Question From Past Final Exams

[ finals.html ]

Session 19 Questions

What factors are overlooked most in visions and cost-benefit models

I have no real evidence of which factoprs are missed.

My personal guess is the human factors are a commonly ignored and the technology over-emphasized.

There is also a tendency to throw a computer at the problem -- without analysing what software, maintenance, backup, training, etc. is needed.

Can you give an example of a modern thin client

Cell phone (medium cost).

What is the difference between flow charts and DFDs


Table

DFD	Flowchart
Data storage	Actions
Communication	Sequence of Control
Continuous	START,STOP
Flows divide	Decisions make choices
Implicitly Parallel	Explicit Fork/Join Parallelism


(Close Table)


How do the deployed artifacts realise the necessary data and processes

The word realise is pure UML jargon. We say A realizes B when A makes abstract B real. For example, you may need to store information about Students in your system, and this need is realized by a MySQL data base that has a Student table in it deployed on a Linux data base server. Processes become real as executable programs and libraries or scripts.

So there are many different ways that an artifact can fulfill a requirement. this is called 'realizing' it.

Are DFDs the most commonly used in describing a system

Yes.

Does RAD use Frameworks, and if so which ones

The essence of RAD is the technology to describe common types of processes quickly and easily. A very high level language can achieve this without the need of a framework. Thus Visual Basic used to give a working prototype very quickly. However these days, a Windows prototype will need to use the .Net framework on top of VB.

Sometimes a language has a framework that makes prototyping much easier -- Ruby on Rails is an example. Ruby is an elegant language. Rails is a framework that simplifies web development of simple web sites.

As a rule a framework needs as much time to learn as a programming language. It may be quicker -- since RAD prototypes are throw-away prototypes -- to just use the language without the framework.

What is the worst functional requirement you've encountered

In my programming, all requirements prior to 1978 were associated with a bad feeling in my stomach, then I started to learn methods that gave me a place to start. Here are two that I never even attempted and have occassional nightmares about:

1. Simulate a beer barrel bouncing.
2. Given a knitting pattern draw the fished garment.



There are also ones that I have attempted, failed to solve, and still wake up in the middle of the night trying to solve them. They are all simple to state and addictive. So I'm keeping them to my self.

Can you go over third normal Form

A data base is in third normal form or 3NF if in each table the prime key determines the rest of the data in the table, and the whole key is needed to determine the data, and if no other dependencies are hidden between columns in the table.

How do you figure out how much programming is going to be needed in a

project This is called "estimation". It is NOT easy. Here are some hints:

1. Base your estimates on the historical data you've collected about your team and its projects.
2. Break down the project into many small activities and estimate each step separately.
3. Use CPM to work out the best schedule and the minimum time needed.
4. Express estimates in terms of the chance of finishing before that time, not as certain completion dates. When will you be 90% certain the job will be done.
5. Use the PERT formula:
6. expected = (best + 2*most_likely + worst)/6.
7. Get your people involved in the process.
8. Avoid confusing targets with estimates.
9. All for the mistakes with a safety factor.



Can you talk about system development environments

We are a little short of time and the question is ambiguous.

First there is the organizational environment -- how things are done, who does them, and how things are paid for....

Then there are the tools that can be used -- especially the integrated Development Environments (IDEs) that combine editor, debugger, compiler, testing, and various libraries and frameworks into a single tool.

With each meaning there are a lot of alternative forms...

How hard is CS375

Have a look at the [ ../cs375/ ] website that has grade distributions, book, work schedules, etc.

It is designed to be a 4 unit class covering a method of going from requirements to a good object-oriented design. And it seems to take the standard amount of prep and homework.

When faced with a design problem what steps should be taken in designing the system architecture

You should have a list of processes/use cases plus all the data formats and data base design.

Your task is to choose the hardware and its connections that will support the software that meets the requirements.

Doing this is something of a black art.... the best technique is to create a possible system architecture and evaluate it against the non-functional and functional requirements. Look for the non-functional requirements that are most broken and adjust the architecture so it meets them. For example -- you predict that the web server (cost $600) won't be able to provide the speed under expected load because its CPU will be at 100% .... so you recommend a dual core processor, or go to a set of web servers and a load ballancing... front end that distributes the request between them (and the cost goes up to $2,000)...

