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Chapter 12Chapter 12Analysis Analysis ModelingModeling

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Analysis Analysis ModelingModeling

A set of models: data, function, and A set of models: data, function, and behavior behavior

Combination of text and diagrammatic Combination of text and diagrammatic formsforms

Different points of view. Different points of view. ReviewedReviewedWork products: data object descriptions, Work products: data object descriptions,

entity relationship diagrams, ….entity relationship diagrams, ….Methods: Structured, Object-oriented, and Methods: Structured, Object-oriented, and

othersothers

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Structure of Analysis Structure of Analysis modelmodel

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Data ModelingData Modeling

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Data Data ModelingModeling

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Why Data Modeling?Why Data Modeling?

examines examines data objectsdata objects independently of processingindependently of processing

focuses attention on the focuses attention on the data data domaindomain

creates a model at the creates a model at the customer’s levelcustomer’s level of abstraction of abstraction

indicates how data objects indicates how data objects relate torelate to one another one another

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What is a Data Object?What is a Data Object?

ObjectObject ——something that is described by a setsomething that is described by a setof attributes (data items) and that will be of attributes (data items) and that will be manipulated within the software (system)manipulated within the software (system)

each each instanceinstance of an object (e.g., a book) of an object (e.g., a book) can be identified uniquely (e.g., ISBN #) can be identified uniquely (e.g., ISBN #)

each plays a necessary role in the systemeach plays a necessary role in the systemi.e., the system could not function without i.e., the system could not function without access to instances of the objectaccess to instances of the object

each is described by attributes that are each is described by attributes that are themselves data itemsthemselves data items

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Typical ObjectsTypical Objects

external entities external entities (printer, user, sensor)(printer, user, sensor)thingsthings (e.g, reports, displays, signals) (e.g, reports, displays, signals) occurrences or events occurrences or events (e.g., interrupt, alarm)(e.g., interrupt, alarm)roles roles (e.g., manager, engineer, salesperson)(e.g., manager, engineer, salesperson)organizational unitsorganizational units (e.g., division, team)(e.g., division, team)placesplaces (e.g., manufacturing floor) (e.g., manufacturing floor)

structures structures (e.g., employee record)(e.g., employee record)

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Identifying ObjectsIdentifying Objectsand Operationsand Operations

define “objects” by define “objects” by underlining all underlining all nouns in the written statement of nouns in the written statement of scopescope

producers/consumers of dataproducers/consumers of data places where data are storedplaces where data are stored ““composite” data itemscomposite” data items

define “operations” by define “operations” by double double underlining all active verbs underlining all active verbs

processes relevant to the applicationprocesses relevant to the application data transformationsdata transformations

consider other “services” that will be consider other “services” that will be required by the objectsrequired by the objects

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Data Objects and Data Objects and AttributesAttributes

A data object contains a set of attributes A data object contains a set of attributes that act as an aspect, quality, character-that act as an aspect, quality, character-istic, or descriptor of the objectistic, or descriptor of the object

object: automobileobject: automobileattributes:attributes: makemake modelmodel body typebody type priceprice options codeoptions code

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What is a Relationship?What is a Relationship?

relationshiprelationship ——indicates “connectedness”; indicates “connectedness”; a "fact" that must be "remembered" a "fact" that must be "remembered" by the system and cannot or is not computed by the system and cannot or is not computed or derived mechanicallyor derived mechanically

several instances of a several instances of a relationship can existrelationship can exist

objects can be related in many objects can be related in many different waysdifferent ways

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Cardinality & Cardinality & ModalityModality

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The ERD: An The ERD: An Example (1)Example (1)

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The ERD: An Example (2)The ERD: An Example (2)

(1,1)(1,1) (1,m)(1,m)placesplacesCustomerCustomer

requestrequestfor servicefor service

generatesgenerates (1,n)(1,n)

(1,1)(1,1)

workworkorderorder

workworktaskstasks

materialsmaterials

consistsconsistsofof

listslists

(1,1)(1,1)(1,w)(1,w)

(1,1)

(1,i)(1,i)

selectedselectedfromfrom

standardstandardtask tabletask table

(1,w)(1,w)

(1,1)(1,1)

