CH5.1 CSE230 Chapter 5: Software Specification Chapter 5: Software Specification Prof. Steven A. Demurjian Computer Science & Engineering Department The University of Connecticut 371 Fairfield Road, Box U-2155 Storrs, CT 06269-2155 [email protected]http://www.engr.uconn.edu/~steve (860) 486 – 4818 (860) 486 – 3719 (office) CH5.2 CSE230 Overview Overview of Chapter 5 of Chapter 5 What is a Specification? What is a Specification? Operational and Diagrammatic Specifications Operational and Diagrammatic Specifications Data Flow Diagrams, Finite State Machines, Petri Nets, Entity Relationship Diagrams UML Diagrams (Briefly – Revisit in Total) Mathematical Mathematical- Based Specifications Based Specifications Queueing and Simulation Models Declarative Specifications Logic-Based Notations Algebraic Notations Languages for Modular Specifications Statecharts and Z Specification Notations and Writing Specifications Specification Notations and Writing Specifications
OverviewOverview of Chapter 5of Chapter 5What is a Specification?What is a Specification?Operational and Diagrammatic SpecificationsOperational and Diagrammatic Specifications
Data Flow Diagrams, Finite State Machines, Petri Nets, Entity Relationship DiagramsUML Diagrams (Briefly – Revisit in Total)
MathematicalMathematical--Based SpecificationsBased SpecificationsQueueing and Simulation Models Declarative Specifications
Logic-Based NotationsAlgebraic Notations
Languages for Modular SpecificationsStatecharts and Z
Specification Notations and Writing SpecificationsSpecification Notations and Writing Specifications
2
CH5.3
CSE230
WhatWhat’’s in a Specification?s in a Specification?Specification is Broad Term that Means DefinitionSpecification is Broad Term that Means Definition
Used at Different Stages of Software Development For Different PurposesStatement of Agreement (Contract) Between
Producer and Consumer of A ServiceImplementer and User
All Desirable Qualities Must Be SpecifiedStatement of User RequirementsStatement of User Requirements
Major Failures Occur Due to Misunderstandings Between Producer and User"The Hardest Single Part of Building a SoftwareSystem is Deciding Precisely What To Build" (F. Brooks – Mythical Man Month)
CH5.4
CSE230
WhatWhat’’s in a Specification?s in a Specification?Specification can be Many Different things to Many Specification can be Many Different things to Many Different Stakeholders (User, Designer, Manager, etc.)Different Stakeholders (User, Designer, Manager, etc.)Requirements Specification:Requirements Specification:
Agreement between End User and DesignersDesign Specification:Design Specification:
Agreement between Designers and DevelopersModule Specification:Module Specification:
Agreement between SEs that Use a Module and SEs that Implement a Module re. Interface
ObjectObject--Oriented Specification:Oriented Specification:Assertion of Class’ Capability via Public Interface
External Behavior of SystemFunctional and Non-Function BehaviorDesign Spec Verified Against Requirements Spec
Design SpecificationDescription of Software ArchitectureCode Must be Verified Against Design Spec
Reference Point During Product MaintenanceReference Point During Product MaintenanceVerify that Changes Satisfy RequirementsChange in Specification Requires Adaptive Maintenance
4
CH5.7
CSE230
Classic Information System DesignClassic Information System Design
Inconsistencies May be Impossible to ImplementComplexity May Lead to InconsistencyInconsistencies Lead to Incorrect Implementation
CompletenessCompletenessInternally Complete: Specification Defines any new Concept or Terminology that it UsesW.r.t. Requirements; All Requirements Should be Contained within SpecificationIncrementality Aids Achievement of Completeness
How Does the Achievement of Software Qualities How Does the Achievement of Software Qualities Affect the Attainment of Specification Qualities?Affect the Attainment of Specification Qualities?LetLet’’s See Some Examples of These Qualitiess See Some Examples of These Qualities……
CH5.10
CSE230
Clear, Unambiguous, UnderstandableClear, Unambiguous, UnderstandableSpecification Fragment for a WordSpecification Fragment for a Word--ProcessorProcessorCan an Area be Scattered, or Must it be Contiguous?Can an Area be Scattered, or Must it be Contiguous?
Selecting is the process of designating areas of the document that you want to work on. Most editing and formatting actions require two steps: first you select what you want to work on, such as text or graphics; then you initiate the appropriate action.
6
CH5.11
CSE230
Precise, Unambiguous, ClearPrecise, Unambiguous, ClearConsider a RealConsider a Real--Time SafetyTime Safety--Critical SystemCritical SystemCan a message be accepted as soon as we receive 2 out of 3 identical copies of message or do we need to wait for receipt of the 3rd?
The message must be triplicated. The threecopies must be forwarded through three different physical channels. The receiver accepts the message on the basis of a two-out-of-three voting policy.
CH5.12
CSE230
ConsistentConsistentSpecification Fragment for a WordSpecification Fragment for a Word--ProcessorProcessorWhat if the length of a word exceeds the length of the line?What should the action of the editor be?
The whole text should be kept in lines of equal length. The length is specified by the user. Unless the user gives an explicit hyphenation command, a carriage return should occur only at the end of a word.
