ISYS 200 Requirements Analysis

ISYS 200Requirements Analysis

Requirements Analysis • Determining the requirements for the system in detail • Systems analyst gathers data from client • Organizes the data • Interprets it to come up with a set of requirements for the new system • Result is a requirements document

Requirements Analysis • What are we trying to learn? • Remember Analysis = Understanding! • Understand the problem from the user's perspective • Organize the information in order to • design a solution • communicate your understanding • determine what you don't know

Requirements Analysis • There is information I am unaware of and I don't understand (realize) I am unaware of it For all project requirements information: There is information I am unaware of but I understand I am unaware of it There is information I am aware of but I don't understand it There is information I am aware of and I understand the information

Requirements Analysis • What information do we want to be aware of? • All of it • What information do we need to understand? • what is necessary to design and implement a satisfactory solution • avoid endless analysis!

System Development Information • IPSOC • (Input, Processing, Storage, Output, Controls) • Functionality • Structured Techniques • Separate into Data and Processing • Required Qualities • What are the requirements other than functionality? • Other items • Anything else that fits no where else?

Developing Data and Processing Information • Separate the user information into two groups • Data: things nouns • Processing: actions verbs

Processing Lists • Four groups of information • What are the activities that happen at this organization? • What things must happen that are part of this project? An activity is a major event at the organization • What are the major trigger events? • What causes the activity above to occur? • What processes are triggered by these events? • What particular internal processes begin when the trigger event occurs? A group of processes form an activity • After placing all the relevant processes under the trigger event, what do we want to call each activity? • Each process group is given a name.

Data list • What data is acted on or created by the processes previously described? • Create a list of this data • Can we group this data logically together into an entity? • Make a tentative data grouping • Entity: thing in the user's environment

Example • See • http://www.leitner.org/courses/du/isys200-0102/dfdexample.pdf • pages 3-4 through 3-8

What is Quality? • Quality is fitness for use • Quality is compliance to a standard • Quality is a degree of excellence • Quality means meeting a requirement

System Qualities • Stakeholder Visible • Functionality • What features must it have (take from scope)? • Usability • How easy to use must it be? • Robustness • Does it need to handle unusual situations? • Reliability • What amount of failures or problems are acceptable? • Performance • How good must it's performance be? • Efficiency • How efficient must it be in use of resources? • Understandability • How much do users need to know how it works?

System Qualities • “Under the hood” - Developer visible • Reusability • Do we need to be able to reuse parts of the system elsewhere? • Maintainability • Does it need to be changeable? • Portability • Does it need to operate in other h/w, s/w environments? • Interoperability • Does it need to communicate with other systems? • Testability • What testing is required?

Other Items • Your last question during analysis: • Is there anything we have missed? Anything else we need to talk about and deal with in this project? • Point: Don't lose information simply because it doesn't fit anywhere. Record it!

What Are the Sources of Information? • Documents • People • Experience

Data Gathering Methods • Sampling documents • Interviews • Questionnaires • Observations

Sampling Documents • Normally you cannot (and don’t want to) look at all documents • Sampling is systematically selecting representative elements of a population • Analyst usually samples: • Inputs to the system, e.g., data entry forms, data feeds from other systems • Outputs from the system, e.g., data, reports

Sampling • Gather examples of all the documents and determine what they contain, how they are used • Then decide • Which documents to sample • Over what time period • Sample procedure • Sample size

Sample Procedure • Sample by convenience – sample whatever is easily at hand • Unreliable, not based on probability • Simple random sample – number all elements of the population and then select using a random number generator • Don’t use every nth element • Stratified sample – identifying subpopulations and sampling randomly within them • E.g. strata could be managers, engineers, technicians

Interviews • Use to find out opinions and attitudes as well as facts • How the organization works (organizational culture) • Goals of the organization and how things are going • Feelings about the current system, major concerns • How things are really done • Attitudes toward project

Interview Planning • Read documents so you know about the organization and the information system(s) • Set interview objectives: what you want to learn • Choose people to interview • Set up interviews • Decide on interview type and prepare questions

Who to Interview? • People at all levels who will use or be affected by the system – balanced perspective • Management • Operators of the system • People who supply input to the system • People who use output of the system

How to interview • Listening is most important! • Be an active listener -- engage fully! • Reinforce your understanding by describing back to the user your understanding of what he or she has said • Interviewing is very hard work! • If you are finding it easy you are not doing it right!

