1. Embedded Systems Software: Modeling and Programming--
The Object-oriented Paradigm
and
The Unified Modeling Language (UML)

2. Problems of software development
"problems" of software development (review):
**conceptual integrity
**incremental build, progressive refinement
**large projects "differ" from small ones
programming paradigms (1950’s-present): attempts to deal effectively with these problems, make software easier to develop and to maintain

3. A Brief History: Computer Hardware, Computer Languages, Design Techniques
1950's:unstructured, no information hiding--”spaghetti” code, GOTO, flowcharts
--machine code
--assembly lang.
--FORTRAN, LISP (Algol; COBOL)
1970s,1980s: structured, top-down design (“3 basic control structures, no GOTO”), modularity
--Pascal, C, PL/I, Ada
1990’s: encapsulation, information-hiding, reuse, hardware/software codesign (from
simulation languages developed much earlier, e.g., Modula, simula)
--C++, Java
2000’s: info hiding; web languages; environments encapsulating multiple
languages, styles
--.NET, C#, Python, Perl, MATLAB, Mathematica, Labview, …
Early machines—large, central (Eniac)
Supercomputers, “Minicomputers”, PCs, multiuser machines, PICs
Beowulf clusters, Spread of the Internet
“Ubiquitous computing”, laptops,.
Personal communication devices, multicore processors, GPUs
wpclipart.com
chilton-computing.org.uk
_microcontroller#History
techxav.com
cse.mtu.edu
visual.merriam-webster.com
43494A_QuadCore_Opt_Die_BLK_HRes.jpg textually.org

4. Important basic OO concepts: class: encapsulates data
OO class
Important basic OO concepts:
class: encapsulates data
structure (object) and associated methods (functions)
these may be declared public / private / protected
appropriate uses:
public: pass info to object or request info about object
(use "messages") (can be used by anyone)
private: modify object (can be used in class or by “friends”)
protected: for descendants (in class or by derived class and “friends”)

5. OO: class concept supports encapsulation, information hiding
Record/class
traditional: record (struct): functions to use or modify this record can be anywhere in the program
OO: class concept supports encapsulation, information hiding
OO Prog.
DATA
DATA
DATA
DATA
DATA
DATA
DATA
Procedural Prog.

6. wolf is carnivore; sheep is herbivore; grass is plant
Inheritance
Ex: Object data
structures:
A. Base class
B. Derived class X Y Z W X Y Z A. B.
Useful OO techniques:
Inheritance:
ex: in a program modeling an ecosystem, we might have the relationships:
wolf is carnivore; sheep is herbivore; grass is plant
carnivore is animal; herbivore is animal
animal is organism; plant is organism
here the base class “organism” holds data fields which apply to all organisms, e.g., amount of water needed to survive
two derived classes, plant and animal, hold information specific to each of these types of organisms, e.g., kind of soil preferred by plant
the animal class also has two derived classes, wolf and sheep
Inheritance allows the collection of common attributes and methods in "base" class and inclusion of more specific attributes and methods in derived classes

7. Polymorphism and overloading
base class can define a “virtual” function; appropriate versions of this function can be instantiated in each derived class (e.g., "draw" in the base class of graphical objects can have its own specific meaning for rectangles, lines, ellipses)
Overloading:
ex: cin >> num1;
>> is overloaded "shift”
ex: “+” can be overloaded to allow the addition of two vectors
ex: a function name can be overloaded to apply to more than one situation; e.g., a constructor can be defined one way if initial values are given and a different way if initial values are not given

8. template <class T> T method1 (T x) …..
Templates
Templates:
example:
template <class T>
T method1 (T x) …..
can be specialized: int method1 (int x)
float method1 (float y)
usertype method1 (usertype a)
templates promote reuse

9. Separate compilation:
Typically, an object-oriented program can be broken into three sets of components:
definitions and prototypes (text files, “header files”)
implementations (compiled--source code need not be available to user)
application program--uses the classes defined in header files and supported by the implementation files
This strategy promotes reuse and information hiding