7
CH5.13
CSE230
Specification StylesSpecification StylesInformal: Natural Language, Spec by Visio/PPT, Informal: Natural Language, Spec by Visio/PPT, Figures, Tables, etc.Figures, Tables, etc.Formal: Notation with precise Syntax/SemanticsFormal: Notation with precise Syntax/Semantics
Advantages:May Allow Formal VerificationMay Support Automatic Processing (Code Gen)Allows Use of Mathematical ModelsMay be Used to Generate Test Cases (Chapter 6)
Disadvantages:Formal Specifications Not Widely UsedHard to Justify Economic GainTraining Issues for Personnel
SemiSemi--Formal: No Precise Semantics (TDN/GDN)Formal: No Precise Semantics (TDN/GDN)
Describes Desired Behavior of SystemUsually Provides a Model of System BehaviorVerified by Prototyping
DescriptiveDescriptiveDescribes Desired Properties of SystemDeclarative SpecificationUsually Uses Mathematical EquationsMore Abstract than Operation SpecificationNo Focus on Implementation
Actual Specifications Actual Specifications –– Mix of BothMix of Both……
8
CH5.15
CSE230
Operational Specification ExampleOperational Specification ExampleConsider a geometric figure E:Consider a geometric figure E:E can be drawn as follows:1. Select two points P1 and P2 on a plane2. Get a string of a certain length and fix its ends
to P1 and P23. Position a pencil as shown in next figure4. Move the pen clockwise, keeping the string
tightly stretched, until you reach the point whereyou started drawing
P P1 2
CH5.16
CSE230
Verification of SpecificationsVerification of SpecificationsTwo Approaches:Two Approaches:
“Observe” Dynamic Behavior of Specified System (Simulation, Prototyping, “Testing” specs)Analyze Properties of the Specified System
Both Depend on Formality of SpecificationBoth Depend on Formality of SpecificationAnalogy with Traditional EngineeringAnalogy with Traditional Engineering
Physical Model of a BridgeBuild An Actual ModelTest it out in Wind Tunnel
Mathematical Model of a BridgeWhatWhat’’s Reality of Bridge Building?s Reality of Bridge Building?
Guarantee of Success w.r.t. Weight, Weather, etc.Are there Similar Guarantees in Software?Are there Similar Guarantees in Software?What Software Applications Need Such Guarantees?What Software Applications Need Such Guarantees?
9
CH5.17
CSE230
Operational SpecificationsOperational SpecificationsAllow the Behavior of a System to be DefinedAllow the Behavior of a System to be DefinedMany Complementary TechniquesMany Complementary Techniques
Data Flow DiagramsUML Diagrams (Briefly and Separate Lecture)Finite State MachinesPetri Nets
Operational Specifications Provide Means to Model Operational Specifications Provide Means to Model System from Alternative PerspectivesSystem from Alternative Perspectives
Perspectives Must be Consistent with One AnotherSome Techniques Target End-User/CustomerOthers are More Software Engineering IntensiveKey Issue: All Diagrams Must be Consistent in Terminology to Yield Strong Result
CH5.18
CSE230
Data Flow Diagrams (Data Flow Diagrams (DFDsDFDs))A SemiA Semi--Formal Operational SpecificationFormal Operational SpecificationSystem Viewed as Collection of Data Manipulated by System Viewed as Collection of Data Manipulated by ““FunctionsFunctions””Data can be Persistent Data can be Persistent -- Stored in Data RepositoriesStored in Data RepositoriesInput State to Represent Trigger of Data FlowInput State to Represent Trigger of Data FlowOutput Output State(sState(s) to Represent Result of Data Flow) to Represent Result of Data FlowData can Flow from Input to Function to/from Data can Flow from Input to Function to/from Repositories to OutputRepositories to OutputDFDsDFDs have a Graphical Notationhave a Graphical Notation
Tools are Commercially Availablehttp://www.qsee-technologies.com/multi-case.htmhttp://www.aisintl.com/case/products/PowerDesigner/sdesign.html
10
CH5.19
CSE230
DFDsDFDs Employ a Graphical NotationEmploy a Graphical NotationWhat are Main What are Main ModelingModeling Constructs?Constructs?
Note: Note: DFDsDFDs can not Represent Sequential Steps can not Represent Sequential Steps
The function symbol
The data flow symbol
The data store symbol
The input device symbol
The output device symbol
CH5.20
CSE230
Methodology of Information SystemMethodology of Information System
... ...
Input 1
Input2
Inputn
Output1
Output2
Outputm
information
system
1. Start from the “context” diagram
11
CH5.21
CSE230
Methodology of Information SystemMethodology of Information System
A
A1
A3
A2
A4
A5
A6
A7
B1B2
B3B4
Ag
IO
I
O
H
K
J
M
N
P Q
R
S
K
T
K1
K2
K3
K4
M
N
2. Proceed by refinements until you reach “elementary” functions (preserve balancing)
CH5.22
CSE230
A Library Example DFDA Library Example DFD
Shelves
List of Authors
List of titles
List of topics
Title and author of requested book; name of the user
Get a bookBook
List of books borrowed
Book title; user name
Topic request by the user
Search by topics
Book request by the user
Book reception
TopicList of titles referring to the topic
Book
Author
Title
Display of the list of titles
Topic
Title
12
CH5.23
CSE230
Refinement of Refinement of ““Get a bookGet a book””
Shelves
List of Authors
List of titles
Title and author of requested book; name of the user
Book
List of books borrowed
Book title; user name
Book request by the user
Book reception
Book
Author
TitleFind book position
<shelf#, book#>
Get the book
CH5.24
CSE230
Patient Monitoring SystemsPatient Monitoring Systems
The purpose is to monitor the patients’ vital factors--blood,pressure, temperature, …--reading them at specified frequenciesfrom analog devices and storing readings in a DB. If readings fall outside the range specified for patient or device fails an alarmmust be sent to a nurse. The system also provides reports.
Patient
Nurse
PatientMonitoring
Nurse
Persistent data
Report
AlarmDataClinical
ReportRequest
Recent data
Data for report
13
CH5.25
CSE230
A Refinement as Detailed DFDA Refinement as Detailed DFD
Nurse
Nurse
Patient archiveReportRequest
Limits for patient
MonitoringCentral
Limits
Updatearchive
GenerateReport
Data forReport
RecentData
Formatted data
Alarm
PatientClinicalDataMonitoring
Local
Patient data
Report
CH5.26
CSE230
Further RefinementFurther Refinement
Limits
Formatted data alarm
dataPatient
decodeCheck
violations limit
Temperature
Pulse
Pressure
Result
Pressure, pulse…
Formatdata clockDate
Time producemessage
14
CH5.27
CSE230
A HighA High--Level DFD for HTSSLevel DFD for HTSS
CH5.28
CSE230
A HighA High--Level DFD for HTSSLevel DFD for HTSS
15
CH5.29
CSE230
A LowerA Lower--Level DFD for HTSSLevel DFD for HTSS
CH5.30
CSE230
Evaluating Evaluating DFDsDFDsEasy to Read, but Easy to Read, but ……Informal SemanticsInformal Semantics
How Does One Define Leaf Functions?Inherent Ambiguities in Flow
Consider the DFD (Functions) Below:Consider the DFD (Functions) Below:
A
C
E
B
F
D
• Are Outputs from A, B, Call needed Before D isEnabled?