If you can't find a suitable improvement then you need to think outside the box. My favorite trick is to look for common factors in all my solutions and deliberately change them. Another is to systematically challenge each constraint and assumption...

Why must we normalize data

When I first heard of normalization and relational data bases (1973?) I thought they were an academic fad. Then I discovered that my students were using it in industry and had to change my opinions... not a fad but a practical necessity.




1. Data base management systems work when the data is normalized.
2. Other professionals will expect you to do it.
3. Because we said so.



Show the steps in a project and the techniques that can be used in that step

Bear in mind that each organization has its own scenario for analysis and design. But here is a not untypical project and the possible techniques
Table

Step	Techniques
Fact finding	system thinking, interviews, field trips, deployment, meetings, DFDs, scenarios, data samples,...
Problem Solving	THINK! DFDs, brainstorm, walkthrough, physical->logical->ideal->new physical, cybernetics, patterns...
Data Base Design	DFDs, ERDs, data samples, encoding alternatives, normalization, ...
Hardware Selection	Input, Output, connection alternatives, DFDs->deployments, systems architecture
Human-Computer Interfaces	HCI, interaction design, activity diagrams, look-and-feel design, metaphors, storyboards, HTML, CSS, ...
Software Development	DFDs, ERDs, Requirements, RAD, JAD, stories, use cases, rules, SQL, logic, mathematics, patterns
Installation & Training	DFDs, scenarios, stories, procedures, workshops, ...
Operation & Maintenance	documentation, help desk, monitor for problems...


(Close Table)


Do DFDs and ERDs get used in real life or do corporations forget them

YES! Both. You'll find that the big corporations have a the greatest tendency to overdo DFDs/ERDs/.... paperwork. The small young businesses that go agile -- stressing people, working code, face-to-face communication, and 3><5 cards.

What are some strategies to reduce response times in a system that

already exists It is, said Sherlock Holmes, "a capital mistake to theorize without data". In the systems world it is all to easy to spend time and money improving the wrong thing. Therefore it pays to take time to find the real problem ... the bottleneck or clog.

1. Monitor the system to get a precise diagnosis of the problem:
   • What happens and what does not happen?
   • When, Where, and How does it happen and not happen
2. One or more of the following should help, in decreasing order of likelihood
   
   1. Better bandwidth or reduced data flow.
   2. Improve the structure of the data.
   3. Get a better algorithm
   4. Upgrade a CPU or try a set of parallel CPUs
   
   



Can you please discuss the Critical Path Method CPM

I had planned to but the wind closed the campus... The notes [ c3.html ] are fairly extensive and the method is easy to understand and apply. If we have time in the last class I will demo an example.

Could you go over UML activity Diagrams

These are just flow charts with a modern notation. My notes [ r1.html ] are enough for this class. Just make sure you understand how to draw decisions, loops, and parallel branches.

. . . . . . . . . ( end of section Session 19 Questions) <<Contents | End>>

Session 20 Questions

What are high-level business requirements

These typically short sentences giving a very rough picture of what is needed: the view of the requirments from a great hieght

 		The system helps students register for a class.

  	The system will be user friendly.

Key symptom: you have to work hard to get a detailed specification of what is and is not needed in the system being designed.

What is the difference between a fish-eye and a level-1 DFD

The fish-eye is just the best way to show the process you are expanding as you expand a single level 0 process..

What is a fish-eye diagram

It shows a lot of detail in the middle surrounded with the connections to other systems. In a DFD there is a big central process box surrounded by the entities/stores/processes it communicate with plus a lot of internal process and stores inside.

How detailed should data dictionaries have to be

Very. If the data doesn't exist already you have to plan and document everything about each element and each record.

What will the main focus of the final

Comprehensive and high level.

What was the toughest system architecture diagram I've had to do

Those I tried to do before I learned to keep them very very simple.

Who had the most interesting project

I'm not sure and if I was sure I wouldn't say to the other groups.

Can I give the answer to the final

I could go over the answers to the ones I've published but they are not quite the ones I'll be using.

How often is the UML used

It is the dominant graphical notation. I don't have any figures of its usage however.

