Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Defining requirements

From: Foundations of Programming: Object-Oriented Design

Video: Defining requirements

This first step can have other names, even just analysis, but Requirements is a good word. What is the application required to do, what must it do? Now the core of your requirements or what are called functional requirements, literally, what are the features, the capabilities of the application? What does it need to do? But there are other non-functional requirements like what kind of help or documentation needs to be provided? Are there legal requirements? If you're building a system that does banking transactions or stores healthcare data, then there may be laws that you need to comply with.

Defining requirements

This first step can have other names, even just analysis, but Requirements is a good word. What is the application required to do, what must it do? Now the core of your requirements or what are called functional requirements, literally, what are the features, the capabilities of the application? What does it need to do? But there are other non-functional requirements like what kind of help or documentation needs to be provided? Are there legal requirements? If you're building a system that does banking transactions or stores healthcare data, then there may be laws that you need to comply with.

And do you know those details? If you don't, who does? Performance requirements, response time, how many people does this app need to support simultaneously? Support requirements, if there's an issue with the web application at 2 a.m. on a Sunday morning, what needs to happen? And security can be considered either non-functional or functional requirement depending on the app. Now if you're doing the app for someone else, you'd get a lot of this from your customer, your client. Now if you are the driving force behind the app, if it's your idea, it's easy to think that you've thought about this, you know all this already, you can skip this step, but that's almost always a mistake.

Most solo developers or small teams have a dozen semi-formed ideas about some of the cool features the application could have. But we're trying to get away from that here. We can't design half a feature. So not the hundred different things it might do or could do, but at least initially what the app must do. Now requirements can be phrased very simply. You'll often see requirements begin with the phrase system must or application must or program must, depending on which term you prefer.

So system must display the heart rate, temperature, and blood pressure of a patient connected to the monitor. Application must allow a user to search by a customer's last name, telephone number, or order number. Program must allow receipts to be generated via email. You can do these as fairly short, simple, succinct statements, must allow the user to create a 140-character message, must continue to function without network connection. Or you could have something a little bit more complicated as long as it's very specific.

Now on the other hand, what we could also have are a few non-functional requirement examples. So system must respond to searches within 2 seconds. This is not actually a feature, but it is something that is required. Helpdesk should be available by telephone, Mon-Fri, 8 a.m. to 6 p.m. We can talk about the laws that we need to comply with or uptime of response time. All these are considered non-functional requirements. Now the bigger the application and the bigger your organization, the more formal you're going to need to be about all of this.

Now what we're doing here-- typically called requirements analysis--is a discipline all of in itself, and if you need to take deeper than we can cover here, there are some great books on the subject that will provide a structure for doing this. Now one common approach if you need to be a bit more formal is something called FURPS or FURPS+. It sounds intimidating, really isn't. It's a simple mnemonic, it's a checklist, it's designed to prompt you, did you think about this? So starting with the letter F we have Functional requirements, the features of the app.

Usability, help, documentation, tutorials. Reliability, disaster recovery, acceptable failure rates. Are these things you need to think about now or later or not at all? Performance, availability, capacity, resources, and supportability, not just things like who maintains it, but also could this be internationalized? Would it need to be internationalized? Now often our non-functional requirements are all about the -ilities, maintainability, reliability, usability, availability.

Now in FURPS+ we add four more. We have the idea of Design requirements, it's a constraint. So must be an iPhone app or must require relational database. Not actually a feature of the app, but something you need to pay attention to. We can have Implementation requirements, so things like what's the language we're going to use? Do we have to comply with certain standards or perhaps even a methodology? Now an Interface requirement typically refers not to the user interface but to any external system that you need to interface with, and you need to specify this now.

And a Physical requirement specifies an actual physical constraint. Everything from needs to run on a device with a camera to must ship with 50 Gigabytes of DVDs. But this is not instructions, it's simply a checklist. But again, first time through what you're going for is the absolute minimum set of requirements, and that's the concept to hang on to here. Not what is nice to have, not what is optional, not all the dream features of you or your customer, only what is required.

