Презентация «Requirements Engineering»
Смотреть слайды в полном размере 
Вы можете ознакомиться с презентацией онлайн, просмотреть текст и слайды к ней, а также, в случае, если она вам подходит - скачать файл для редактирования или печати. Документ содержит 88 слайдов и доступен в формате ppt. Размер файла: 1.59 MB
Pic.1
Chapter 4 – Requirements Engineering
Pic.2
Topics covered Functional and non-functional requirements Requirements engineering processes Requirements elicitation Requirements specification Requirements validation Requirements change
Pic.3
Requirements engineering The process of establishing the services that acustomer requires from a system and the constraints under which it operates and is developed. The system requirements are the …
Pic.4
What is a requirement? It may range from a high-level abstract statement of a service or of a system constraint to a detailed mathematical functional specification. This is inevitable as requirements …
Pic.5
Requirements abstraction (Davis)
Pic.6
Types of requirement User requirements Statements in natural language plus diagrams of the services the system provides and its operational constraints. Written for customers. System requirements A …
Pic.7
User and system requirements
Pic.8
Readers of different types of requirements specification
Pic.9
System stakeholders Any person or organization who is affected by the system in some way and so who has a legitimate interest Stakeholder types End users System managers System owners External …
Pic.10
Stakeholders in the Mentcare system Patients whose information is recorded in the system. Doctors who are responsible for assessing and treating patients. Nurses who coordinate the consultations with …
Pic.11
Stakeholders in the Mentcare system A medical ethics manager who must ensure that the system meets current ethical guidelines for patient care. Health care managers who obtain management information …
Pic.12
Agile methods and requirements Many agile methods argue that producing detailed system requirements is a waste of time as requirements change so quickly. The requirements document is therefore always …
Pic.13
Functional and non-functional requirements
Pic.14
Functional and non-functional requirements Functional requirements Statements of services the system should provide, how the system should react to particular inputs and how the system should behave …
Pic.15
Functional requirements Describe functionality or system services. Depend on the type of software, expected users and the type of system where the software is used. Functional user requirements may …
Pic.16
Mentcare system: functional requirements A user shall be able to search the appointments lists for all clinics. The system shall generate each day, for each clinic, a list of patients who are …
Pic.17
Requirements imprecision Problems arise when functional requirements are not precisely stated. Ambiguous requirements may be interpreted in different ways by developers and users. Consider the term …
Pic.18
Requirements completeness and consistency In principle, requirements should be both complete and consistent. Complete They should include descriptions of all facilities required. Consistent There …
Pic.19
Non-functional requirements These define system properties and constraints e. g. reliability, response time and storage requirements. Constraints are I/O device capability, system representations, …
Pic.20
Types of nonfunctional requirement
Pic.21
Non-functional requirements implementation Non-functional requirements may affect the overall architecture of a system rather than the individual components. For example, to ensure that performance …
Pic.22
Non-functional classifications Product requirements Requirements which specify that the delivered product must behave in a particular way e. g. execution speed, reliability, etc. Organisational …
Pic.23
Examples of nonfunctional requirements in the Mentcare system
Pic.24
Goals and requirements Non-functional requirements may be very difficult to state precisely and imprecise requirements may be difficult to verify. Goal A general intention of the user such as ease of …
Pic.25
Usability requirements The system should be easy to use by medical staff and should be organized in such a way that user errors are minimized. (Goal) Medical staff shall be able to use all the system …
Pic.26
Metrics for specifying nonfunctional requirements
Pic.27
Requirements engineering processes
Pic.28
Requirements engineering processes The processes used for RE vary widely depending on the application domain, the people involved and the organisation developing the requirements. However, there are …
Pic.29
A spiral view of the requirements engineering process
Pic.30
Requirements elicitation
Pic.31
Requirements elicitation and analysis Sometimes called requirements elicitation or requirements discovery. Involves technical staff working with customers to find out about the application domain, …
Pic.32
Requirements elicitation
Pic.33
Requirements elicitation Software engineers work with a range of system stakeholders to find out about the application domain, the services that the system should provide, the required system …
Pic.34
Problems of requirements elicitation Stakeholders don’t know what they really want. Stakeholders express requirements in their own terms. Different stakeholders may have conflicting requirements. …
Pic.35
The requirements elicitation and analysis process
Pic.36
Process activities Requirements discovery Interacting with stakeholders to discover their requirements. Domain requirements are also discovered at this stage. Requirements classification and …
Pic.37
Requirements discovery The process of gathering information about the required and existing systems and distilling the user and system requirements from this information. Interaction is with system …
Pic.38
Interviewing Formal or informal interviews with stakeholders are part of most RE processes. Types of interview Closed interviews based on pre-determined list of questions Open interviews where …
Pic.39
Interviews in practice Normally a mix of closed and open-ended interviewing. Interviews are good for getting an overall understanding of what stakeholders do and how they might interact with the …
Pic.40
Problems with interviews Application specialists may use language to describe their work that isn’t easy for the requirements engineer to understand. Interviews are not good for understanding domain …
Pic.41
Ethnography A social scientist spends a considerable time observing and analysing how people actually work. People do not have to explain or articulate their work. Social and organisational factors …
Pic.42
Scope of ethnography Requirements that are derived from the way that people actually work rather than the way I which process definitions suggest that they ought to work. Requirements that are …
Pic.43