• What if Only A and B Present?• Do A, B, and C have to be
Received in a Particular Order?• Outputs for E and F are
produced at the same time?
16
CH5.31
CSE230
Evaluating Evaluating DFDsDFDsClearly, Control Information is AbsentClearly, Control Information is Absent
DFDsDFDs are a Semiare a Semi--Formal NotationFormal NotationDFDs by Visio and PPTExcellent Vehicle for Presenting to End-UserNot Standalone – Need Complementary Diagram(s) to Fully Specify System Capabilities
BA
Possible interpretations:(a) A produces datum, waits until B consumes it(b) B can read the datum many times without
consuming it(c) a pipe is inserted between A and B
CH5.32
CSE230
Finite state machines (Finite state machines (FSMsFSMs))Utilized to Specify control flow aspectsUtilized to Specify control flow aspectsAn FSM Consists of:
A finite set of states (nodes), Q;A finite set of inputs (labels), I;A transition function d : Q x I Q(d can be a partial function)
FSMs are Well Suited to Represent Systems with
Multiple Known StatesWell-Defined Eventsfor State Changes
a a
b
bc
q
q
q
q
1
20
3
17
CH5.33
CSE230
Classic FSM ExamplesClassic FSM Examples
On Off
Push switch
Push switch
On Off
High-pressure alarm
High-temperature alarm
Restart
CH5.34
CSE230
FSMFSM’’ss Can Model Real WorldCan Model Real WorldConsider a Refinement of High Pressure/High Consider a Refinement of High Pressure/High Temperature FSM on Previous SlideTemperature FSM on Previous Slide
Pressure signal Temperature signal
Successful recovery
Unsuccessful recovery
OffNormal
Pressure action
OffNormal
Pressure action
Temperature signal Temperature action
Successful recovery
Unsuccessful recovery
Pressure signal
18
CH5.35
CSE230
FSM for HTSSFSM for HTSSTotals a CustomerTotals a Customer’’s Orders Order
ProcessPayment
No More Coupons
Next Coupon
CH5.36
CSE230
Classes of Classes of FSMsFSMsDeterministic/NondeterministicDeterministic/NondeterministicFSMsFSMs as Recognizers as Recognizers -- Introduce Final StatesIntroduce Final StatesFSMsFSMs
Used for Lexical Analysis in CompilersRealize Regular Expressions in Automata
q
q q q q
q q
q
b
e g i
n
e
n
d
0
1 2 3 4
5 6
fq0 is an initial stateqf is a final state
19
CH5.37
CSE230
FSMsFSMs as Recognizersas RecognizersFSMsFSMs as transducers as transducers -- introduce set of outputsintroduce set of outputs
q<letter>
<letter>
_
<digit>
q q
<letter>Legend: is an abbreviation for a set of arrows
labeled a, b,..., z, A,..., Z, ti l
is an abbreviation for a set of arrows labeled 0, 1,..., 9, respectively<digit>
0 1 2
<letter>
<digit>
CH5.38
CSE230
FSM Usage and LimitationFSM Usage and LimitationFSMsFSMs are Simple and Widely Usedare Simple and Widely Used
Control Systems, CompilationPattern Matching, Hardware Design
Most Software Applications can be Modeled via Most Software Applications can be Modeled via FSMsFSMsIn Practice, In Practice, FSMsFSMs are Good for Sample or Portions of are Good for Sample or Portions of System System –– Problems Can Arise:Problems Can Arise:
Model Different Portions of ApplicationCompose FSMs for Entire System View Finite Memory Yields State Explosion
Suppose n FSMs with k1, k2, … kn statesComposition is a FSM with k1 * k2 *… * kn.
This growth is exponential with the number of FSMs, not linear (we would like it to be k1 + k2 +… + kn )
20
CH5.39
CSE230
Example of State Explosion:Example of State Explosion:Consider Three Individual Consider Three Individual FSMsFSMs::
Producer
p1
c 2
Storage
1
produce
deposit
get
consume
deposit
get get
deposit
p2
Consumer
c 1
20
CH5.40
CSE230
Composition: The Resulting FSMComposition: The Resulting FSMClearly, Complexity Has IncreasedClearly, Complexity Has Increased
<0, p ,c >
<0, p ,c >
consume
produce
consume
produce
consume
produce
consume
produce
produce produce
consume consume
write
read
write
read
read
write
read
write
1
12
<0, p , c >
1
2 2
<1, p ,c >
<0, p ,c >
1 1
<1, p ,c>
<1, p ,c >
<1, p ,c >
2 1
1 2
1
2
2 2 <2, p ,c > 2 2
<2, p ,c > 1 2
<2, p ,c >2 1
<2, p ,c > 1 1
21
CH5.41
CSE230
Petri NetsPetri NetsPetri Nets are Another Graphical Formalism for Petri Nets are Another Graphical Formalism for SystemSystem’’s Specification Consisting of:s Specification Consisting of:
Finite Set of Places (Circles – Pi’s)Finite set of Transitions (Horizontal Lines – tj’s)Finite Set of Arrows Connecting Places to Transitions and Transitions to PlacesTokens (Dots) P
P
P
t
tP
t
1
3
1
3
4
65
P
P
P
2
5
7
t
t
t
2
4
6
CH5.42
CSE230
Petri Nets Petri Nets –– Other ConceptsOther ConceptsMarking: Assigning NonMarking: Assigning Non--Negative Integers to Places Negative Integers to Places Which Represent Tokens in the NetworkWhich Represent Tokens in the NetworkState: Petri Net with MarkingState: Petri Net with MarkingEnabled: Transition if all of its Incoming Places have Enabled: Transition if all of its Incoming Places have at Least One Tokenat Least One TokenFire: Transition Consumes Token from Incoming Fire: Transition Consumes Token from Incoming Places and Produces Token for Outgoing PlacesPlaces and Produces Token for Outgoing PlacesFiring Sequence: Sequence of Transition Firings for Firing Sequence: Sequence of Transition Firings for Execution of PN (tExecution of PN (t11, t, t33, t, t22, t, t55, , ……))PNsPNs are Nonare Non--DeterministicDeterministic
