Applied Software Project Management Chapter 6 Requirements Modified

Applied Software Project Management Chapter 6: Requirements [Modified version of Stellman and Greene’s Chapter 6 slides. Adapted for class use only in the CS 709 B course at UNR, Spring 2012] http: //www. stellman-greene. com 1 Andrew Stellman & Jennifer Greene

Applied Software Project Management Software Requirements Software requirements are documentation that completely describes the behavior that is required of the software-before the software is designed, built and tested w Requirements analysts (or business analysts) build software requirements specifications through requirements elicitation. • Interviews with the users, stakeholders and anyone else whose perspective needs to be taken into account during the design, development and testing of the software • Observation of the users at work • Distribution of discussion summaries to verify the data gathered in interviews http: //www. stellman-greene. com 2 Andrew Stellman & Jennifer Greene

Applied Software Project Management Interviews Examples of leading questions in interviews: • • • Why is the software being built? What benefits? What problems need to be addressed? Who will use the software? How often? Who will support the software? In what environment will the software be used? What are the known constraints? What inputs and outputs? Are there workarounds? Is there anything that I missed? Anything else that I should know? Are out there any potential limitations or problems? http: //www. stellman-greene. com 3 Andrew Stellman & Jennifer Greene

Applied Software Project Management Discussion Summary A requirements analyst can use a discussion summary to summarize information gathered during elicitation and validate it through a review Notes gathered during the elicitation should fit into the discussion summary template The discussion summary outline can serve as a guide for a novice requirements analyst in leading interviews and meetings http: //www. stellman-greene. com 4 Discussion Summary outline 1. Project background a) b) c) 2. Perspectives a) b) 3. Who will use the system? Who can provide input about the system? Project Objectives a) b) c) d) 4. 5. 6. 7. Purpose of project Scope of project Other background information Known business rules System information and/or diagrams Assumptions and dependencies Design and implementation constraints Risks Known future enhancements References Open, unresolved or TBD issues Andrew Stellman & Jennifer Greene

Applied Software Project Management Use Cases A use case is a description of a specific interaction that a user may have with the system Use cases are deceptively simple tools for describing the functionality of the software w Use cases do not describe any internal workings of the software, nor do they explain how that software will be implemented w They simply show the steps that the user follows to use the software to do his work w All of the ways that the users interact with the software can be described in this manner http: //www. stellman-greene. com 5 Andrew Stellman & Jennifer Greene

Applied Software Project Management Use Cases Use case template 1. 2. 3. 4. 5. 6. 7. http: //www. stellman-greene. com Summary Rationale Users Preconditions Basic course of events Alternative paths Postconditions 6 Andrew Stellman & Jennifer Greene

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Applied Software Project Management Use Cases Use case development script (major steps) 1. Identify the basic set of use cases 2. Add a rationale and summary to each case. Identify users. Create a master list of user categories. Where possible, add pre- and post-conditions. 3. Define basic course events and alternative paths for each use case 4. Very each use case, ensuring all paths make sense and are correct http: //www. stellman-greene. com 8 Andrew Stellman & Jennifer Greene

Applied Software Project Management Functional Requirements Functional requirements define the outward behavior required of the software project w The goal of the requirement is to communicate the needed behavior in as clear and unambiguous a manner as possible w The behavior in the requirement can contain lists, bullets, equations, pictures, references to external documents, and any other material that will help the reader understand what needs to be implemented http: //www. stellman-greene. com 9 Andrew Stellman & Jennifer Greene

Applied Software Project Management Functional requirements example http: //www. stellman-greene. com 10 Andrew Stellman & Jennifer Greene

Applied Software Project Management Nonfunctional Requirements Nonfunctional requirements define characteristics of the software which do not change its behavior w Users have implicit expectations about how well the software will work w These characteristics include how easy the software is to use, how quickly it executes, how reliable it is, and how well it behaves when unexpected conditions arise w The nonfunctional requirements define these aspects about the system. • The nonfunctional requirements are sometimes referred to as “non-behavioral requirements” or “software quality attributes” http: //www. stellman-greene. com 11 Andrew Stellman & Jennifer Greene