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Data Object Type Data Object Type HierarchiesHierarchies

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Associative Data Associative Data ObjectObject

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Function Function ModelingModeling

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Function Function ModelingModeling

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The Flow ModelThe Flow Model

Every computer-based system is an Every computer-based system is an information transform ....information transform ....

computercomputerbasedbased

systemsysteminputinput outputoutput

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Flow Modeling NotationFlow Modeling Notation

external entityexternal entity

processprocess

data flowdata flow

data storedata store

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External EntityExternal Entity

A producer or consumer of dataA producer or consumer of data

Examples: a person, a device, a sensorExamples: a person, a device, a sensor

Another example: computer-basedAnother example: computer-basedsystemsystem

Data must always originate somewhereData must always originate somewhereand must always be sent to somethingand must always be sent to something

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ProcessProcess

A data transformer (changes inputA data transformer (changes inputto output)to output)

Examples: compute taxes, determine area,Examples: compute taxes, determine area,format report, display graph format report, display graph

Data must always be processed in some Data must always be processed in some way to achieve system functionway to achieve system function

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Data FlowData Flow

Data flows through a system, beginningData flows through a system, beginningas input and be transformed into output.as input and be transformed into output.

computecomputetriangle triangle

areaarea

basebase

heightheight

areaarea

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Data StoresData Stores

Data is often stored for later use.Data is often stored for later use.

look-uplook-upsensorsensor

datadata

sensor #sensor #

report requiredreport required

sensor #, type, sensor #, type, location, agelocation, age

sensor datasensor data

sensor numbersensor number

type, type, location, agelocation, age

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ExamplExamplee

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Constructing a DFD—IConstructing a DFD—I

review ERD to isolate data review ERD to isolate data objects and grammatical parse objects and grammatical parse to determine “operations”to determine “operations”

determine external entities determine external entities (producers and consumers of (producers and consumers of datadata

create a level 0 DFDcreate a level 0 DFD

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Level 0 DFD ExampleLevel 0 DFD Example

useruserprocessing processing

requestrequest

videovideosourcesource NTSCNTSC

video signalvideo signal

digitaldigitalvideovideo

processorprocessor

requestedrequestedvideovideosignalsignal

monitormonitor

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Constructing a DFD—IIConstructing a DFD—II

write a narrative describing the write a narrative describing the transformtransform

parse to determine next level parse to determine next level transformstransforms

““balance” the flow to maintain balance” the flow to maintain data flow continuitydata flow continuity

develop a level 1 DFDdevelop a level 1 DFD

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The Data Flow HierarchyThe Data Flow Hierarchy

PPaa bbxx yy

p1p1p2p2

p3p3p4p4 55

aa

bb

cc

ddee

ff

gg

level 0level 0

level 1level 1

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Maps intoMaps into

DFDs: A Look AheadDFDs: A Look Ahead

analysisanalysis modelmodel

design modeldesign model

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Data Flow Diagramming:Data Flow Diagramming:GuidelinesGuidelines

all icons must be all icons must be labeledlabeled with with meaningful namesmeaningful names

the DFD evolves through a the DFD evolves through a numbernumber of levels of detail of levels of detail

always begin with a always begin with a context levelcontext level diagram (also called level 0)diagram (also called level 0)

always show external entities at always show external entities at level 0level 0

always label data flow arrowsalways label data flow arrowsdo notdo not represent procedural logic represent procedural logic

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Behavioral Behavioral ModelingModeling

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Behavior Behavior ModelingModeling

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Behavioral ModelingBehavioral Modeling

Outsideworld

Application

events behavior

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Real-Time Analysis Real-Time Analysis MethodsMethods

each introduces its own notation, each introduces its own notation, but allbut all

• propose an approach for representing propose an approach for representing control and separating it from datacontrol and separating it from data

• provide a mechanism for specifying events, provide a mechanism for specifying events, states, and distributed processingstates, and distributed processing

• begin at the analysis level and work to begin at the analysis level and work to derive processor assignments, tasks and derive processor assignments, tasks and program architectures program architectures

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Control Flow Control Flow DiagramDiagram

