Noun Phrase Analysis

8/6/2019 Noun Phrase Analysis

http://slidepdf.com/reader/full/noun-phrase-analysis 1/42

October 8, 2004 Software Design 1

Overview of Analysis Analysis is an iterative process« make a µfirstcut¶ conceptual model and then iteratively

refine it as your understanding of the problemincreases.Steps in the analysis process

1. Identifying the classes

2. Identifying the classes attributes andresponsibilities3. Identifying relationships and collaborationsbetween classes




Couple of rulesgood classes provide adequateencapsulationresponsibilities should be well

distributed among all classes (thereshould not be one main class that doesalmost everything)




Case study: a resort reservation

system [1]Design the software to handle reservations at BlueLake Resort. The resort comprises several

cottages and two meeting rooms. Cottages cancomprise from one to three beds. The firstmeeting room has a capacity of 20 persons, thesecond, 40 persons. Cottages can be booked bythe night; meeting rooms can be booked by thehour. Rates for cottages are expressed per person, per night; rates for meeting rooms areexpressed per hour.




Case study: a resort reservation

system [2]Clients can book cottages and meeting rooms inadvance by providing a phone number and a validcredit card information. Customers can expresspreferences for specific cottages. Cancellation of reservations is possible but requires 24 hoursnotice. An administrative charge applies to allcancellations. Every morning, a summary of the

bookings for the previous day is printed out andthe related information is erased from thecomputer; a list of the cottages and meeting roomsthat will require cleaning is printed.






Identification of Classes[2]Using the things to be mode l ed : identifyindividual or group things such as persons,roles, organizations, logs, reports« in theapplication domain that is to be modeled;map to corresponding classesUsing object decomposition (top-downapproach): treat everything as an aggregatethat can be decomposed into parts




Identification of Classes[3]Using gener al iz a tion (bottom-upapproach): look for objects that havecommonalities, and generalize thecorresponding classesUsing previous experience : object-oriented domain analysis, applicationframework, class hierarchies, andpersonal experience




Noun identificationIdentify candidate classes by extractingall nouns out of the requirements/specifications of the system.Don¶t be too selective at first; writedown every class that comes to mind. Aselection process will follow.




Noun identification: Case StudyDesign the software to handle reservations at B l ueLak e Resort . The resort comprises severalcottages and two meeting rooms . Cottages cancomprise from one to three beds . The firstmeeting room has a capacity of 20 persons , thesecond, 40 persons. Cottages can be booked bythe night ; meeting rooms can be booked by thehour . Rates for cottages are expressed per person, per night; rates for meeting rooms areexpressed per hour.




Noun identification: Case StudyClients can book cottages and meeting rooms inadvance by providing a phone number and a valid

credit card information . Customers can expresspreferences for specific cottages. Cancellation of reservations is possible but requires 24 hoursnotice . An administrative charge applies to allcancellations. Every morning , a summary of thebookings for the previous day is printed out andthe related information is erased from thecomputer; a list of the cottages and meeting roomsthat will require cleaning is printed.




Keeping the right candidate

classesHaving made a tentative list of classes, eliminate unnecessary or incorrect classes according to the following criteria:Redundant classes : nouns that express the same informationIrr elevant classes : nouns that have nothing to do with theproblemV ague classes : nouns with ill-defined boundaries or which are toobroadA tt rib utes : nouns referring to something simple with nointeresting behavior, which is simply an attribute of another classE vents o r ope r at ions : nouns referring to something done to thesystem (sometimes events or operations are to be kept: check if they have state, behavior and identity).O uts ide the scope of the system : nouns that do not refer tosomething inside the system




Refined list: Case StudyG ood classes: C ott a ge, Meeting room, Cl ient B ad classes: S oftw a re, B l ue L ak e Resort, B ed,Ca p a city, Night, Hour, R a te, Phone number, C redit c a rd inform a tion, C ustomer, Preference,Ca nce lla tion, Notice, Administr a tive ch a rge, Morning,D a y, Inform a tion, C omputer

D on¶t know: Reserv a tion, Resort, S umm a ry, List




More Class Identification Tips Adjectives can suggest different kinds of objects or different use of the same object. If the adjectives indicate different behavior thenmake a new class.Be wary of sentences in the passive voice, or those whose subjects are not part of thesystem. Recast the sentence in the active

voice and see if it uncovers other classes.e.g.: "a summary of the bookings for theprevious day is printed out". Missing from thissentence is the subject or who is doing theprinting.




More Class Identification TipsKeeping two lists (strong candidatesand weaker ones) is a useful techniqueto avoid losing information while stillsorting between things you are sureabout and things that have yet to besettled. Additional techniques in Step 2(identifying responsibilities andattributes) and Step 3(identifyingrelationships and attributes) will help.




Relationships Association : An Associ a tion is a bi-directional connection between classes

(e.g. the "hires/works for" relationshipbetween an "employee" class and a "boss"class). It is represented by a solid line. Thisline can be qualified with the type of relationship, and can also featuremultiplicity rules (eg. one-to-one, one-to-many, many-to-many) for the relationship.






RelationshipsC ompos it ion: If a class cannot exist byitself, and instead must be a member of

another class, then that class has aComposition relationship with thecontaining class. A Compositionrelationship is indicated by a line with afilled diamond.