Any Enabled TransitionMay FireNeither When Nor Which Fires is Specified by Model
P
P
P
t
tP
t
1
3
1
3
4
65
P
P
P
2
5
7
t
t
t
2
4
6
22
CH5.43
CSE230
Modeling with Petri netsModeling with Petri netsPlaces Represent Distributed StatesPlaces Represent Distributed StatesTransitions Represent Actions Or Events That May Transitions Represent Actions Or Events That May Occur When System is in a Certain StateOccur When System is in a Certain StateThey Can Occur as Certain Conditions Hold on the They Can Occur as Certain Conditions Hold on the StatesStatesForks and Joins ModeledForks and Joins Modeled
Fork: Transition from 1 Input to N OutputsJoin: Transition fron N Inputs to 1 Output
P
P
P
t
tP
t
1
3
1
3
4
65
P
P
P
2
5
7
t
t
t
2
4
6
CH5.44
CSE230
Petri NetsPetri NetsA Petri Net is Defined as a Quadruple (P,T,F,W) with:A Petri Net is Defined as a Quadruple (P,T,F,W) with:P: places T: transitions (P, T are finite) F: flow relation (F ⊆ {P×T} ∪ {T×P} )W: weight function (W: F N – {0} )Properties:(1)P ∩ T = Ø(2) P ∪ T ≠ Ø(3)F ⊆ (P × T) ∪ (T × P)(4)W: F → N-{0}Default Value of Weight Function W is 1Default Value of Weight Function W is 1State Defined by Marking: State Defined by Marking: M: P M: P NN
23
CH5.45
CSE230places
transitions flows
marking
3 weightP
P
P
t
tP
t
1
3
1
3
4
6
5
P
P
P
2
5
7
t
t
t
2
4
6
Graphical Representation of PNGraphical Representation of PN
CH5.46
CSE230
PN Semantics: Dynamic EvolutionPN Semantics: Dynamic EvolutionTransition t is Enabled Transition t is Enabled iffiff
∀p ∈ t's Input Places, M(p) ≥ W(<p,t>)Transition t Fires: Produces a New Marking MTransition t Fires: Produces a New Marking M’’ in in Places that are Either Places that are Either t'st's Input or Output or BothInput or Output or Both
If p is an Input Place: M'(p) = M(p) - W(<p,t>)Consume a TokenIf p is an Output Place: M'(p) = M(p) + W(<t,p>)Produce a TokenIf p is both an Input and an Output Place: M'(p) = M(p) - W(<p,t>) + W(<t,p>)Consume and Produce a Token
24
CH5.47
CSE230
After (a) either (b) or (c) may occur, then (d)P
P
P
t
tP
t
1
3
1
3
4
65
P
P
P
2
5
7
t
t
t
2
4
6
P
P
P
t
tP
t
1
3
1
3
4
65
P
P
P
2
5
7
t
t
t
2
4
6
P
P
P
t
tP
t
1
3
1
3
4
65
P
P
P
2
5
7
t
t
t
2
4
6
P
P
P
t
tP
t
1
3
1
3
4
65
P
P
2
5
7
t
t
t
2
4
6
P
(a) (b)
(c) (d)
CH5.48
CSE230
Modeling Concurrent SystemsModeling Concurrent SystemsConcurrency: Concurrency: Two Transitions are Enabled to Fire in Two Transitions are Enabled to Fire in Given State, and the Firing of One Does Nor Prevent Given State, and the Firing of One Does Nor Prevent the Other From Firing the Other From Firing
See t1 and t2 in Case (a)Conflict: Conflict: Two Transitions are Enabled to Fire in Given Two Transitions are Enabled to Fire in Given State, But the Firing of One Prevents the Other From State, But the Firing of One Prevents the Other From FiringFiring
See T3 and T4 in Case (d)Place P3 Models Shared Resource Between Two Processes
No Policy Exists to Resolve Conflicts (Known as No Policy Exists to Resolve Conflicts (Known as Unfair Scheduling)Unfair Scheduling)A Process May Never Get a Resource (Starvation)A Process May Never Get a Resource (Starvation)Deadlock: A Marking Where no Transition May be Deadlock: A Marking Where no Transition May be EnabledEnabled
25
CH5.49
CSE230
Avoiding StarvationAvoiding StarvationFocus on Cycle in Middle of PNFocus on Cycle in Middle of PN
P P
P
P P
t t
t t
P P
t t
1
1 2
3
4
5
6
7
4
2
3
6
5
imposes alternation
CH5.50
CSE230
A ConflictA Conflict--Free PNFree PNAlways a Token Available in Place R for Both Sides Always a Token Available in Place R for Both Sides to Utilize to Utilize -- R Reloaded with 2 Tokens at Each StepR Reloaded with 2 Tokens at Each Step
R
P P
t t
t'
t"
t
t'
t"
t
1
1
3
3
2
2
4
4
56
2 2
this net candeadlock!consider
>< '42
'31 t,t , t,t
26
CH5.51
CSE230
A DeadlockA Deadlock--Free PNFree PNIf One Side Uses 2, it Proceeds, Else Other SideIf One Side Uses 2, it Proceeds, Else Other SideStarvation is Still PossibleStarvation is Still Possible
R
P P
t t
t'
t"
t
t'
t"
t
1
1
3
3
2
2
4
4
56
2 2
2 2
CH5.52
CSE230
A Partial StarvationA Partial StarvationPlace Supplying t4 is Not Refilled with TokenPlace Supplying t4 is Not Refilled with Token
t
t
1
3
t
t
2
4
27
CH5.53
CSE230
ProducerProducer--Consumer Example Consumer Example Individual Individual PNsPNs for Produce and Consumefor Produce and Consume
Petri Net LimitationsPetri Net LimitationsPetri Nets are Limited in Their Modeling CapabilityPetri Nets are Limited in Their Modeling Capability
As Presented, Non-DeterministicNo Way to Prioritorize Among All Eligible Active Transitions that Can Fire
There are a Number of Capabilities that Would be There are a Number of Capabilities that Would be Very Useful in Modeling System BehaviorVery Useful in Modeling System Behavior
Adding Predicates and Functions that are Used to Evaluate Conditions Under Which a Transition Fire and its ResultsInstituting Priority to Decide When to Fire Among Multiple Transitions that are EligibleIncorporating Timing to Constrain When a Transition can Fire
CH5.56
CSE230
Assigning Values to TokensAssigning Values to TokensTransitions have Predicates and FunctionsTransitions have Predicates and FunctionsPredicate Refers to Values of Tokens in Inputs Predicate Refers to Values of Tokens in Inputs Functions Define Values of Tokens for OutputsFunctions Define Values of Tokens for Outputs