10. Misuse of object-oriented paradigm
Note: no paradigm is misuse-proof

11. Design: “top-down”; Test: “bottom-up” : “Design for testability”
Using OO & (a subset of) UML in a project: design; design for testability
Design: “top-down”; Test: “bottom-up” : “Design for testability”
determine specifications:
use cases system tests
determine classes and connections (static behavior):
ER or class diagrams; CRC cards module (“black box”) tests
model dynamic behavior:
interaction (object message) diagrams
activity diagrams
state diagrams
sequence diagrams
[ individual class functions “white box” or “glass box” tests]
dynamic module interactions / “boundary” behavior

12. UML: a language for specifying and designing an OO project
UML: stands for "unified modeling language”
unifies methods of Booch, Rumbaugh (OMT or Object Modeling Technique), and Jacobson (OOSE or Object-Oriented Software Engineering)
mainly a modeling language, not a complete development method
Early versions -- second half of the 90's
Not all methods we will use are officially part of the UML description

13. an actual user can have many actor roles in these use cases
a part of the ”Unified Modeling Language" (UML) which we will use for requirements analysis and specification
each identifies a way the system will be used and the "actors" (people or devices) that will use it (an interaction between the user and the system)
each use case should capture some user-visible function and achieve some discrete goal for the user
an actual user can have many actor roles in these use cases
an instance of a use case is usually called a "scenario”
Use case will typically have graphical & verbal forms

14. Example use case
Example: cellular network place and receive calls use case (based on Booch, Rumbaugh, and Jacobson, The Unified Modeling Language User Guide)
Text description
--Use case name
(cellular network place
and receive calls)
--Participating actors
(cellular network and
human user)
--Flow of events
(network or user
accesses network to
use its functionality)
--Entry condition(s)
(user accesses
network using device
or password)
--Exit condition(s)
(call completed
lost or network busy)
--Quality requirements
(speed, service quality)
System boundary
Use case diagram—summarizes,
provides system overview
Text description—gives important details

15. Text description: Use case name Participating actors Flow of events
Entry condition(s)
Exit condition(s)
Quality requirements

16. Use case—detailed example (Pressman)
Example: “SAFEHOME” system (Pressman)
Use case: InitiateMonitoring
(Pressman text categories:
Primary actor (1)
Goal in context (2)
Preconditions (3)
Trigger (4)
Scenario (5)
Exceptions (6)
Priority (system development) (7)
When available (8)
Frequency of use (9)
Channel to actor (10)
Secondary actors (11)
Channels to secondary actors (12)
Open issues (13) )
Arms/disarms
system
Homeowner
Accesses system
via internet
Sensors
Responds to
alarm event
Encounters an
error condition
System administrator
Reconfigures
sensors
and related
system features
Pressman,
p. 163,
Figure 7.3

17. Use case—detailed example (Pressman)
Example: “SAFEHOME” system (Pressman)
Use case name: InitiateMonitoring
Participating actors: homeowner, technicians, sensors
Flow of events (homeowner):
--Homeowner wants to set the system when the homeowner leaves house or remains in house
--Homeowner observes control panel
--Homeowner enters password
--Homeowner selects “stay” or “away”
--Homeowner observes that read alarm light has come on, indicating the system is armed

18. Use detailed example (Pressman)--continued
Entry condition(s)
Homeowner decides to set control panel
Exit condition(s)
Control panel is not ready; homeowner must check all sensors and reset them if necessary
Control panel indicates incorrect password (one beep)—homeowner enters correct password
Password not recognized—must contact monitoring and response subsystem to reprogram password
Stay selected: control panel beeps twice and lights stay light; perimeter sensors are activated
Away selected: control panel beeps three times and lights away light; all sensors are activated

19. Use case—detailed example (Pressman)
Quality requirements:
Control panel may display additional text messages
time the homeowner has to enter the password from the time the first key is pressed
Ability to activate the system without the use of a password or with an abbreviated password
Ability to deactivate the system before it actually activates

20. Use case additions—simplifications of use case descriptions
A. Include: one use case includes another in its flow of events (cases A and B both include case C)
Extend: extend one use case to include additional behavior (cases D and E are extensions of case F)
<<include>> A C B
<<include>>
<<extend>> D F E
<<extend>>