Now it's a common mistake that people try to be exhaustive to try and have answers for everything upfront. But in an agile-iterative approach, it's perfectly acceptable to go through this and have not applicable or to be determined for some of these. And I'll say this again, you're not looking for completeness or even expecting it. Don't expect to write this once and freeze it, your requirements will change. Now technically what we're doing here has nothing to do with object orientation. If at this stage you use words like polymorphism or abstraction, you're way off base.

We don't even expect the word class or object here. So what do we expect from this? Something written down, anything from a set of bullet points on a whiteboard to a complete requirements document in a more formal process. But we need something to feed into the next part of our process to allow us to describe the application in a little bit more detail.

Show transcript

This video is part of

Image for Foundations of Programming: Object-Oriented Design
Foundations of Programming: Object-Oriented Design

47 video lessons · 55350 viewers

Simon Allardice
Author

 
Expand all | Collapse all
  1. 11m 35s
    1. Welcome
      1m 25s
    2. Who this course is for
      1m 15s
    3. What to expect from this course
      3m 6s
    4. Exploring object-oriented analysis, design, and development
      1m 41s
    5. Reviewing software development methodologies
      4m 8s
  2. 26m 14s
    1. Why we use object-orientation
      2m 42s
    2. What is an object?
      5m 22s
    3. What is a class?
      4m 43s
    4. What is abstraction?
      2m 45s
    5. What is encapsulation?
      3m 45s
    6. What is inheritance?
      3m 35s
    7. What is polymorphism?
      3m 22s
  3. 12m 16s
    1. Understanding the object-oriented analysis and design processes
      4m 13s
    2. Defining requirements
      6m 9s
    3. Introduction to the Unified Modeling Language (UML)
      1m 54s
  4. 23m 35s
    1. Understanding use cases
      6m 11s
    2. Identifying the actors
      4m 16s
    3. Identifying the scenarios
      5m 7s
    4. Diagramming use cases
      4m 18s
    5. Employing user stories
      3m 43s
  5. 16m 36s
    1. Creating a conceptual model
      1m 59s
    2. Identifying the classes
      2m 27s
    3. Identifying class relationships
      2m 38s
    4. Identifying class responsibilities
      6m 43s
    5. Using CRC cards
      2m 49s
  6. 22m 25s
    1. Creating class diagrams
      6m 11s
    2. Converting class diagrams to code
      4m 57s
    3. Exploring object lifetime
      5m 55s
    4. Using static or shared members
      5m 22s
  7. 19m 49s
    1. Identifying inheritance situations
      6m 49s
    2. Using inheritance
      2m 43s
    3. Using abstract classes
      2m 2s
    4. Using interfaces
      4m 20s
    5. Using aggregation and composition
      3m 55s
  8. 9m 23s
    1. Creating sequence diagrams
      5m 18s
    2. Working with advanced UML diagrams
      2m 3s
    3. Using UML tools
      2m 2s
  9. 10m 39s
    1. Introduction to design patterns
      2m 40s
    2. Example: the singleton pattern
      4m 53s
    3. Example: the memento pattern
      3m 6s
  10. 21m 47s
    1. Introduction to object-oriented design principles
      2m 50s
    2. Exploring general development principles
      3m 55s
    3. Introduction to SOLID principles
      6m 43s
    4. Introduction to GRASP principles
      8m 19s
  11. 7m 1s
    1. Reviewing feature support across different object-oriented languages
      3m 50s
    2. Additional resources
      2m 27s
    3. Goodbye
      44s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ .

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Foundations of Programming: Object-Oriented Design.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member ?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferences from the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Learn more, save more. Upgrade today!

Get our Annual Premium Membership at our best savings yet.

Upgrade to our Annual Premium Membership today and get even more value from your lynda.com subscription:

“In a way, I feel like you are rooting for me. Like you are really invested in my experience, and want me to get as much out of these courses as possible this is the best place to start on your journey to learning new material.”— Nadine H.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.