PP
P
PP
34
71 4
t t1 2
45
12
3Predicate P2 > P1 and function P4 := P2 + P1 associated with t1
Predicate P3 = P2 and functions P4 := P3 − P2 and P5 := P2 + P3 are associated with t2
The firing of t1 by using <3,7> would produce the value 10 in P4. t2 can then fire using <4, 4>
29
CH5.57
CSE230
Other PN ExtensionsOther PN ExtensionsSpecifying PrioritiesSpecifying Priorities
Function Pri from Transitions to Natural Numbers:pri: T N
When Several Transitions are Enabled, Only Ones with Maximum Priority are Allowed to FireIf Multiple Active, choose Non-deterministically
TimingTimingPair of Constants <tmin, tmax> associated with each Transition – If Transition Enabled
Must wait for at least tmin to elapse before it can FireMust Fire before tmax has elapsed, unless it is Disabled by the Firing of another Transition before tmax
CH5.58
CSE230
Combining Timing and PrioritiesCombining Timing and Priorities
P P
P
t t t
tm in = 1 tm a x = 4
tm in = 2 tm a x = 3
tm in = 0 tm a x = 5
pr ior ity = p r ior ity = p r ior ity = 1 3 2
P
1
1 2
2
3
3
4
30
CH5.59
CSE230
Overview of a PN ExampleOverview of a PN ExamplePNsPNs can be Used for Very Complex Applications can be Used for Very Complex Applications ConsiderConsider
An N Elevator System to be Installed in a Building with M FloorsNatural Language Specifications Contain Several AmbiguitiesFormal Specification Using PNs Removes Ambiguities
How is a Solution Constructed?How is a Solution Constructed?Employ ModulesEach Encapsulating Fragments of PNsEach Captures Certain System Components
CH5.60
CSE230
Initial Sketch of MovementInitial Sketch of Movement
Elevator at floor j
Elevator at floor j + 1
Pushing internal button for floor j + 1
Button illuminationTransfer
from floor j to j+1
31
CH5.61
CSE230
Dealing with ButtonsDealing with Buttons
ILBj
Fj
Set
Reset
OffOn0..0
InternalInternal
ExternalExternalSet
x..x Reset
ti'
Fj
Fj'
On Off
UPj
CH5.62
CSE230
Fj+1 UFj+1
Fj"
tFj'
UPh On
On DOWNh
ILBh
DOWNj+1
On
On
On
On
ILBj+1
Fj
t1 t2 t3 t4 t5 t6
t7 t8
t9
t10
t11 t12
UPj+1
Modeling the Entire PNModeling the Entire PN
32
CH5.63
CSE230
Entity Relationship DiagramsEntity Relationship DiagramsER Model ConceptsER Model Concepts
Entities and AttributesEntity Types, Value Sets, and Key AttributesRelationships and Relationship TypesWeak Entity TypesRoles and Attributes in Relationship Types
Relationships of Higher DegreeRelationships of Higher DegreeSkip Extended EntitySkip Extended Entity--Relationship (EER) ModelRelationship (EER) ModelNotation is based on :Notation is based on :
R. Elmasri and S.B. Navathe, “ Fundamentals of Database Systems,” Ed. 3., Addison Wesley, 2000, Chapters 3 and 4.
CH5.64
CSE230
Summary of ERSummary of ER--Diagram NotationDiagram NotationMeaningMeaning
ENTITY TYPEENTITY TYPE
WEAK ENTITY TYPEWEAK ENTITY TYPE
RELATIONSHIP TYPERELATIONSHIP TYPE
IDENTIFYING RELATIONSHIP TYPEIDENTIFYING RELATIONSHIP TYPE
ATTRIBUTEATTRIBUTE
KEY ATTRIBUTEKEY ATTRIBUTE
MULTIVALUED ATTRIBUTEMULTIVALUED ATTRIBUTE
COMPOSITE ATTRIBUTECOMPOSITE ATTRIBUTE
DERIVED ATTRIBUTEDERIVED ATTRIBUTE
TOTAL PARTICIPATION OF ETOTAL PARTICIPATION OF E22 IN RIN R
CARDINALITY RATIO 1:N FOR ECARDINALITY RATIO 1:N FOR E11:E:E2 2 IN RIN R
STRUCTURAL CONSTRAINT (min, max) ON STRUCTURAL CONSTRAINT (min, max) ON PARTICIPATION OF E IN RPARTICIPATION OF E IN R
Symbol
E1 R E2
E1 R N E2
R(min,max)
E
N
33
CH5.65
CSE230
Example COMPANY DatabaseExample COMPANY DatabaseRequirements of the Company (Oversimplified for Requirements of the Company (Oversimplified for Illustrative Purposes)Illustrative Purposes)
Company is Organized into DepartmentsEach Department has a Name, Number and an Employee Who Manages the DepartmentWe Track of the Start Date of the Department Manager
Each Department Controls a Number of Projects Each Project has a Name, Number and is Located at a Single Location
CH5.66
CSE230
Example COMPANY Database (Cont.)Example COMPANY Database (Cont.)Store Each Employee’s Social Security Number, Address, Salary, Sex, and Birthdate
Each Employee Works for One Department but May Work on Several Projects We Track of the Number of Hours Per Week that an Employee Currently Works on Each ProjectWe Track of the Direct Supervisor of Each Employee
Each Employee May have a Number of Dependents
For Each Dependent, We Track of their Name, Sex, Birthdate, and Relationship to Employee
34
CH5.67
CSE230
ER Diagram for the Company DatabaseER Diagram for the Company Database
CH5.68
CSE230
ER Model Concepts: Entities and AttributesER Model Concepts: Entities and AttributesEntities Entities -- Specific Objects or Things in the MiniSpecific Objects or Things in the Mini--world world that are Represented in the Databasethat are Represented in the Database
EMPLOYEE John SmithResearch DEPARTMENTProductx PROJECT
Attributes are Properties Used to Describe an EntityAttributes are Properties Used to Describe an Entitye.g., an EMPLOYEE Entity may have a Name, SSN, e.g., an EMPLOYEE Entity may have a Name, SSN, Address, Sex, Address, Sex, BirthdateBirthdateA Specific Entity (Instance) has a Value for Each of A Specific Entity (Instance) has a Value for Each of its Attributesits Attributes
Specific Employee Entity May Have Name=‘John Smith’, SSN=‘123456789’, Address=‘731 Fondren, Houston, TX’, Sex=‘m’, Birthdate=‘09-jan-55’