21. Use case additions
C. Inheritance: one use case specializes the more general behavior of another G and H specialize behavior of J) G J
Authenticate with password
authenticate H
Authenticate with card

22. Examples: what would be a use case for:
Use case continued
Examples: what would be a use case for:
vending machine traffic light
Use case name
Participating actors
Flow of events
Entry condition
Exit condition
Quality requirements

23. Use cases can form a basis for system acceptance tests
System Tests
Note:
Use cases can form a basis for system acceptance tests
For each use case:
Develop one or more system tests to confirm that the use case requirements will be satisfied
Add explicit test values as soon as possible during design phase
These tests are now specifically tied to the use case and will be used as the top level acceptance tests
Do not forget use cases / tests for performance and usability requirements (these may be qualitative as well as quantitative)

24. Analysis model (UML version):
--functional model (use cases and scenarios)
--analysis object model (static: class and object diagrams)
--dynamic model (state and sequence diagrams)
As system is analyzed, specifications are refined and made more explicit; if necessary, requirements are also updated

25. Example: an activity diagram for analyzing a system you are building:

26. “Review”: use case: Graphical description:
Text description:
Use case name
Participating actors
Flow of events
Entry condition(s)
Exit condition(s)
Quality requirements
Arms/disarms
system
Homeowner
Accesses system
via internet
Sensors
Responds to
alarm event
Encounters an
error condition
System administrator
Reconfigures
sensors
and related
system features
Pressman,
p. 163,
Figure 7.3

27. “Review”: Use case writing guide:
--each use case should be traceable to requirements
--name should be a verb phrase to indicate user goal
--actor names should be noun phrases
--system boundary needs to be clearly defined
--use active voice in describing flow of events, to make clear who does what
--make sure the flow of events describes a complete user transaction
---if there is a dependence among steps, this needs to be made clear
--describe exceptions separately
--DO NOT describe the user interface to the system, only functions
--DO NOT make the use case too long—use extends, includes instead
--as you develop use cases, develop associated tests

28. Class and object diagrams:
Identify Objects from Use Case Specifications:
USE ENDUSER’s TERMS AS MUCH AS POSSIBLE
Entity objects: “things”, for example:
--nouns (customer, hospital, infection)
--real-world entities (resource, dispatcher)
--real-world activities to be tracked (evacuation_plan)
--data sources or sinks (printer)
Boundary objects: system interfaces, for example:
--controls (report(emergencybutton)
--forms (savings_deposit_form)
--messages (notify_of_error)
Control objects: usually one per use case
--coordinate boundary and entity objects in the use case
Use the identified objects in a sequence diagram to carry out the use case

29. tangible things, e.g., Mailbox, Document
Common classes
Other common types of classes which the developer can look for include:
tangible things, e.g., Mailbox, Document
system interfaces and devices, e.g., DisplayWindow, Input Reader
agents, e.g., Paginator, which computes document page breaks, or InputReader
events and transactions, e.g., MouseEvent,CustomerArrival
users and roles, e.g., Administrator, User
systems, e.g., mailsystem (overall), InitializationSystem (initializes)
containers, e.g., Mailbox, Invoice, Event
foundation classes, e.g., String, Date, Vector, etc.

30. a sequence diagram also models dynamic behavior
typically a sequence diagram shows how objects act together to implement a single use case
messages passed between the objects are also shown
sequence diagrams help to show the overall flow of control in the part of the program being modeled
they can also be used to show:
concurrent processes
asynchronous behavior

31. Sequence Diagram--Syntax
Objects in the sequence diagram are shown as boxes at the top
below each object is a dashed vertical line--the object’s “lifeline”
an arrow between two lifelines represents each message
arrows are labeled with message names and can also include information on arguments and control information
two types of control:
condition, e.g., [is greaterthan zero]
iteration, e.g., *[for all array items]
“return” arrows can also be included