Business Rules

Business rules are rules governing the system that can not be easily expressed in ERDs, use cases, DFDs, etc. For example that you have to complete prerequisites before enrolling in a section, OR you must pay to reserve a DVD, or there is a special discount on Tuesday to seniors who have one of our credit cards.

There are many ways of writing them. I would suggest always writing the rule in simple English and then spelling it out in detail using one of the following:


1. tree diagram
2. decision table
3. function table
4. pseudocode
5. Symbolic logic
6. mathematics

Check out [ r1.html ] for more information.

In the mock final does "Input and Output Options" refer to input and out put devices

Yes.

Questions from last time

Is the real final going to in the same format as the mock final.

Yes.

When doing a presentation in the real world how big can the presentation get

In terms of the size of the audience, I've attended a presentation on an OS upgrade with 60 people in the audience. The typcal presentation to management is to a group of people in a conference room -- no more than 15 people. It depends on the number of stakeholders and decision makers. When calling a meeting you need to select the audience carefully, of course.

In terms of time: Humans loose focus after 20 minutes unless you change the pace or supply caffeine and sugar. Donuts and coffee help! So does involving the audience.

The ideal time depends on the type of presentation. Presentations to management should be shorter than presentations of technical ideas to engineers, for example. As a rule, technical people find meetings a waste of their time and so we have things like "stand up meetings" limitted to 15 minutes to share progress and blockages. I'm surprised that no data has apeared on the use of electronic meetings and presentations on software development.

Whatever: don't prepare a presentation until you know the audience, the place, and (of course) the content!

What is a deletion anomaly

A deletion anomaly occurs when the deletion of information about one entity in the data also deletes information about another entity.

For example if there is a data group

1. Course( **schedule_number, *course, instructor_name, instructor_office, ...)

   Then deleting the last course that contains a particular instructor also wipes out the data about the instructor.

   The cure is normalization.

   How do you determine which data groups are expanded in 3NF

   The steps are: The Key, The Whole Key, and Nothing but the Key.

   Given 2NF data then each data group will have a prime key and attributes that are determined by the whole of that key.

   Therefor look at data groups that are not in the key in 2NF and that have attributes that act as keys to other attributes. In other words there are non-key functional dependencies.

   For example:

2. Course( **schedule_number, *course, instructor_name, instructor_office, ...) has an attribute (instructor_name) that determines the value of another one (instructor_office). So you should split this out of Course:
3. Course( **schedule_number, *course, *instructor_name, ...)
4. Instructor( **instructor_name, instructor_office, ...)

   Notice that all the attributes in the 2NF Course that depend on instructor_name move out of Course and into the new group Instructor.

   Is Normalization on the final

   There will be questions about normalization -- but I don't have the space, and you don't have the time to normalize any realistic data.

   Can you give an example of an ERD

   I've just had to input some scores from a mock GRE examination. Each student answered 48 questions. Each answer is one of the letters A, B, C, D, or E. There are 2 dozen students. Here is an image of piece of the data

   

   The facts of interest are like this
   Student s answered a to question q.
   Student s has a name, ....
   Question q has a number, a correct answer, a topic, a text, ...

   Here is a list of entities:

5. Student, Answer, Question.

   Here are the functional dependencies between entities:

6. Each Answer is from a single Student, and
7. Each Answer is to a single Question.

   So, here is the ERD:

   

   I hope this helps!

   Can you give an example of the Critical Path Method -- CPM

   Suppose I need to prepare a final examination for a class. I have the following tasks that I must carry out:
   Table

   Activity	Previous	Time(hours)
   1. Review topics taught	-	1
   2. Write the questions	1	2
   3. Review and mark up	2	1
   4. Edit	3	1
   5. Generate and publish mock	2	1
   6. Print final	4	1

   
   (Close Table)
   

   Next step: draw UML activity diagram [ MakeFinal.png ] , then add durations [ MakeFinal2.png ] , then work out the earliest time transitions (arrows) can happen: [ MakeFinal3.png ] , then work out the latest times transitions can happen [ MakeFinal4.png ] , and finally high-light the critical path: [ MakeFinal5.png ] (Note use right click to pop these images into different windows).

. . . . . . . . . ( end of section Session 20 Questions) <<Contents | End>>

. . . . . . . . . ( end of section Review Questions) <<Contents | End>>

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