SE 555 Software Requirements & Specification Requirements Analysis

SE 555 Software Requirements & Specification Goals of Requirements Analysis Create requirements containing sufficient detail and of high enough quality to allow realistic project planning as well as successful design and implementation. Scrutinize requirements for errors, conflicts, omissions and boundaries.

SE 555 Software Requirements & Specification Requirements Analysis Practices Analyze feasibility Allocate requirements to subsystems Create prototypes where necessary Model the requirements Prioritize the requirements Define system boundaries and interfaces Create consistent data definitions

SE 555 Software Requirements & Specification Requirements Analysis Checklist Premature Design – Does the requirement include premature design or implementation information? Combined Requirements – Does the description of a requirement describe a single requirement or could it be broken down into several different requirements? Unnecessary Requirements – Is the requirement “gold plating”? That is, is the requirement a cosmetic addition to the system which is not really necessary. Use of Non-standard Components – Does the requirement mean that non-standard hardware or software must be used?

SE 555 Software Requirements & Specification Requirements Analysis Checklist – cont’d Conformance with Business Goals – Is the requirement consistent with the business goals defined in the introduction to the requirements document/ Requirements Ambiguity – Is the requirement ambiguous i.e. could it be read in different ways by different people? Requirements Realism – Is the requirement realistic given the technology which will be used to implement the system? Requirements Testability – Is the requirement testable? Is it stated in such a way that a test can be derived to show if the system meets the requirement?

SE 555 Software Requirements & Specification Requirements Analysis Artifacts System Boundaries – Context Diagram Requirements Modeling – Class Diagrams, Activity State Diagrams, Interaction Diagrams, Sequence Diagrams, Data Flow Diagrams, Entity-Relationship Diagrams Data Definition – Data Dictionary Requirements Priority – Prioritization Matrix Requirements Definition, Risk Mitigation, Feasibility – Prototypes

SE 555 Software Requirements & Specification Context Diagram - Purpose Highlights the boundary between the system and the outside world. Highlights the people, organizations, and outside systems that interact with the system under development. Special case of the data flow diagram.

SE 555 Software Requirements & Specification Context Diagram - Notation Process - Represents the proposed system Terminator - Represents the external entities Flow - Represents the in and out data flows

SE 555 Software Requirements & Specification Context Diagram - Example Credit Card Processing Customer Collection Company Corporate Accounting System Store Customer Service Application Bills Payment Transaction Payment Overdue Accounts Credit Account Summary

SE 555 Software Requirements & Specification Use-Case Analysis Use-case analysis is where the requirements meet object-orientation Recall: in the Unified Process, the use-case model is the primary artifact in the requirements model In use-case analysis, identify the classes which perform a use-case flow of events Distribute the use-case behavior to those classes Identifying the responsibility of the classes Develop use case realizations that model the collaborations between instances of the identified classes How the class instances work together to deliver the requirements The result is a first-draft, rough-cut of the system object model An abstraction of the design model; refined during design

SE 555 Software Requirements & Specification Use-Case Analysis - Steps Supplement the Use-Case Description For each use-case realization Find classes from use-case behavior Distribute use-case behavior to classes For each resulting analysis class Describe responsibilities Describe attributes and associations Qualify architectural analysis mechanisms Unify analysis classes Checkpoints

SE 555 Software Requirements & Specification Analysis Classes: A First Step Towards Executables Use-CasesAnalysis Classes Design Elements Source Code Executables Use-Case Analysis

SE 555 Software Requirements & Specification Data Flow Diagram - Purpose Provides a means for functional decomposition. Primary tool in analysis to model data transformation in the system.

SE 555 Software Requirements & Specification Data Flow Diagram - Notation Represents the external entities that the System communicates with Represents data flows Represents functions in the system (transforms Inputs into Outputs) Represents data stores (a collection of data at “rest”)

SE 555 Software Requirements & Specification DFD Example from Text

SE 555 Software Requirements & Specification Data Dictionary A repository that defines the data elements or attributes used in the system It is not the project glossary Makes it easy to find info about the data Avoids redundancy and maintenance issues, over being in various func. req. Have it as an appendix in your SRS (project)

SE 555 Software Requirements & Specification DD Notation Primary data element Where an element does not need or require further decomposition Defined with a comment * text * Data type, size, range of values etc. are presented. Composition: + Used to show multiple data items Optional items are enclosed in () Iteration: min:max {item} Used to show that mult instances of an item can appear Selection: [item | item] When a data element can be of a set of discrete values

SE 555 Software Requirements & Specification DD Examples Customer Name Phone Number

SE 555 Software Requirements & Specification DD Notation Entry comprised of: (and listed in alphabetical order) Name: its name Aliases: if it goes by another name as well Used in: the use cases it is present in, by id and name Description: the notation goes here Notes: any special notes about it

SE 555 Software Requirements & Specification Entity Relationship Diagram (ERD) - Purpose A graphical representation of the data layout of a system at a high level of abstraction. Defines data elements and their inter-relationships in the system.

SE 555 Software Requirements & Specification Entity Relationship Diagram - Text Example