internet software development putting it all together paul j krause

Internet Software Internet Software DevelopmentDevelopment

Putting it all togetherPutting it all together

Paul J KrausePaul J Krause

Software LifecycleSoftware Lifecycle

Customer Requirements

Functional Requirements

Design

Implementation

Unit Test

System Test

Acceptance Test

Customer RequirementsCustomer Requirements



Design

Implementation

Unit Test

System Test

Acceptance Test

Why Requirements?Why Requirements?“The firms improving their development speed at the fastest rate actually spend more elapsed time and more effort in the customer requirements stage of the project …. These firms spend significantly less time in the testing and integration stage of development.…”

“The firms improving their development speed at the fastest rate actually spend more elapsed time and more effort in the customer requirements stage of the project …. These firms spend significantly less time in the testing and integration stage of development.…”

Blackburn, Scudder, et al, in Improving Speed and Productivity of Software Development: A Global Survey of Software Developers (1996)

0%

5%

10%

15%

20%

Schedule Effort

Faster FirmsSlower Firms

Resources spent on Customer Requirements:

Tom on ‘Requirement’Tom on ‘Requirement’ Requirement: Requirement: Concept *026 November 8, 2001 22:16Concept *026 November 8, 2001 22:16

A requirement is a stakeholder-desired Target or A requirement is a stakeholder-desired Target or Constraint.Constraint.

Notes: Notes: 1. The constraints can apply to an engineering process, a design or an 1. The constraints can apply to an engineering process, a design or an

operational system.operational system. 2. A requirement is an input to a defined level of design process. 2. A requirement is an input to a defined level of design process. 3. Requirements give information to the designer about the necessary nature 3. Requirements give information to the designer about the necessary nature

of their design. of their design. 4. Consequently the design, specification or implementation, can be judged 4. Consequently the design, specification or implementation, can be judged

{Spec QC, review, test or in operation} in terms of how well it satisfies those {Spec QC, review, test or in operation} in terms of how well it satisfies those requirements.requirements.

INTRO

Requirement Specification.Requirement Specification. Requirement Specification. Concept *508. November 8, 2001 1604Requirement Specification. Concept *508. November 8, 2001 1604

A requirement specification is the A requirement specification is the readable expression of a requirement readable expression of a requirement and any requirement background.and any requirement background.

Related Concepts: Related Concepts: requirement *026 the future state or constraintrequirement *026 the future state or constraint specification *137 the readable specification *137 the readable artifactartifact background *507 additional information about the requirementbackground *507 additional information about the requirement

Analysis of dangerous common Analysis of dangerous common requirements practices.requirements practices.

Mixing real requirements with ‘designs’Mixing real requirements with ‘designs’ Failing to quantify competitive qualitiesFailing to quantify competitive qualities Failing to derive implied requirements from designsFailing to derive implied requirements from designs Failing to set requirements at appropriate levelFailing to set requirements at appropriate level Failing to include source informationFailing to include source information Failing to include priority informationFailing to include priority information Failing to specify all critical stakeholders requirementsFailing to specify all critical stakeholders requirements Failing to distinguish between wishes and their profitFailing to distinguish between wishes and their profit Failing to consider all limited resources as requirementsFailing to consider all limited resources as requirements Failure to update requirements evolutionarilyFailure to update requirements evolutionarily Failure to consider time, location and conditions with requirementsFailure to consider time, location and conditions with requirements Failure to plan a time series of quality levelsFailure to plan a time series of quality levels

Stakeholders: requirements Stakeholders: requirements sourcessources

‘‘Stakeholders’ are:Stakeholders’ are: Any person, group or thing whichAny person, group or thing which

• Can determine our system’s degree of success or failureCan determine our system’s degree of success or failure• By having an “opinion” aboutBy having an “opinion” about

system performance characteristicssystem performance characteristics system lifecycle constraintssystem lifecycle constraints

Stakeholders determine requirements!Stakeholders determine requirements! Systems engineers determine which requirements the Systems engineers determine which requirements the

stakeholders needstakeholders need• Even if the stakeholders are not currently conscious of those Even if the stakeholders are not currently conscious of those

needs!needs!

Stakeholder: Concept *233 .Stakeholder: Concept *233 .