(CFD)(CFD)

a vertical bar implies an input to or output from a control a vertical bar implies an input to or output from a control

the control flow diagram is "superimposed" on the DFD the control flow diagram is "superimposed" on the DFD and shows events that control the processes noted in and shows events that control the processes noted in the DFDthe DFD

control flows—events and control items—are noted by control flows—events and control items—are noted by

dashed arrowsdashed arrows

spec (CSPEC) — a separate specification that spec (CSPEC) — a separate specification that describes how control is handleddescribes how control is handled

a dashed arrow entering a vertical bar is an input to the a dashed arrow entering a vertical bar is an input to the CSPECCSPEC

a dashed arrow leaving a process implies a data a dashed arrow leaving a process implies a data conditioncondition

a dashed arrow entering a process implies a control a dashed arrow entering a process implies a control input read directly by the processinput read directly by the process

control flows do not physically activate/deactivate the control flows do not physically activate/deactivate the processes—this is done via the CSPECprocesses—this is done via the CSPEC

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ExamplExamplee

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Extensions for Real-Time Extensions for Real-Time SystemsSystems

Ward & MellorWard & Mellor

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ExamplExamplee

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Extensions for Real-Time Extensions for Real-Time SystemsSystems

Hatley & PirbhaiHatley & Pirbhai

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ExamplExamplee

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The States of a SystemThe States of a Systemstatestate—a set of observable circum-—a set of observable circum-

stances that characterizes the stances that characterizes the behavior of a system at a given behavior of a system at a given timetime

state transitionstate transition—the movement —the movement from one state to anotherfrom one state to another

eventevent—an occurrence that causes —an occurrence that causes the system to exhibit some the system to exhibit some predictable form of behaviorpredictable form of behavior

actionaction—process that occurs as a —process that occurs as a consequence of making a consequence of making a transitiontransition

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State Transition State Transition DiagramDiagram

(STD)(STD)make a list of the different states make a list of the different states

of a system (How does the system of a system (How does the system behave?)behave?)

indicate how the system makes a indicate how the system makes a transition from one state to transition from one state to another (How does the system another (How does the system change state?)change state?)

• indicate eventindicate event• indicate actionindicate action

draw a draw a state transition diagramstate transition diagram

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State Transition State Transition DiagramDiagramNotationNotation

statestate

new statenew state

event causing transitionevent causing transitionaction that occursaction that occurs

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ExampleExample

readingreadingoperatoroperator

commandscommands

making copiesmaking copies reloading paperreloading paper

problem stateproblem state

fullfullinvoke read-op-inputinvoke read-op-input

full and startfull and startinvoke manage-copyinginvoke manage-copying

copies donecopies doneinvoke read-op-inputinvoke read-op-input

emptyemptyinvoke reload paperinvoke reload paper

not jammednot jammedinvoke read-op-inputinvoke read-op-input

jammedjammedinvoke problem-diagnosisinvoke problem-diagnosis

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Data Data DictionaryDictionary

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Data Data DictionaryDictionary

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The Data The Data DictionaryDictionary

a quasi-formal grammar for describing the content of data that the software will process and create a notation for describing control data and the values that control data can take, e.g., "on," or "off" a repository that also contains "where-used" / "how used" information a notation that can be represented manually, but is best developed using CASE tools

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InformatiInformationonName:

Aliases: Where used: How used: Description:

Supplementaryinformation:

the primary name of the composite data item other names for the data item data transforms (processes) that use the composite data item the role of the data item (input, output, temporary storage, etc. a notation for representing content (presented on next slide)

specific information about data types, pre-set values (if known)

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Data Dictionary Data Dictionary NotationNotationNotation

=

+

[ ]

{ }

( ... )

* ... text ...*

n

Meaning

is composed of

and

either-or

n repetitions of

optional data

delimits a comment

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ExamplExamplee

telephone number

Name: Aliases: Where/How used:

Description:

Format:

Telephone number

none

Assess against set-up (output)Dial phone (input)

telephone no. = [ local number | long distance number ] local number = prefix + access numberlong distance number = 1+ area code +local numberarea code = [800 | 888 | 561]prefix = *a three digit number that never starts with 0 or 1*access number = *any four number string*

Build the requirements dictionary:

alphanumeric data

Telephone number tonesDial

phone

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The MechanicsThe Mechanicsof of

Structure AnalysisStructure Analysis

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Data Data ModelingModeling

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ERERDD

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DODODD

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Function Function ModelingModeling

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1. 1. Level 0 Level 0 DFDDFD

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2. 2. Level 1 Level 1 DFDDFD

Underline the first occurrence of all Underline the first occurrence of all nouns and italicize the first occurrence nouns and italicize the first occurrence of all verbs.of all verbs.