32. Sequence Diagram Example

33. Useful object relationships
ER diagrams
Useful object relationships
These diagrams represent the relationships between the classes in the system. These represent a static view of the system.
There are three basic types of relationship:
inheritance ("is-a")
aggregation ("has-a”)
association ("uses")
These are commonly diagrammed as follows:

34. is-a: draw an arrow from the derived to the base class:
ER diagram: is-a
is-a: draw an arrow from the derived to the base class:
manager
employee

35. ER diagram--has-a
has-a: draw a line with a diamond on the end at the "container" class. Cardinalities may also be shown (1:1, 1:n, 1:0…m; 1:*, i.e., any number > 0, 1:1…*, i.e., any number > 1):
car
tire
tire & car can exist independently—shared aggregation
person
arm is part of the person– composition aggregation
arm

36. ER diagram--uses
uses or association: there are many ways to represent this relationship, e.g.,
employs 1
company
car
gasstation * * * n
employee 1
works for

37. CRC cards: class--responsibilities--collaborators cards
"responsibilities" = operators, methods
"collaborators" = related classes (for a particular
operator or method)
Make one actual card for each discovered class, with responsibilities and collaborators on the front, data fields on the back. CRC cards are not really part of UML, but are often used in conjunction with it.

38. CRC card--example
Example (based on Horstmann, Practical Object-Oriented Development in C++ and Java):
front back
Class Mailbox
Operations Relationships
(Responsibilities) (Collaborators)
get current message Message,
Messagequeue
play greeting
Class Mailbox
Queue of new messages
Queue of kept messages
Greeting
Extension number
Passcode

39. another way of adding detail to the design--models dynamic behavior
State Diagram
State Diagram:
another way of adding detail to the design--models dynamic behavior
describes all the possible states a particular object can be in and how that object's state changes as a result of events that affect that object
usually drawn for a single class to show behavior of a single object
used to clarify dynamic behavior within the system, as needed

40. State Diagram--Properties
A state diagram contains a "start" point, states, and transitions from one state to another.
Each state is labeled by its name and by the activities which occur when in that state.
Transitions can have three optional labels: Event [Guard] / Action.
A transition is triggered by an Event.
If there is no Event, then the transition is triggered as soon as the state activities are completed.
A Guard can be true or false. If the Guard is false, the transition is not taken.
An Action is completed during the transition.

41. State Diagram--Example
Example: this state diagram example for an "order" in an order-processing system is from Fowler and Scott, UML Distilled (Addison-Wesley, 1997):
start
/get first item
[not all items checked]
/get next item
[all items
checked &&
all items available]
Dispatching
Checking
initiate delivery
check item
[all items
checked &&
some items not in
stock]
delivered
item received
[all items in stock]
Delivered
Waiting
item received
[some items not in stock]

42. Example—bank simulation (Horstmann)
Horstmann, Mastering Object-Oriented Design in C++, Wiley, 1995
Teller 1
Teller 2
Customer 3
Customer 2
Customer 1
Teller 3
Teller 4

43. Example—bank simulation (Horstmann), cont.
An initial solution (Horstmann, p. 388):
Event
Departure
Arrival
Customer
Bank
EventQueue
Application
Bank Statistics

44. Example—bank simulation (Horstmann), cont.
An improved solution (Horstmann, p. 391):
Event
Departure
Arrival
Customer
Bank
EventQueue
Simulation
Bank Statistics

45. What simplifications have been made? Why? Comparison Bank Statistics
Event
Departure
Arrival
Customer
Bank
EventQueue
Application
Bank Statistics
What simplifications
have been made?
Why?
Event
Departure
Arrival
Customer
Bank
EventQueue
Simulation
Bank Statistics

46. Example:
How would we use the tools described so far to design a “smart” vending machine? How would we develop test cases at each stage?
Use cases?
Class diagram?
Sequence diagram?
Classes / CRC cards?