‘‘Stakeholders’ are: Stakeholders’ are:

Any person, group or thing Any person, group or thing

that can determine our systems degree of success or that can determine our systems degree of success or failure, failure,

by having an opinion aboutby having an opinion about

system performance characteristics and system performance characteristics and

system lifecycle constraints system lifecycle constraints

Functional RequirementsFunctional Requirements



Design

Implementation

Unit Test

System Test

Acceptance Test

What are Actors and Use What are Actors and Use Cases?Cases?

Actors - users of the systemActors - users of the system external entities (people or other systems) external entities (people or other systems)

who interact with the system to achieve a who interact with the system to achieve a desired goal.desired goal.

Use Cases - what happens when Actors Use Cases - what happens when Actors interact with the systeminteract with the system by recording all the ways the system is used by recording all the ways the system is used

(“cases of use”) we accumulate all the goals (“cases of use”) we accumulate all the goals or requirements of the system.or requirements of the system.

Therefore:Therefore:

The Use Case is a collection of sequences of The Use Case is a collection of sequences of actions or events relating to a particular goal.actions or events relating to a particular goal.

The Collection of Use Cases (the Requirements The Collection of Use Cases (the Requirements Specification) should define all system behaviour Specification) should define all system behaviour relevant to the actors to assure them that all relevant to the actors to assure them that all their goals are carried out properly.their goals are carried out properly.

Any system behaviour that is irrelevant to the Any system behaviour that is irrelevant to the actors should not be included in the Use Case.actors should not be included in the Use Case.

Identifying ActorsIdentifying Actors

Who uses the system?Who uses the system? Who installs the system?Who installs the system? Who starts up the system?Who starts up the system? Who maintains the system?Who maintains the system? Who shuts down the system?Who shuts down the system? What other systems use the system?What other systems use the system? Who gets information from this system?Who gets information from this system? Who provides information to the system?Who provides information to the system? Does anything automatically happen at preset times?Does anything automatically happen at preset times?

Examples of ActorsExamples of Actors

Customer

Clerk

ShippingCompany

Supplier

Use Case DiagramUse Case Diagram

Customer

Clerk ShippingCompany

Supplier

PlaceOrder

Get OrderStatus

CalculatePostage

SupplyProduct

DeliverPackage

Use Case: Place OrderUse Case: Place Order

Customer

PlaceOrder

Use Case: Place OrderUse Case: Place Order

Description:Description: This Use Case describes how a customer This Use Case describes how a customer selects an item to purchase and then places an order for selects an item to purchase and then places an order for that item.that item.

Level:Level: Primary task Primary task

Preconditions:Preconditions: The Customer is logged into the system The Customer is logged into the system

Postconditions:Postconditions: A product has been ordered A product has been ordered

Primary Actor:Primary Actor: Customer Customer

Secondary Actors:Secondary Actors: Credit Company Credit Company

Place Order: Flow of EventsPlace Order: Flow of Events

TriggerTrigger: The Customer selects a Product category: The Customer selects a Product category

1.1. The Customer browses the chosen Product category pageThe Customer browses the chosen Product category page

2.2. The Customer selects a specific Product to purchaseThe Customer selects a specific Product to purchase

3.3. The Customer adds the Product to their Shopping CartThe Customer adds the Product to their Shopping Cart

4.4. The Customer may repeat events 1, 2 and 3 to add additional The Customer may repeat events 1, 2 and 3 to add additional items to their Shopping Cartitems to their Shopping Cart

5.5. When ready, the Customer requests that the Order be commited When ready, the Customer requests that the Order be commited toto

6.6. The Credit Company is notified to authorise the Customer’s credit The Credit Company is notified to authorise the Customer’s credit ratingrating

7.7. If the credit rating is positive, the Order will be placedIf the credit rating is positive, the Order will be placed

Nouns as Candidate ClassesNouns as Candidate Classes

TriggerTrigger: The : The CustomerCustomer selects a selects a ProductProduct category category

1.1. The The CustomerCustomer browses the chosen browses the chosen ProductProduct category page category page

2.2. The The CustomerCustomer selects a specific selects a specific ProductProduct to purchase to purchase

3.3. The The CustomerCustomer adds the adds the ProductProduct to their to their Shopping CartShopping Cart

4.4. The The CustomerCustomer may repeat events 1, 2 and 3 to add additional may repeat events 1, 2 and 3 to add additional items to their items to their Shopping CartShopping Cart