Applied Software Project Management Nonfunctional Requirements Categories of non-functional requirements • • • Availability Efficiency Flexibility Portability Integrity/Security Performance Reliability Reusability Robustness Scalability Usability http: //www. stellman-greene. com 12 Andrew Stellman & Jennifer Greene

Applied Software Project Management Nonfunctional Requirements Nonfunctional requirements example http: //www. stellman-greene. com 13 Andrew Stellman & Jennifer Greene

Applied Software Project Management Software Requirements Specification The software requirements specification (SRS) represents a complete description of the behavior of the software to be developed. The SRS includes: w A set of use cases that describe all of the interactions that the users will have with the software w All functional requirements necessary to define the internal workings of the software: calculations, technical details, data manipulation and processing, and other specific functionality that shows how the use cases are to be satisfied w Nonfunctional requirements, which impose constraints on the design or implementation (such as performance requirements, quality standards or design constraints) http: //www. stellman-greene. com 14 Andrew Stellman & Jennifer Greene

Applied Software Project Management Software Requirements Specification SRS Outline 1. Introduction - 2. 3. 4. 5. http: //www. stellman-greene. com Purpose Scope System overview References Definitions Use cases Functional requirements Nonfunctional requirements 15 Andrew Stellman & Jennifer Greene

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Applied Software Project Management SRS Inspection Checklist When done, the SRS document should be checked for: • • • Completeness Feasibility Modifiability Use case clarity Use case level of detail Use case testability Requirements clarity Requirements completeness Requirements consistency Requirements level of details http: //www. stellman-greene. com 17 Andrew Stellman & Jennifer Greene

Applied Software Project Management Requirements vs. Design Many people have difficulty understanding the difference between scope, requirements and design w The scope demonstrates the needs of the organization, and is documented in a vision and scope document w Requirements document the behavior of the software that will satisfy those needs w Design shows how those requirements will be implemented technically http: //www. stellman-greene. com 18 Andrew Stellman & Jennifer Greene

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Applied Software Project Management Change Control Change control is a method for implementing only those changes that are worth pursuing, and for preventing unnecessary or overly costly changes from derailing the project w Change control is an agreement between the project team and the managers that are responsible for decision-making on the project to evaluate the impact of a change before implementing it w Many changes that initially sound like good ideas will get thrown out once the true cost of the change is known http: //www. stellman-greene. com 20 Andrew Stellman & Jennifer Greene

Applied Software Project Management Change Control A change control board (CCB) is made up of the decision-makers, project manager, stakeholder or user representatives, and selected team members w The CCB analyzes the impact of all requested changes to the software and has the authority to approve or deny any change requests once development is underway w Before the project begins, the list of CCB members should be written down and agreed upon, and each CCB member should understand why the change control process is needed and what their role will be in it http: //www. stellman-greene. com 21 Andrew Stellman & Jennifer Greene

Applied Software Project Management Change Control Whenever a change is needed, the CCB follows the change control process to evaluate the change: w The potential benefit of the change is written down, and the project manager works with the team to estimate the potential impact that the change will have on the project w If the benefit of the change is worth the cost, the project manager updates the plan to reflect the new estimates. Otherwise, the change is thrown out and the team continues with the original plan. w The CCB either accepts or rejects the change http: //www. stellman-greene. com 22 Andrew Stellman & Jennifer Greene

Applied Software Project Management Problems with Software Requirements Iteration abuse w Iteration (or repetition) seems to be a good development practice, liked by many and with many benefits w However, if overdone, it in fact complicates the development and cannot substitute an initial good description of the required behavior of the software (it’s easier to change things on paper than in the code) Scope creep w Many project have ended in failure because poor change control w Through a series of apparently small and innocuous changes the scope of the projects drifts away from its original version http: //www. stellman-greene. com 23 Andrew Stellman & Jennifer Greene