35
CH5.69
CSE230
Three Types of AttributesThree Types of AttributesSimple: Single Atomic Value for the AttributeSimple: Single Atomic Value for the Attribute
SSN or Sex or State or Salary or ...Composite: Attribute Composed of Many ComponentsComposite: Attribute Composed of Many Components
Address (Apt#, House#, Street, City, State, Zipcode, Country) or Name(Fname, MI, Lname)Composition May form a Hierarchy where Some Components are Themselves Composite
MultiMulti--Valued: Entity may have Multiple Values for Valued: Entity may have Multiple Values for That Attribute That Attribute -- Like an Set TypeLike an Set Type
CAR {Color} or STUDENT {Previousdegrees}Composite and MultiComposite and Multi--valued Attributes may be Nested valued Attributes may be Nested Arbitrarily to any Number of Levels (Rare) Arbitrarily to any Number of Levels (Rare)
Previousdegrees of a STUDENT is a Composite Multi-valued Attribute Denoted by {Previousdegrees(college, Year, Degree, Field)}
CH5.70
CSE230
Entities with Attribute ValuesEntities with Attribute Values
36
CH5.71
CSE230
Entity Types and Key AttributesEntity Types and Key AttributesEntities with the Same Basic Attributes Are Grouped Entities with the Same Basic Attributes Are Grouped or Typed into an or Typed into an Entity TypeEntity Type
EMPLOYEE Entity Type or PROJECT TypeAttribute of Entity Type for which Each Entity Must Attribute of Entity Type for which Each Entity Must Have a Unique Value is Called a Have a Unique Value is Called a Key AttributeKey Attribute
SSN of EMPLOYEE, ISBN of BOOKA Key Attribute may be CompositeA Key Attribute may be Composite
VIN is a Key of the CAR Entity TypeAn Entity Type may have More than One KeyAn Entity Type may have More than One Key
CAR Entity Type May Have Two Keys:VINVehicletagnumber (Number, State) aka License Plate
CH5.72
CSE230
car1((ABC 123, TEXAS), TK629, Ford Mustang, convertible, 1989, (red, black))
car2((ABC 123, NEW YORK), WP9872, Nissan Sentra, 2-door, 1992, (blue))
car3((VSY 720, TEXAS), TD729, Chrysler LeBaron, 4-door, 1993, (white, blue))
Entity Type CAR with AttributesEntity Type CAR with Attributes
37
CH5.73
CSE230
Two Other Entity TypesTwo Other Entity Types
CH5.74
CSE230
Relationships and Relationship TypesRelationships and Relationship TypesA Relationship Relates Two or More Distinct Entities A Relationship Relates Two or More Distinct Entities With a Specific MeaningWith a Specific Meaning
EMPLOYEE John Smith Works on the ProductxPROJECT EMPLOYEE Franklin Wong Manages the Research DEPARTMENTRelationship - Instance Level
Relationships of the Same Type are Grouped or Typed Relationships of the Same Type are Grouped or Typed Into a Relationship TypeInto a Relationship Type
WORKS_ON Relationship Type in Which Employees and Projects ParticipateMANAGES Relationship Type in Which Employees and Departments ParticipateAnalogous to Reference or List in Programming
38
CH5.75
CSE230
The WORKS_ON RelationshipThe WORKS_ON Relationship
CH5.76
CSE230
Relationships and Relationship TypesRelationships and Relationship TypesDegree of a Relationship Type is the Number of Degree of a Relationship Type is the Number of Participating Entity TypesParticipating Entity Types
Both MANAGES and WORKS_ON are Binary RelationshipsWhat is a possible Ternary Relationship?
More Than One Relationship Type Can Exist With the More Than One Relationship Type Can Exist With the Same Participating Entity TypesSame Participating Entity Types
MANAGES and WORKS_FOR are Distinct Relationships Between EMPLOYEE and DEPARTMENT Entity Types
Relationships are DirectionalRelationships are DirectionalSUPPLIES: SUPPLIER to PARTSSUPPLIERS: PARTS to SUPPLIER
39
CH5.77
CSE230
EE--R DiagramsR Diagrams
EMPLOYEE PROJECT
Responsibility
Duration
Budget
ProjectNameProject NoEmployee No Employee
Name
SalaryTitle
WORKS ON
Address
CityApt. #
Street #
NoEmp
Location
CH5.78
CSE230
Weak Entity TypesWeak Entity TypesEntity that Does Not have a Key AttributeEntity that Does Not have a Key AttributeWeak Entity Must Participate in an Identifying Weak Entity Must Participate in an Identifying Relationship Type with an Owner or Identifying Entity Relationship Type with an Owner or Identifying Entity TypeTypeEntities are Identified by the Combination of:Entities are Identified by the Combination of:
A Partial Key of the Weak Entity TypeParticular Entity they Are Related to in the Identifying Entity Type
Example: Example: A DEPENDENT Entity is Identified by Dependent’s First Name and Birthdate, and the EMPLOYEE That the Dependent is Related to DEPENDENT is a Weak Entity Type With EMPLOYEE as its Identifying Entity Type Via the Identifying Relationship Type DEPENDENT_OF
40
CH5.79
CSE230
ER Model and Data AbstractionER Model and Data AbstractionAbstractionAbstractionClassificationClassification
ER Model ConceptER Model ConceptEntity Type Entity Type -- a a Grouping of Member Grouping of Member EntitiesEntitiesRelationship Type Relationship Type -- a a Grouping of Member Grouping of Member RelationshipsRelationshipsRelationship Type is an Relationship Type is an Aggregation of (Over) Aggregation of (Over) Its Participating Entity Its Participating Entity TypesTypesWeak Entity Type and Weak Entity Type and Attribute KeyAttribute Key????????????????