5.5. When ready, the When ready, the CustomerCustomer requests that the requests that the OrderOrder be commited be commited toto

6.6. The The Credit CompanyCredit Company is notified to authorise the is notified to authorise the CustomerCustomer’s credit ’s credit ratingrating

7.7. If the credit rating is positive, the If the credit rating is positive, the OrderOrder will be placed will be placed

Place Order: Exceptional EventsPlace Order: Exceptional Events

The Customer may terminate the transaction at The Customer may terminate the transaction at any point before Step 7 and the Order will not be placedany point before Step 7 and the Order will not be placed

2a2a If the Product is out of stock, the customer will be If the Product is out of stock, the customer will be notified and asked to confirm of they wish to continue notified and asked to confirm of they wish to continue with the selectionwith the selection

6a6a If the Customer’s credit rating is not satisfactory, If the Customer’s credit rating is not satisfactory, the transaction will be politely terminated at this pointthe transaction will be politely terminated at this point

DesignDesign



Design

Implementation

Unit Test

System Test

Acceptance Test

Identifying classesIdentifying classes

Think about general properties of the Think about general properties of the domain in which you are workingdomain in which you are working

Identify the nounsIdentify the nouns These form candidate classesThese form candidate classes

A A PublisherPublisher produces and markets a produces and markets a BookBook

A A CustomerCustomer purchases a purchases a BookBook

An An AuthorAuthor writes a writes a BookBook

Publisher Book Customer

Author

Publisher

nameaddresswebSite

Book

bookNumbertitleunitPrice

Customer

nameemailshippingAddress

Author

nameaddresswebSite

AssociationsAssociations

Publisher

nameaddresswebSite

Book


R1

publisher publication

Publisher

nameaddresswebSite

Book


R1

is producedand

marketedby

producesand

markets

Association MeaningsAssociation Meanings

Name the association so that it can be Name the association so that it can be unambiguously identified (e.g. unambiguously identified (e.g. R1R1))

The “association ends” express meaningThe “association ends” express meaning An association end may be a An association end may be a rolerole or a or a

verb phraseverb phrase Each class in an association has a role Each class in an association has a role

(e.g. a (e.g. a BookBook has the role of a has the role of a publicationpublication)) But writing meaning in terms of a verb But writing meaning in terms of a verb

phrase is more descriptivephrase is more descriptive

Publisher

nameaddresswebSite

Book


Customer

nameemailshippingAdd

Author

nameaddresswebSite

R1 R3

R2

is producedand

marketedby

producesand

markets

purchases is sold to

wrote

was written by

MultiplicityMultiplicity

We can also characterise an association We can also characterise an association by the number of instances (objects) that by the number of instances (objects) that participate in each instance of the domain participate in each instance of the domain relationshiprelationship

UML allows specific numbers in a UML allows specific numbers in a multiplicity relationmultiplicity relation

Recommend you only use four kinds:Recommend you only use four kinds: unconditional;unconditional; 1, or 1..*1, or 1..* conditional;conditional; 0..1, or 0..*0..1, or 0..*

Publisher

nameaddresswebSite

Book


Customer


Author

nameaddresswebSite

R1 R3

R2

is producedand

marketedby

producesand

markets

purchases is sold to

wrote

was written by

1 0..* 1..* 0..*

1..*

1..*

There are books not sold to any customer

To be a customer you must have purchased at least one book

But where do I put the number of books a customer purchased?

Publisher

nameaddresswebSite

BookProduct


Customer


Author

nameaddresswebSite

R1 R3

R2

is producedand

marketedby

producesand

markets

is apurchase

of

is sold as

wrote

was written by

1 0..* 1..* 0..*

1..*

1..*

Order

quantitysalePricedate

makes 1..*

is made by 1

DesignDesign



Design

Implementation

Unit Test

System Test

Acceptance Test

Still to DoStill to Do

Formalising Use CasesFormalising Use Cases Strengthening the connection between Strengthening the connection between

requirements and designrequirements and design TestingTesting

internet software development putting it all together paul j krause

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