47. Software modeling for embedded systems: static and dynamic behavior

48. Important concepts in embedded systems:
--concurrency: the system can handle multiple active independent or cooperating objects at the same time
--thread [of control]—models sequential execution of a set of instructions; embedded system may have several concurrent threads operating simultaneously
--persistence—how long does a software object last?
Examples:
Temporary variable
Global variable
Software module

49. table_05_00 Recall: “UML” syntax can vary among implementations;
Previously we looked at one implementation, here we consider examples from the text
table_05_00
table_05_00

50. UML: Use case diagram (graphical)
fig_05_00
fig_05_00

51. UML Use case diagram--example
fig_05_01
fig_05_01

52. UML: Use case diagram (text); note exceptions
fig_05_02
fig_05_02

53. UML—static modeling

54. fig_05_03 UML: Class diagram (“CRC card”) Class name data Methods
(responsibilities
and
collaborators)
fig_05_03
(+ collaborators)
fig_05_03

55. UML: class relationships: inheritance
fig_05_04
fig_05_04

56. fig_05_05 UML: “interface”—similar to inheritance but different
public appearance
Hidden operation
fig_05_05
fig_05_05

57. fig_05_06 UML: containment of one class within another
Type 1: aggregation—statistical analysis has a number of algorithm “parts”
fig_05_06
fig_05_06

58. fig_05_07 UML: containment of one class within another
Type 2: composition—here the intervals are meaningless outside the schedule (~ “local variables”)
fig_05_07
fig_05_07

59. UML—dynamic modeling

60. UML: interaction diagram—call and return
fig_05_08
fig_05_08

61. UML: interaction diagram—create and destroy
fig_05_09
fig_05_09

62. fig_05_10 UML: interaction diagram—send (no response expected)

63. fig_05_11 UML: sequence diagram:
sequence of actions; carries out a use case
fig_05_11
fig_05_11

64. UML sequence diagram--example
fig_05_12
fig_05_12

65. UML: concurrent behavior. Example: fork and join
fig_05_13
fig_05_13

66. fig_05_14 UML: concurrent behavior. Example: branch and merge

67. UML activity diagram—captures all actions and control flows within a task
fig_05_15
fig_05_15

68. fig_05_16 UML state machine models--4 types of events:
UML state chart is a directed graph
fig_05_16
fig_05_16

69. fig_05_18 UML state chart: types of transitions initial state
final state
fig_05_18
fig_05_18

70. fig_05_19 UML state chart: actions and guard conditions
If guard condition is false, transition does not happen
fig_05_19
fig_05_19

71. UML: can decompose state into sequential substates
fig_05_20
fig_05_20

72. UML: can define a “history” state (e. g
UML: can define a “history” state (e.g., for an interrupt)—system will probably eventually return to this state
fig_05_21
fig_05_21

73. UML: can have concurrent substates
fig_05_22
fig_05_22

74. UML is a tool for a structured design methodology
It helps manage the design and development process
We can also look at modifying / refining the PROCESS itself
CMM : capability maturity model--defines level of the development process itself
1. Initial: ad hoc
2. Repeatable: basic project management processes in place
3. Defined: documented process integrated into an organization-wide software process
4. Managed: detailed measures are collected
5. Optimizing--desired level: Continuous process improvement from quantitative feedback

75. UML is a tool for a structured design methodology
It helps manage the design and development process
We can also look at modifying / refining the PROCESS itself
CMM : capability maturity model--defines level of the development process itself
1. Initial: ad hoc
2. Repeatable: basic project management processes in place
3. Defined: documented process integrated into an organization-wide software process
4. Managed: detailed measures are collected
5. Optimizing--desired level: Continuous process improvement from quantitative feedback

76. fig_05_23 Alternative methodology: control flow and data flow diagrams
(Note: in a processor we usually have a data path and a control path)
fig_05_23
fig_05_23

77. Control and data flow diagrams: tasks (with hierarchy levels)
fig_05_24
fig_05_24

78. fig_05_25 Control and data flow diagrams: Data sources and sinks

79. Control and data flow diagrams:
Data stores
fig_05_26
fig_05_26

80. Control and data flow diagrams:
Example
fig_05_27
fig_05_27

81. fig_05_28 Control and data flow diagrams:
Hierarchical view of an input / output task
fig_05_28
fig_05_28