companies following a blue ocean strategy offer much more value at a lower cost for the end customers.

Scenario Planning

scenario-planning
Businesses use scenario planning to make assumptions on future events and how their respective business environments may change in response to those future events. Therefore, scenario planning identifies specific uncertainties – or different realities and how they might affect future business operations. Scenario planning attempts at better strategic decision making by avoiding two pitfalls: underprediction, and overprediction.

Read Next: SWOT AnalysisPersonal SWOT AnalysisTOWS MatrixPESTEL AnalysisPorter’s Five ForcesTOWS MatrixSOAR Analysis.

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