The Software DevelopmentLife Cycle: An Overview

Presented by

Maxwell Drewand

Dan Kaiser

Southwest State University Computer Science Program

Last Time

Project Management Concepts

The Schwan’s Information Services

Deliverables Guide

Project Management Techniques

Project Management in MSF

Project Management in RUP

Session 3: Agenda

The Requirements Process

Schwan’s Requirements Phase

MSF Requirements

RUP Requirements

Requirements

Requirement: a feature of the system or a description of something the system is capable of doing in order to fulfill the system’s purpose

Three kinds of requirements: those that absolutely must be met those that are highly desirable but not necessary those that are possible but could be eliminated

Purpose of Requirements To establish and maintain agreement with the customers and other

stakeholders on what the system should do.

To provide system developers with a better understanding of the system requirements.

To define the boundaries of (delimit) the system.

To provide a basis for planning the technical contents of iterations.

To provide a basis for estimating cost and time to develop the system.

To define a user-interface for the system, focusing on the needs and goals of the users.

The Requirements Document The requirements document is the official

statement of what is required of the system developers

Should include both a definition and a specification of requirements

It is NOT a design document. As far as possible, it should set out WHAT the system should do rather than HOW it should do it

Requirements

Requirements definition A statement in natural language plus diagrams of the

services the system provides and its operational constraints. Written for customers

Requirements specification A structured document setting out detailed descriptions

of the system services. Written as a contract between client and contractor

Software specification A detailed software description which can serve as a

basis for a design or implementation. Written for developers

1. The software must provide a means of representing and1. accessing external files created by other tools.1.1 The user should be provided with facilities to define the type of1.2 external files.1.2 Each external file type may have an associated tool which may be1.2 applied to the file.1.3 Each external file type may be represented as a specific icon on1.2 the user’s display.1.4 Facilities should be provided for the icon representing an1.2 external file type to be defined by the user.1.5 When a user selects an icon representing an external file, the1.2 effect of that selection is to apply the tool associated with the type of1.2 the external file to the file represented by the selected icon.

Requirements definitionRequirements specification

Functional vs. non-functional requirements

Functional: describes an interaction between the system and its environment

Examples: System shall

communicate with external system X.

What conditions must be met for a message to be sent

Non-functional: describes a restriction or constraint that limits our choices for constructing a solution

Examples: Paychecks distributed no

more than 4 hours after initial data are read.

System limits access to senior managers.

Types of requirements

Physical environment Interfaces Users and human factors Functionality Documentation Data Resources Security Quality assurance

Requirements ReadersClient managersSystem end-usersClient engineersContractor managersSystem architectsSystem end-usersClient engineersSystem architectsSoftware developersClient engineers (perhaps)System architectsSoftware developersRequirementsdefinitionRequirementsspecificationSoftwarespecification

Different PerspectivesHow developers see users How users see developers

Users don’t know what they want. Developers don’t understand operational needs.Users can’t articulate what they want. Developers place too much emphasis on

technicalities.Users have too many needs that are politicallymotivated.

Developers try to tell us how to do our jobs.

Users want everything right now. Developers can’t translate clearly-stated needs intoa successful system.

Users can’t prioritize needs. Developers say no all the time.

Users refuse to take responsibility for the system. Developers are always over budget.Users are unable to provide a usable statement ofneeds.

Developers are always late.

Users are not committed to system developmentprojects.

Developers ask users for time and effort, even to thedetriment of the users’ important primary duties.

Users are unwilling to compromise. Developers set unrealistic standards forrequirements definition.

Users can’t remain on schedule. Developers are unable to respond quickly tolegitimately changing needs.

Characteristics of requirements

Are they correct? Are they consistent? Are they complete? Are they realistic? Does each describe something the customer

needs? Are they verifiable? Are they traceable?

Requirements Engineering Process

Feasibility study Find out if the current user needs can be satisfied

given the available technology and budget? Requirements analysis

Find out what stakeholders require from the system Requirements definition

Define the requirements in a form understandable to the customer

Requirements specification Define the requirements in a detailed form for the

designer

RE Process and its DeliverablesFeasibilitystudyRequirementsanalysisRequirementsdefinitionRequirementsspecificationFeasibilityreport SystemmodelsDefinition ofrequirementsSpecification ofrequirementsRequirementsdocument

Discovering Requirements Prototyping

Throw Away Evolutionary

Both referred to as “rapid” prototyping

Use Cases Will be discussed later

Expressing Requirements

Formal Methods Axiomatic Definition Specification Grammars Mathematical Specifications

Recurrence Relations Petri Nets

Formal methods have not been generally accepted by developers

Data AbstractionSemester record

Semester typeSemester dateGrade-point averageCompleted hours

Semester type(Fall, Spring, Summer)

Address informationTelephone numberStreet addressCityStatePostal code

Student recordNameStudent numberAddress informationNumber of semesters{Semester record}

Abstract Class Relationships

Transition Diagram (UML)

Entity Relationship Modeling

Example ERD

Object-Oriented Specifications

Each entity in the system is an object. A method or operation is an action that can be

performed directly by the object or can happen to the object.