CH5.80
CSE230
Constraints on AggregationConstraints on AggregationCardinality Constraints on Relationship TypesCardinality Constraints on Relationship Types
AKA Ratio ConstraintsMaximum Cardinality
One-to-OneOne-to-ManyMany-to-Many
Minimum Cardinality (AKA Participation or Existence Dependency Constraints)
Zero (Optional Participation, Not Existence-Dependent)One or More (Mandatory, Existence-Dependent)
41
CH5.81
CSE230
e1
e2
e3
e4
e5
e6
e7
EMPLOYEE
r1
r2
r3
r4
r5
r6
r7
WORKS_FOR
d1
d2
d3
DEPARTMENT
OneOne--toto--many(1:N) or Manymany(1:N) or Many--toto--one (N:1)one (N:1)
CH5.82
CSE230
e1
e2
e3
e4
e5
e6
e7
r1
r2
r3
r4
r5
r6
r7
d1
d2
d3
r8
r9
MANYMANY--TOTO--MANY(M:N)MANY(M:N)
42
CH5.83
CSE230
EMPLOYEE PROJECT
Responsibility
Duration
Budget
ProjectNameProject NoEmployee No Employee
Name
SalaryTitle
WORKS ON1 1
OneOne--toto--One RelationshipOne RelationshipEach Instance of One Entity Class E1 Can Be Each Instance of One Entity Class E1 Can Be Associated with Exactly One Instance of Another Associated with Exactly One Instance of Another Entity Class E2 and Vice Versa.Entity Class E2 and Vice Versa.Example:Example:
Each Employee Can Work in Exactly One Project and Each Project Employs Exactly One Employee
ManyMany--toto--One RelationshipOne RelationshipEach Instance of One Entity Class E1 can be Each Instance of One Entity Class E1 can be Associated with Zero or More Instances of Another Associated with Zero or More Instances of Another Entity Class E2, but Each Instance of E2 can be Entity Class E2, but Each Instance of E2 can be Associated With at Most 1 Instance of E1Associated With at Most 1 Instance of E1Example :Example :
Each Employee Can Work in Exactly One Project Each Project Can Employ Many Engineers
ManyMany--toto--Many RelationshipMany RelationshipEach Instance of One Entity Class Can Be Associated Each Instance of One Entity Class Can Be Associated with Many Instances of Another Entity Class, and vice with Many Instances of Another Entity Class, and vice versaversaExample:Example:
Each Employee Can Work in Many ProjectsEach Project Can Employ Many Employees
Structural Constraints Structural Constraints Structural Constraints on a Relationship are One Way Structural Constraints on a Relationship are One Way to Express the Semantics of a Relationship to Express the Semantics of a Relationship Cardinality Ratio (of a Binary Relationship): 1:1, 1:N, Cardinality Ratio (of a Binary Relationship): 1:1, 1:N, N:1, or M:N N:1, or M:N
Shown by Placing Apropos Number on the LinkParticipation Constraint (on Each Entity Type): Participation Constraint (on Each Entity Type):
Total (Called Existence Dependency) or PartialShown By Double Lining The Link
NOTE: NOTE: Easy to Specify for Binary Relationship TypesDo Not Be Misled by Obscure Notations to Specify Above Constraints for Higher Order Relationships
CH5.90
CSE230
Relationships of Higher DegreeRelationships of Higher DegreeRelationship Types of Degree 2 Are Called BinaryRelationship Types of Degree 2 Are Called BinaryRelationship Types of Degree 3 Are Called Ternary Relationship Types of Degree 3 Are Called Ternary
There is a Concrete Relationship Instance that Involves all Three Entity TypesThese are Not Separate Relationships!
Relationship Types of Degree N Are Called NRelationship Types of Degree N Are Called N--aryaryAgain - Concrete n-Participation Relationship
In General, an NIn General, an N--aryary Relationship is Not Equivalent to Relationship is Not Equivalent to N Binary RelationshipsN Binary Relationships
Rather - it is more Analogous to the Grouping of N-Binary Relationships into a N-ary Relationship
46
CH5.91
CSE230
Ternary RelationshipsTernary Relationships
CH5.92
CSE230
Ternary RelationshipsTernary Relationships
47
CH5.93
CSE230
Ternary vs. Binary RelationshipsTernary vs. Binary Relationships
Another ER Diagram Another ER Diagram -- Bank ExampleBank Example
49
CH5.97
CSE230
What are Problems with ER Notation?What are Problems with ER Notation?Historically, ER Model 1st Proposed in 1976Historically, ER Model 1st Proposed in 1976
P. Chen, ''The Entity-Relationship Model - Toward a Unified View of Data,'' ACM Trans. on Database Systems, Vol. 1, No. 1, March 1976.
However, ER Model in this Original Form Did Not However, ER Model in this Original Form Did Not Support the Generalization Abstraction (Inheritance)Support the Generalization Abstraction (Inheritance)In Databases, Inheritance 1st Proposed in 1977In Databases, Inheritance 1st Proposed in 1977
J. Smith and D. Smith, ''Database Abstractions: Aggregation and Generalization,'' ACM Trans. on Database Systems, Vol. 2, No. 2, June 1977.