Focused ethnography Developed in a project studying the air traffic control process Combines ethnography with prototyping Prototype development results in unanswered questions which focus the …
Pic.44
Ethnography and prototyping for requirements analysis
Pic.45
Stories and scenarios Scenarios and user stories are real-life examples of how a system can be used. Stories and scenarios are a description of how a system may be used for a particular task. Because …
Pic.46
Photo sharing in the classroom (iLearn) Jack is a primary school teacher in Ullapool (a village in northern Scotland). He has decided that a class project should be focused around the fishing …
Pic.47
Scenarios A structured form of user story Scenarios should include A description of the starting situation; A description of the normal flow of events; A description of what can go wrong; Information …
Pic.48
Uploading photos iLearn) Initial assumption: A user or a group of users have one or more digital photographs to be uploaded to the picture sharing site. These are saved on either a tablet or laptop …
Pic.49
Uploading photos What can go wrong: No moderator is associated with the selected project. An email is automatically generated to the school administrator asking them to nominate a project moderator. …
Pic.50
Requirements specification
Pic.51
Requirements specification The process of writing donw the user and system requirements in a requirements document. User requirements have to be understandable by end-users and customers who do not …
Pic.52
Ways of writing a system requirements specification
Pic.53
Requirements and design In principle, requirements should state what the system should do and the design should describe how it does this. In practice, requirements and design are inseparable A …
Pic.54
Natural language specification Requirements are written as natural language sentences supplemented by diagrams and tables. Used for writing requirements because it is expressive, intuitive and …
Pic.55
Guidelines for writing requirements Invent a standard format and use it for all requirements. Use language in a consistent way. Use shall for mandatory requirements, should for desirable …
Pic.56
Problems with natural language Lack of clarity Precision is difficult without making the document difficult to read. Requirements confusion Functional and non-functional requirements tend to be …
Pic.57
Example requirements for the insulin pump software system
Pic.58
Structured specifications An approach to writing requirements where the freedom of the requirements writer is limited and requirements are written in a standard way. This works well for some types of …
Pic.59
Form-based specifications Definition of the function or entity. Description of inputs and where they come from. Description of outputs and where they go to. Information about the information needed …
Pic.60
A structured specification of a requirement for an insulin pump
Pic.61
A structured specification of a requirement for an insulin pump
Pic.62
Tabular specification Used to supplement natural language. Particularly useful when you have to define a number of possible alternative courses of action. For example, the insulin pump systems bases …
Pic.63
Tabular specification of computation for an insulin pump
Pic.64
Use cases Use-cases are a kind of scenario that are included in the UML. Use cases identify the actors in an interaction and which describe the interaction itself. A set of use cases should describe …
Pic.65
Use cases for the Mentcare system
Pic.66
The software requirements document The software requirements document is the official statement of what is required of the system developers. Should include both a definition of user requirements and …
Pic.67
Users of a requirements document
Pic.68
Requirements document variability Information in requirements document depends on type of system and the approach to development used. Systems developed incrementally will, typically, have less …
Pic.69
The structure of a requirements document
Pic.70
The structure of a requirements document
Pic.71
Requirements validation
Pic.72
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 …
Pic.73
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 …
Pic.74
Requirements validation techniques Requirements reviews Systematic manual analysis of the requirements. Prototyping Using an executable model of the system to check requirements. Covered in Chapter …
Pic.75
Requirements reviews Regular reviews should be held while the requirements definition is being formulated. Both client and contractor staff should be involved in reviews. Reviews may be formal (with …
Pic.76
Review checks Verifiability Is the requirement realistically testable? Comprehensibility Is the requirement properly understood? Traceability Is the origin of the requirement clearly stated? …
Pic.77
Requirements change
Pic.78
Changing requirements The business and technical environment of the system always changes after installation. New hardware may be introduced, it may be necessary to interface the system with other …
Pic.79
Changing requirements Large systems usually have a diverse user community, with many users having different requirements and priorities that may be conflicting or contradictory. The final system …
Pic.80
Requirements evolution
Pic.81
Requirements management Requirements management is the process of managing changing requirements during the requirements engineering process and system development. New requirements emerge as a …
Pic.82
Requirements management planning Establishes the level of requirements management detail that is required. Requirements management decisions: Requirements identification Each requirement must be …
Pic.83
Requirements change management Deciding if a requirements change should be accepted Problem analysis and change specification During this stage, the problem or the change proposal is analyzed to …
Pic.84
Requirements change management
Pic.85
Key points Requirements for a software system set out what the system should do and define constraints on its operation and implementation. Functional requirements are statements of the services that …
Pic.86
Key points The requirements engineering process is an iterative process that includes requirements elicitation, specification and validation. Requirements elicitation is an iterative process that can …
Pic.87
Key points Requirements specification is the process of formally documenting the user and system requirements and creating a software requirements document. The software requirements document is an …
Pic.88
Key points Requirements validation is the process of checking the requirements for validity, consistency, completeness, realism and verifiability. Business, organizational and technical changes …
Если вам понравился сайт и размещенные на нем материалы, пожалуйста, не забывайте поделиться этой страничкой в социальных сетях и с друзьями! Спасибо!