Encapsulation: the methods form a protective boundary around an object.

Class hierarchies of objects encourage inheritance.

Polymorphism: same method for different objects, each with different behavior

Multiple Inheritance

Choosing a Specification Technique

Applicability Implementability Testability/simulation Checkability Maintainability Modularity Level of abstraction

/expressibility Soundness

Verifiability Run-time safety Tools maturity Looseness Learning curve Technique maturity Data modeling Discipline

Requirements validation Concerned with demonstrating that the

requirements define the system that the customer really wants

Requirements error costs are high so validation is very important Fixing a requirements error after delivery may cost

up to 100 times the cost of fixing an implementation error

Prototyping is an important technique of requirements validation

Requirements checking

Validity. Does the system provide the functions which best support the customer’s needs?

Consistency. Are there any requirements conflicts?

Completeness. Are all functions required by the customer included?

Realism. Can the requirements be implemented given available budget and technology

Validation TechniquesTable 4.6. Requirements validation techniques.

Manual techniques ReadingManual cross-referencingInterviewsReviewsChecklistsManual models to check functions and relationshipsScenariosMathematical proofs

Automated techniques Automated cross-referencingAutomated models to enact functionsPrototypes

Questions?

Schwan’s Requirements Deliverables

Project Requirements Objective

The objective of the Project Requirements phase is to identify and document the business requirements for the project.  Business requirements define the vision for the completed project in terms that the customer and user can understand and should concentrate on the business processes rather than technical processes.

Business Specifications (210) Objective

The objective of the Business Specifications is to define the business rules and give a high level overview of the way the business processes are completed. The DBA’s may be involved at this stage.

Required:Projects

Optional:Support

Deliverable to:Systems DevelopmentCustomer (Optional)

Deliverables

Business Event ModelRetention: System

Business Event DocumentRetention: System

Functional Decomposition Diagram

Retention: System

Context Diagram Retention: System

Entity/Relationship Modeling (220) Objective

The objective of the Entity/Relationship Diagram is to define an Entity/ Relationship model and approve a Logical Data model with logical attributes (where database changes are needed). Cardinalities will be included to show the business flow and how the system potentially will work. DBA’s should be involved in this step.

Required:Projects

Optional:Support

Deliverable:

Entity/Relationship DiagramLogical Data Model

Deliverable to:

Systems DevelopmentCustomer (Optional)

Responsibility:Business Systems Planning

Input/Output Requirements (230) Objective

The objective of the Input/Output Requirements is to develop the initial input and output requirements with the customer’s input and then review with the customer.

Required: Projects

Optional: Support

Deliverable:

Input RequirementsOutput Requirements

Deliverable to:

Systems DevelopmentCustomer

Responsibility: Business Systems Planning

SAP Tie: 2.4

Prototyping (240) Objective

The objective of the prototyping is to have the customer see the system and be able to give suggestions and approve the potential layout of the system. This is the beginning of reviewing potential third party packages if this is an option.

Required: <None>

Optional: Projects, Support

Deliverable: Customer Approval (Walkthrough form?)

Deliverable to:

Systems DevelopmentCustomer

Responsibility: Joint Responsibility

SAP Tie: 2.3,2.5

Detailed Business Specifications (250)

Objective

The objective of the Detailed Business Specifications is to detail the high level Business specifications’ using a method such as business use cases.

Required: Projects

Optional: Support

Deliverable:

Technology ModelBusiness Use CasesBusiness Detail Process Documentation

Deliverable to:

Systems DevelopmentCustomer (Optional)

Responsibility: Business Systems Planning

SAP Tie: 2.4

Business Test Cases (260) Objective

The objective of the Business Test Cases is to have a written plan to confirm after creation that the system meets the business needs of the customer. This plan should include a list of functionality needed at the business level. Customers should help create the Business Test Cases.

Required: ProjectsSupport

Optional: <None>

Deliverable: Business Test Cases

Deliverable to:

Systems DevelopmentCustomer (Optional)

Responsibility: Business Systems Planning

SAP Tie: 2.4

Project Approval

Objective

The objective of the Project Approval phase is to make sure that everyone involved agrees on the requirements and that costs and estimates are reasonable.

Project Approval Steps IS Review Requirements Walkthrough Customer Review Development Review Project Estimation

Statement of Work Objective The objective of the Statement of Work is to estimate:

Project Design Phase Only <or> Project Design and Project Development Phase. The scope of this Statement of Work will be dependent on how large the project is and if Design would be better suited to it’s own Statement of Work. A project Plan should be created and approved with Systems Development before the SOW is signed.

Questions?