Transcript Data Requirements for the Amanda Model System
Bouwkundige Informatiesystemen ADMS 2004
UML part 1
Jan Dijkstra - 2 augustus 2004
Subjects
• Software Engineering • UML General • UML : Use Case Diagram • Exercise UCD • UML : Activity Diagram • Microsoft Visio • Task UML-part 1
Software Engineering
Sommerville, Ian (2001)
Software Engineering, 6 th edition
Ch.1-3, 5 http://www.software-engin.com
What is software engineering?
• Software engineering is an engineering discipline which is concerned with all aspects of software production • Software engineers should adopt a systematic and organised approach to their work and use appropriate tools and techniques depending on the problem to be solved, the development constraints and the resources available
What is the difference between software engineering and system engineering?
• System engineering is concerned with all aspects of computer-based systems development including hardware, software and process engineering. Software engineering is part of this process • System engineers are involved in system specification, architectural design, integration and deployment
What is software?
• Computer programs and associated documentation • Software products may be developed for a particular customer or may be developed for a general market
The software process
• A structured set of activities required to develop a software system • Generic activities in all software processes are: – Specification – Design – Validation – Evolution
Generic software process models
• The waterfall model – Separate and distinct phases of specification and development • Evolutionary development – Specification and development are interleaved
Waterfall model
Requirements definition System and software design Implementation and unit testing Integr ation and system testing Operation and maintenance
Waterfall model problems
• Inflexible partitioning of the project into distinct stages • This makes it difficult to respond to changing customer requirements • Therefore, this model is only appropriate when the requirements are well-understood
Evolutionary development
• Exploratory development – Objective is to work with customers and to evolve a final system from an initial outline specification. Should start with well-understood requirements • Throw-away prototyping – Objective is to understand the system requirements. Should start with poorly understood requirements
Outline description
Evolutionary development
Concurr ent activities Specification Initial version Development Intermediate versions Validation Final version
Evolutionary development
• Problems – Lack of process visibility – Systems are often poorly structured – Special skills (e.g. in languages for rapid prototyping) may be required • Applicability – For small or medium-size interactive systems – For parts of large systems (e.g. the user interface) – For short-lifetime systems
Incremental development
Define outline requirements Develop system increment Assign requirements to increments Design system architecture Valida te increment System incomplete Integrate increment Valida te system Final system
Software Requirements
• Descriptions and specifications of a system
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 in particular situations.
• Non-functional requirements • constraints on the services or functions offered by the system such as timing constraints, constraints on the development process, standards, etc.
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 be high-level statements of what the system should do but functional system requirements should describe the system services in detail
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 requirements • Requirements which are a consequence of organisational policies and procedures e.g. process standards used, implementation requirements, etc.
• External requirements • Requirements which arise from factors which are external to the system and its development process e.g. interoperability requirements, legislative requirements, etc.
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 system architecture may be designed to structure the requirements – The system may inter-operate with other systems that generate design requirements – The use of a specific design may be a domain requirement
UML General
Study Matter
• Books
Fowler & Scott: UML distilled 2nd ed
Fowler & Scott: UML beknopt
Booch, Rumbauch & Jacobson: The Unified Modeling Language – User Guide Sander Hoogendoorn: Pragmatisch modelleren met UML 2.0
Leffingwell & Widrig: Managing Sofdtware Requirements – a use case approach • Web www.omg.org
www.popkin.com
About UML
1 of 2 • UML is the successor to the wave of object oriented analysis and design (OOA&D) methods. The methods of Booch, Rumbaugh and Jacobson (de 3 amigo’s) are merged. UML represents the culmination of best practices in practical object oriented modelling.
• UML offers a standard way to write a system’s blueprints, including conceptual things such as business processes and system functions as well as database schemas.
About UML
2 of 2 • UML is a modelling language, a notation used to express and document designs. • UML proposes a standard for technical exchange of models and designs.
• UML also defines a “meta-model”, a diagram that defines the syntax of the UML notation
UML Model Views
• Use Case Modelling – Requirements • Use Case diagrams • Structural Modelling – Static structure diagrams • Class diagrams • Object diagrams • Behaviour Modelling – State diagrams – Interaction diagrams • Sequence diagrams • Collaboration diagrams – Activity diagrams • Implementation diagrams
UML: what we will cover
– Documenting the system’s behaviour from the user’s viewpoint, requirements capture
– Describing the type of objects in a system and the static relationships between them
– Describing the sequencing of activities with support for both conditional and parallel behaviour
UML steps
1. Examine the necessities of the information system use cases 2. Object-oriented domain analysis decomposition of the problem field in concepts, attributes and associations that may be of relevance to the information system
Use Case Modelling
Use Case Diagram Example
Use Case Modelling
• A use case is a modelling technique used to describe what a new system should do or what an existing system already does.
• System developers and customers/end-users discuss a use case model. In an iterative process, this lead to a requirement specification on which all agree.
• A use case diagram describes the interaction between a set of use cases and the actors involved in these use cases.
Use Case definition
• Fowler: A use case is a typical interaction that a user has with a system in order to achieve some goals.