Interview Type • Structured interview: all questions are planned • Closed questions that call for a specific answer • Example: How many transactions do you handle per hour? • Bipolar question call for a yes/no answer • Example: Do you use the company intranet? • Advantages: quick to carry out, easy to summarize results, don’t get off track • Disadvantages: Miss important insights, boring

Interview Type • Semi-structured interview: questions and their order may be modified on-the-fly • Open-ended questions • Interviewee can respond as he/she wishes • Examples: Does the benefits system give you the information you need? Why? (probe) • Advantages: more detail and insights, more interesting • Disadvantages: getting off track, too much irrelevant detail, too much time

Carrying Out the Interview • Pyramid and funnel structures for interview • Two interviewers • Taking notes • Audio and video taping

Interview Bias • Motivation of interviewees • Social desirability bias • Self-presentation bias • Plausibility bias

Questionnaires • Also known as surveys • Use to find out attitudes, beliefs, behavior, characteristics of members of organization • Can survey many people as follow-up to interview, contacting more people • Can also survey first, then use interviews to follow-up on interesting results in detail

Question Type • Closed questions • All of the possible responses listed • Example: How many times do you use the system per week (circle one): 0-2 3-5 5-10 over 10 • Advantages: easy to analyze, easy for respondents to fill out • Disadvantage: does not give rich insights, hard to write questions

Question Type • Open questions • Questions that allow the respondent to decide what and how much to say • Example: Are there ways in which the current system fails to meet your needs? • Advantages: allows systems analyst to explore situation, able to gain insights, • Disadvantage: hard to analyze the responses, time-consuming and difficult for respondent

Writing Questions • Clear, specific, and unambiguous • Use the language of the respondents • Correct reading level • Eliminate biases • Pilot the questions

Measurement Scales • Four measurement scales • Nominal – classify • Ordinal – rank • Interval – numbered scale with equal intervals between numbers • Ratio – numbered scale with equal intervals between numbers and an absolute zero

Measurement Scales • Four measurement scales • Nominal – classify • What is your major? • IS&T • Computer science • Engineering • Other • Ordinal – classification with rank ordering • Which is your preferred college: • Penn State • Drexel • Rutgers • Temple

Measurement Scales • Interval – numbered scale with equal intervals between numbers • What is your level of satisfaction with your education at Drexel? • Low Medium High • 1 2 3 • Ratio – numbered scale with equal intervals between numbers and an absolute zero • How many hours do you study per day? • 0 1-2 3-4 5-6 Over 6

Observations • Used to gain information not available through other methods • Also can be used to confirm information gained through other methods • Two methods are: • Event sampling • Time sampling

Time Sampling • Observe during specific time periods, e.g. four random 15-minute periods every day for 10 days • Advantages: • Lets you see common activities • Random selection of time periods avoids bias • Disadvantage: • You do not see the person during long blocks of time • You do not necessarily see the person during important events

Event Sampling • Observe during specific events in their entirety • Advantages: • Lets you see important activities • Lets you see how the activity evolves over time • Disadvantage: • Biased against seeing common, everyday activities • Observer may spend more time

Recording Observations • Categorizing behavior • Behaviors are listed on a form • Observer enters the number of times the behaviors are observed • Do this for each observation period • Can also include what information sources a person uses

Use of Experience • You will have certain insights into the project as you analyze • Do not assume you are correct • Treat your insights as hypotheses to be proven! • Information from users overrides your ideas!

ISYS 200 Requirements Analysis