RelationshipsD ependency: W hen a class uses another class,perhaps as a member variable or a parameter,and so "depends" on that class, a Dependency

relationship is formed. A D ependency is arelationship where the client does not havesemantic knowledge of the supplier. It can beused, for example to show the relationshipbetween an "encoder" class and a "generic

Algorithm" class that is inserted in runtime to helpit encode a stream. A dependency is shown as adashed line pointing from the client to the supplier.




Relationships




Class notation

A class

ClassName

methods

attributes

A class diagram exhibits classes and their associations used in an application.

Contrast this with a conceptual model which shows domain concepts and their associations.

Note: you can include visibilit y attributes: + for public, ± for private, # for protected






Building a class diagramOnce the interaction diagrams have beencompleted it is possible to identify the specificationfor the software classes and interfaces.The UML has notation to define design details instatic structure, or class diagrams.Conceptual model is also useful in deriving classesby addition of detail.

A class diagram differs from a domain model byshowing software entities rather than real-worldconcepts.




Building a class diagram

(cont.)Typical information in a class diagramincludes:

Classes, associations and attributesInterfaces (with operations and constants)

Attribute type informationMethodsnavigability

dependenciesThe class diagram depends upon the domainmodel and interaction diagrams.




Making class diagrams (1)Identify all classes by examining interactiondiagrams.

Draw them in a class diagram.Duplicate the attributes from the associatedconcepts shown in the conceptual model.

Add method names by examining interactiondiagrams. Add type information to the attributes andmethods.




Making class diagrams (2) Add the associations needed for visibility. Add navigability arrows to indicate thedirection of attribute visibility.

Add dependency relationships to indicatenon-attribute visibility.




ClassesClasses are the building blocks inobject-oriented programming.

Illustrate classes with rectanglesdivided into compartments. Placethe name of the class in the firstpartition (centered, bolded, andcapitalized), list the attributes in

the second partition, and writeoperations into the third.






V is ibi lityU se visibility markers tosignify who can access theinformation contained

within a class. Privatevisibility hides informationfrom anything outside theclass partition. Publicvisibility allows all otherclasses to view the markedinformation. Protectedvisibility allows childclasses to accessinformation they inheritedfrom a parent class.






Mul tip l icity (Cardina l ity)Place multiplicitynotations near the endsof an association. Thesesymbols indicate thenumber of instances of one class linked to one

instance of the otherclass. For example, onecompany will have oneor more employees, buteach employee worksfor one company only.




Place constraints inside curlybraces {}.

Constraint

Simpl e Constra i nt




C ompos it ion and A gg r egat ionC omposition is a special type of aggregation that denotes a strongownership between C lass A, the

whole, andC

lass B, its part. Illustratecomposition with a filled diamond.U se a hollow diamond to represent asimple aggregation relationship, inwhich the "whole" class plays a moreimportant role than the "part" class,but the two classes are notdependent on each other. Thediamond end in both a compositionand aggregation relationship pointstoward the "whole" class or theaggregate.




G ene r al iz at ionG eneralization is anothername for inheritance or an"is a" relationship. It refersto a relationship betweentwo classes where oneclass is a specializedversion of another. Forexample, Honda is a typeof car. So the class Hondawould have ageneralization relationshipwith the class car.






Method names and

multiobjectsThe add() message tothe multiobject should

be interpreted as amessage to thecontainer/ collectionobject.

The add() method isnot part of class Book.

b: Book

2.1: create («)

2.2: add (b):Catalog

:Book




Navigability and dependency

relationshipsNavigability is a property of the role implying visibility of thesource to target class.

Attribute visibility is implied.

Add navigability arrows to the associations to indicate thedirection of attribute visibility where applicable.Common situations suggesting a need to define anassociation with navigability from A to B:

A sends a message to B. A creates an instance of B. A needs to maintain a connection to B

Add dependency relationship lines to indicate non-attributevisibility.




Class diagram

LibraryClerk Accesses Captures

1 1 1 *

1

BookEntrySession

initiateBookEntrySession()makeNewBook()becomeComplete()

isComplete: Boolean;

Book

author titlepublisher

year

Accesses

Contained-in

1

1*

Catalog

makeNewBook()

books: vector;

Terminal

makeNewBookEntry()addBook()

endBookEntry()

Uses

1

1




Conceptual model versus class diagrams

(1)

A S al e in a conceptual model represents asystem concept. A S al e in a class diagram

represents a software entity.






Class diagrams: notables (1)cre a te is a special language independentUML message to indicate instantiation and

initialization. As this is a common operation, itis often omitted from class diagrams.

Access methods for class attributes are alsoomitted from class diagrams to reduce clutter.Messages to a multiobject are not shown asmethods in the class whose objects arecontained in a multiobject.




Class diagrams: notables (2)It is recommended that UML syntax be usedfor method naming. This will keep naming

language independent. UML format:methodN a me(p a r a meterList)

Should all type information be shown in aclass diagram?

If automatic code generation is desired then YES.If the sole purpose is to use the diagram as acommunication aid, then all type information is notof any significant value. ( S ee Fig 21.7 of T1 .)




Class diagrams: navigability (1)

captures1 1

POST

Date

isComplete:booleantime

Sale

DateisComplete:boolean

timemakeLineItem()

POST will likel y have anattribute pointing to Sale.

Navigabilit y arrow: POSTobjects are connected

uni-directionall y to Saleobjects.

No navigabilit y arrow.. Saledoes not have connection

to POST .

Date post:	07-Apr-2018
Category:	Documents
Upload:	kishoreramana
View:	235 times
Download:	0 times

Noun Phrase Analysis

Documents