A use case is a description of a set of sequence of actions, including variants, that a system performs to yield an observable result of value to an actor.
• Cockburn: A use case describes a system’s behavior.
Actor
• An actor is someone or something that interacts with the system. It is who or what uses the system. • An actor communicates with the system by sending and receiving messages. • An actor is a role that a user plays with respect to the system.
• Actors – what exists outside the system (Rumbaugh) [external “participants”/”roles”]
Use cases
• A use-case is a set of sequences of actions a system performs that yield an observable result of value to a particular actor.
• A use-case describes a requirement for the system, that is, what it should do, but not how it should do it.
• A use-case is a set of scenarios tied together by a common user goal.
Use Case Diagram Example
Example Date2date : Basic UCD
Ontleend aan Sander Hoogendoorn
Example Date2date : Secondary UCD Ontleend aan Sander Hoogendoorn
Scenario
A scenario is a sequence of steps describing an interaction between a user and a system.
– A scenario is an instance of a use-case.
– A scenario describes a possible interaction with the system.
Scenario Example
• Consider a Web-based on-line store, we might have a ‘Buy a Product’ scenario that would say this : The customer browses the catalogue and adds desired items to the shopping basket. When the customer describes the shipping and credit card information and confirms the sale. The system checks the authorization on the credit card and confirms he sale both immediately and with a follow-up mail.
Example of a Use Case Text
Example Date2date : use case text Ontleend aan Sander Hoogendoorn
Example Date2date : use case text with scenario’s Ontleend aan Sander Hoogendoorn
Name
Template of an Use Case Text Name used to refer to a use case.
Actors
All actors involved.
Preconditions Description Exceptions Result
Condition of the system at the start of the use case. A complete stepwise description of the interaction between system and actor(s). Special and/or unexpected exceptional cases. Condition of the system at the end of the use case.
Steps 1. Define the system boundaries 2. Define actors 3. Define use cases 4.
Define scenario’s 5. Describe each use case 6. Identify communal sub-cases
Use Case relationships
• Generalization • Include relation • Extend relation
Generalization • Generalization is used when there is one use case similar to another.
• Inheriting parent behaviour, adding and overriding with the child’s behaviour.
• Sub use case inherits behaviour and semantics from super use cases.
Use Case Diagram Example
Example Date2date : Generalization Ontleend aan Sander Hoogendoorn
Example Date2date : Include Ontleend aan Sander Hoogendoorn
Include / Uses
• Uses / Include : this relationship is used when there is a common chunck of behaviour across more than one use case.
• Base use case includes the functionality of included use case.
Use Case Diagram Example
Extend
• Extend : is similar to genralization but is used to add behaviour to the base use case at certain extension points.
• A use case is optionally extended by functionality of another use case.
Example Date2date : Extend Ontleend aan Sander Hoogendoorn
Relationships between use cases
Example Date2date : System boundary & Secondary actor Ontleend aan Sander Hoogendoorn
Short Summary
What is Use Case modeling?
• Use Case model: a view of a system that emphasizes the behavior as it appears to outside users. A use case model partitions system functionality into transactions(“use cases’) that are meaningful to users (‘actors’) • A Use Case Diagram visualizes a use case model.
Core Elements
Construct Description Syntax use case actor
A sequence of actions, inclu ding variants, that a system (or other entity) can perform, interacting with actors of the system. A coherent set of roles that users of use cases play when interacting with these use cases.
UseCaseName system boundary
Represents the boundary between the physical system and the actors who interact with the physical system.
ActorName
Construct
Core Relationships
Description Syntax association extend generalization
The participation of an actor in a use case. I.e., instance of an actor and instances of a use case communicate with each other. A relationship from an
extension
use case to a
base
use case, specifying how the behavior for the extension use case can be inserted into the behavior defined for the base use case.
A taxonomic relationship between a more general use case and a more specific use case. <
Construct
Core Relationships
Description Syntax Include (uses)
A relationship from a
base
use case to an
inclusion
use case, specifying how the behaviour for the inclusion use case is inserted into the behaviour defined for the base use case. <
Use Case Diagram
: Example
NS Ticket service
Destination • Define a use case diagram of ‘NS Ticket service’ • Describe an use case.
Take ticket
Use Case diagram ‘NS Ticket service’ Buy OV ticket «extends» «uses» Buy NS ticket Traveller Pay ticket
Use Case Actors Preconditions Description Extension Exceptions Result
Buy OV Ticket Traveller Traveller has a valid pass 1.
2.
3.
4.
5.
6.
7.
Ticket device expects destination code Traveller enters destination code Extension point: NS ticket Ticket device checks code and calculates the charge. Shows destination code & fare. Activates ticket machine for paying Traveller pays (use case: Pay ticket) Ticket device print and supplies ticket Traveller takes ticket Destination code = NS station.
3a. Ticket device expects ticket type 3b. Traveller enters Single/Return, Discount Y/N, Class Traveller interrupt the interaction or walk away Traveller enters an incorrect destination code Payment is not finished off successful Traveller has ticket. (NS can look forward to the payment)
Exercise UCD
Starting point is the MKW casus • Make a Use Case Diagram of the MKW system and describe the use cases with an use case text.