Thus, Extended ER Evolved through 1980s with the Thus, Extended ER Evolved through 1980s with the Focus on Focus on ““Semantic Data ModelsSemantic Data Models””
M. Hammer and D. McLeod, ''Database Descriptions with SDM: A Semantic Data Model,'' ACM Trans. on Database Systems, Vol. 6, No. 3, Sept. 1981.
CH5.98
CSE230
Specialization/Attribute InheritanceSpecialization/Attribute InheritanceAn Entity Type E1 is a Specialization of another Entity Type E2 if E1 has the Same Properties of E2 and Perhaps Even More.E1 IS-A E2
MANAGER
EMPLOYEE
∪
EMPLOYEE
Employee No EmployeeName
Salary
Title Address
MANAGER
Employee No EmployeeName
Salary
Title Address
Expense Act. Condo∪
50
CH5.99
CSE230
GeneralizationGeneralizationAbstracting the Common Properties of Two or More Entities to Produce a “Higher-level” Entity
ENGINEER SECRETARY SALESPERSON
Employee NoEmployee Name
SalaryTitle
Address
Employee NoEmployee Name
SalaryTitle
Address
Employee NoEmployee Name
SalaryTitle
Address
ProjectOffice Office
SpecialtyCarRegion
EMPLOYEE Employee NoEmployee Name
SalaryTitle
Address
CH5.100
CSE230
GeneralizationGeneralization
ENGINEER SECRETARY SALESPERSON
EMPLOYEE
Employee No EmployeeName
Salary
Title Address
Project Office Specialty Office CarRegion
∪d
51
CH5.101
CSE230
ConstraintsConstraints
disjoint, totaldisjoint, total
disjoint, partialdisjoint, partiald
d
o
o
overlapping, total
overlapping, partial
∪∪
Part
Manufactured_Part
Purchased_Part
o
PartNo Description
SupplierName ListPrice
BatchNo
M_date
DrawingNo
CH5.102
CSE230
Total and Partial DisjointTotal and Partial Disjoint
EMPLOYEE
Employee No EmployeeName
Salary
Title Address
SECRETARYENGINEER
Project Office Specialty Office
SALESPERSON
CarRegion
∪ ∪∪
dd
HOURLY_EMP
SALARIED_EMP
Hourly Rate
Salary
∪∪
52
CH5.103
CSE230
Total OverlappingTotal Overlapping
PART
Part No PartName
QTY
WGT
o
MANUFACTURED_PART PURCHASED_PART
Batch No Drawing No Price
∪ ∪
CH5.104
CSE230
HTSS ER Diagram ExampleHTSS ER Diagram Example
53
CH5.105
CSE230
HTSS ER Diagram ExampleHTSS ER Diagram Example
CH5.106
CSE230
Interplay of Specification TechniquesInterplay of Specification TechniquesWhat do What do DFDsDFDs have to Offer re. OO Design?have to Offer re. OO Design?
Data Stores (Classes)Arrow Labels (Parameters)Input (Method of Class)Functions (Implementation of Method of Class)Output (Return of Method of Class)
What do What do DFDsDFDs have to Offer re. ER Design?have to Offer re. ER Design?Data Stores (Entities)Arrow Labels (Relationships and Keys)
What about What about FSMsFSMs? ? What is Impact What is Impact w.r.tw.r.t. Modular or ADT/Class Design?. Modular or ADT/Class Design?
54
CH5.107
CSE230
Interplay of Specification TechniquesInterplay of Specification Techniques
CH5.108
CSE230
Interplay of Specification TechniquesInterplay of Specification Techniques
55
CH5.109
CSE230
UML DiagramsUML DiagramsUML is a Language for UML is a Language for Specifying, Visualizing, Specifying, Visualizing, Constructing, and Documenting Software ArtifactsConstructing, and Documenting Software ArtifactsUML Formalizes the Previous Techniques (DFD, ER, UML Formalizes the Previous Techniques (DFD, ER, FSM, PN, etc.) into a Unified EnvironmentFSM, PN, etc.) into a Unified EnvironmentWhat Does a Modeling Language Provide?What Does a Modeling Language Provide?
Model Elements: Concepts and SemanticsNotation: Visual Rendering of Model ElementsGuidelines: Hints and Suggestions for Using Elements in Notation
UML has 13 Different Diagrams (2.0)UML has 13 Different Diagrams (2.0)References and ResourcesReferences and Resources
Web for UML 2.0: www.uml.org“The Unified Modeling Language Reference Manual”, Addison-Wesley.
CH5.110
CSE230
UML UseUML Use--Case DiagramsCase DiagramsDefine Functions on Basis of Actors and ActionsDefine Functions on Basis of Actors and Actions
borrow book
return book
library update
librariancustomer
56
CH5.111
CSE230
UML Sequence DiagramsUML Sequence DiagramsDescribe Object Interactions by Exchanging MessagesDescribe Object Interactions by Exchanging Messages
Librarian Catalogue
member card + book request membership
OK
book request
book available
book borrowed
Customer
CH5.112
CSE230
UML Sequence DiagramsUML Sequence DiagramsDescribe Object Interactions by Exchanging MessagesDescribe Object Interactions by Exchanging Messages
57
CH5.113
CSE230
UML Collaboration DiagramsUML Collaboration DiagramsObject Interactions and Their OrderingObject Interactions and Their Ordering
Customer Librarian Catalogue
1: member card + book request
2: membership OK
3: book request
4: book available 5: book borrowed
CH5.114
CSE230
UML UML StatechartStatechart DiagramsDiagramsAkin to Finite State MachineAkin to Finite State Machine
58
CH5.115
CSE230
Activity DiagramActivity DiagramAkin to Petri NetAkin to Petri Net
LetLet’’s Consider UML in Total (Jump to New s Consider UML in Total (Jump to New PowerPoint Presentation)PowerPoint Presentation)
CH5.116
CSE230
MathematicalMathematical--Based SpecificationsBased SpecificationsQueueingQueueing and Simulation Models and Simulation Models
Predict and Simulate System BehaviorCSE221
Declarative Specifications:Declarative Specifications:Logic SpecificationsAlgebraic SpecificationsCSE233 Programming Languages
Languages for Modular SpecificationsLanguages for Modular SpecificationsStatecharts and Z