Example:Example: … …..SafeHome softwareSafeHome software enablesenables the the

homeownerhomeowner to to configureconfigure the the security systemsecurity system when it is when it is installed,installed, monitorsmonitors all all sensorssensors connectedconnected to to the security system, and the security system, and interacts interacts with the homeowner through a with the homeowner through a key key padpad and and function keysfunction keys containedcontained in in the SafeHome the SafeHome control panelcontrol panel……

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3. 3. Level 2 Level 2 DFDDFD

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Process Specification Process Specification (PSPEC)(PSPEC)

PSPECPSPECnarrativenarrativepseudocode (PDL)pseudocode (PDL)equationsequationstablestablesdiagrams and/or chartsdiagrams and/or charts

bubblebubble

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Creating Mini-SpecsCreating Mini-Specs

SoftwareSoftwareSpecificationSpecification

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5.5. Creating a Process Specification Creating a Process Specification (PSPEC)(PSPEC)

Using PDL

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Behavior Behavior ModelingModeling

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Control Flow Control Flow DiagramDiagram

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Control Specification Control Specification (CSPEC)(CSPEC)

The CSPEC can be:

state transition diagram

state transition table

decision tables

process activation tablescombinatorial spec

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State Transition Diagram State Transition Diagram (STD)(STD)

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Process Activation Table Process Activation Table (PAT)(PAT)

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Data Data DictionaryDictionary

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Data Data DictionaryDictionary

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The Data The Data DictionaryDictionary

a quasi-formal grammar for describing the content of data that the software will process and create a notation for describing control data and the values that control data can take, e.g., "on," or "off" a repository that also contains "where-used" / "how used" information a notation that can be represented manually, but is best developed using CASE tools

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InformatiInformationonName:

Aliases: Where used: How used: Description:

Supplementaryinformation:

the primary name of the composite data item other names for the data item data transforms (processes) that use the composite data item the role of the data item (input, output, temporary storage, etc. a notation for representing content (presented on next slide)

specific information about data types, pre-set values (if known)

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Data Dictionary Data Dictionary NotationNotationNotation

=

+

[ ]

{ }

( ... )

* ... text ...*

n

Meaning

is composed of

and

either-or

n repetitions of

optional data

delimits a comment

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ExamplExamplee

telephone number

Name: Aliases: Where/How used:

Description:

Format:

Telephone number

none

Assess against set-up (output)Dial phone (input)

telephone no. = [ local number | long distance number ] local number = prefix + access numberlong distance number = 1+ area code +local numberarea code = [800 | 888 | 561]prefix = *a three digit number that never starts with 0 or 1*access number = *any four number string*

Build the requirements dictionary:

alphanumeric data

Telephone number tonesDial

phone

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######### The End ######### The End ######################

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Data ModelingData Modeling• Data object description (DOD)Data object description (DOD)

Identify objectsIdentify objects Identify attributesIdentify attributes Build Build data object tabledata object table

• Entity relationship diagram (ERD)Entity relationship diagram (ERD) Identify entity relationshipIdentify entity relationship Identify cardinality & modalityIdentify cardinality & modality Build Build ERDERD

• Data object-type hierarchies, associative data Data object-type hierarchies, associative data objects…objects…

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Function ModelingFunction Modeling• Data Flow Diagram (DFD) Data Flow Diagram (DFD) • Process Specification (PSPEC)Process Specification (PSPEC)

Behavior ModelingBehavior Modeling• Control Flow Diagram (CFD)Control Flow Diagram (CFD)• Control Specification (CSPEC)Control Specification (CSPEC)

State Transition Diagram (STD)State Transition Diagram (STD) Process Activation Table (PAT)Process Activation Table (PAT)

Data DictionaryData Dictionary