MCS-032

1

UNIT – 1
INTRODUCTION TO OBJECT ORIENTED MODELING
Q1.
Ans:

What do you understand by Object Oriented Modeling?
Object oriented modeling is entirely a new way of thinking about problems. This
methodology is all about visualizing the things by using models organized around
real world concepts. Object oriented models help in understanding problems,
communicating with experts from a distance, modeling enterprises and designing
programs and database. Object oriented modeling is a language independent.

Q2.

Explain the processes that object oriented modeling passes through during
modeling.
Object oriented modeling passes through the following processes
 System Analysis
 System Design
 Object Design
 Final Implementation

Ans:

System Analysis
In this state a statement of the problem is formulated and a model is build by the
analyst in encouraging real world situation. The phase show the important
properties associated with the situation. In system analysis the objective is to
provide a model that can be understood and criticized by any application experts
in the area whether the expert is a programmer or not.
System Design
At this stage, the complete system architecture is designed. This is the stage where
the whole system is divided into sub-systems, based on both the system analysis
model and the proposed architecture of the system.
Object Design
In object design, a design model is developed based on the analysis model which
is already developed in the earlier phase of development. The object design
decides the data structures and algorithms needed to implement each of the
classes in the system with the help of implementation details given in the analysis
model.
Final Implementation
The final implementation of classes and relationships developed during object
design takes place a particular programming language, database, hardware
implementation, etc.

2
Q3.
Ans:

What are three kinds of models are in object oriented modeling?
The three kinds of models in object oriented modeling are object model, dynamic
model and functional model.
Object Model
Object models are used for describing the objects in the system and their
relationship among each other in the system.
Dynamic Model
Dynamic model describes the interaction among objects and information flow in
the system.
Functional Model
The functional model describes the data transformations in the system.

Q4.
Ans:

Explain the difference between structural approach and object oriented approach
in software development.
In structural approach, the main emphasis is on specifying and decomposing
system functionality. Structured approach is seen as the most direct way of
implementing a desired goal. A structured approach has certain basic problem
such as if the requirements of system change then a system based on decomposing
functionality may require massive restructuring and the system gradually becomes
unmanageable.
In contrast to structured approach, the basic focus of object oriented approach is
to identify objects from the application domain, and then to associate procedure or
methods around these identified objects. We can also say that object oriented
development is an indirect way of system development because in this approach,
a holistic view of application domain is considered and objects are identified in
the related problem domain. Taking holistic view of the problem domain rather
than considering function requirements of single problem give an edge to object
oriented development.

Q5.

Define the followings
(a)
Abstraction
The essential characteristics of an object that distinguish it from
all other kinds of objects and provide crisply-defined conceptual
boundaries relative to the perspective of the viewer is known as
abstraction.
(b)
Encapsulation
The process of compartmentalizing the elements of an
abstraction that constitute its structure and behavior;
encapsulation serves to separate the contractual interface of an
abstraction and its implementation.

3
(c)
Polymorphism
A concept in type theory, according to which a name (such as a
variable declaration) may denote objects of many different
classes that are related by some common super class; thus, any
object denoted by this name is able to respond to some common
set of operations in different ways.
(d)
Inheritance
Inheritance defines an "is-a" hierarchy among classes in which a
subclass inherits from one or more generalized super classes; a
subclass typically specializes its super classes by augmenting or
redefining existing structure and behavior. A relationship among
classes, wherein one class shares the structure or behavior
defined in one (single inheritance) or more (multiple inheritance)
other classes.
Q6.
Ans:

What is class and object?
A class is a set of objects that share a common structure and a
common behavior. The terms class and type are usually (but not
always) interchangeable; a class is a slightly different concept
than a type, in that it emphasizes the classification of structure
and behavior.
Each entity in the class is called object. An object has state,
behavior, and identity; the structure and behavior of similar
objects are defined in their common class. The terms instance
and object are interchangeable.

Q7. Define links.
Ans: A link is a physical or conceptual connection between objects. A
link is also defined as instance of an association.
Q8. Define multiplicity.
Ans: Multiplicity in an association specifies how many objects
participate in relationship. Multiplicity describes the number of
related objects. Multiplicity is generally explained as one or many
but in general it is a subset of the non-negative integers.
Q9. What is aggregation?
Ans: Aggregation is a special form of association, which models the
part-whole or a-part-of relationship as an aggregate the whole or
parts. The most considerable property of aggregation is
transitivity that is if x is part of y and y is part of z, then x is part
of z.
Q10. What is generalization?
Ans: Generalization is the relationship between a class, and it defines
a hierarchy of abstraction in which sub-classes one or more
inherit from one or more super-classes.

4
Q11. What are the advantages or benefits are of object oriented
modeling?
Ans: There are several advantages and benefits of object oriented
modeling which are given below:
(1)
Faster development
(2)
Increased quality
(3)
Easier maintenance
(4)
Reuse of software and designs, frameworks
(5)
Reduced
development
risks
for
complex
system
integration.
Q12. What is UML?
Ans: Unified Modeling Language (UML) is a well accepted language for
Object Oriented Analysis Design. It is used for visualizing,
specifying, constructing, and in final documentation. The basic
building blocks of UML used for Object Oriented Analysis and
Design are things, relationships, and diagrams.

%$%$%$%$Tuesday, December 04, 2007%$%$%$%$

5

UNIT – 2
OBJECT ORIENTED ANALYSIS
Q1.
Ans:

Define object identity. How can we create object identity?
Object identity is a property of an object that distinguishes the object from other
objects in the applications. In object oriented system, each object is given an
identity that will be permanently associated with the object irrespective of the
object’s structural or state transitions.
Object identity can be create in the following ways
1)
You can refer as memory address in programming languages.
2)
Assign identifier keys in the database.
3)
By user-specified names, used for both programming and database.

Q2.
Ans:

What do you understand by modularity?
Modularity is a way of mapping encapsulated abstractions into real, physical
modules. It is a property of a system that has been decomposed into cohesive and
loosely coupled modules.

Q3.
Ans:

What do you meant by typing? Differentiate between strong and weak typing.
The enforcement of the class of an object, which prevents
objects of different types from being interchanged or, at the
most, allows them to be interchanged only in very restricted
ways is called typing.
Strong Typing
When any operation upon an object which is defined can be
checked at compile time, i.e. type is confirmed forcefully is called
strong typing.
Weak Typing
In weak typing, operations on any object can be performed and
you can send any message to any class. Type confirmation is not
essential but in these types of language more errors at execution
time may occur.

Q4. Define concurrency and multi-threading.
Ans: The property that distinguishes an active object from one that is
not active is called concurrency. We can also say that
concurrency is handling more than one tasks at a time.
Within a program, the separately running pieces are called
threads and the concept of running many threads is called
multithreading.
Q5. Define persistency.
Ans: The property of an object by which its existence transcends time
i.e. the object continues to exist after its creator ceases to exist
is called persistency.

6
Q6.
Ans:

Compare and contrast object oriented analysis and structural
analysis.
Object Oriented Analysis
Object oriented analysis design is basically a bottom up approach which supports
viewing the system as a set of components that can be logically kept together to
form a system.
Advantages
i)
The object oriented approach inherently makes each object a stand alone
component that can be reused not only within specific problem domain but
also is completely different problem domains, having the requirement of
similar objects.
ii)
The other main advantage of object oriented is the focus on data
relationship.
Disadvantages
i)
But the disadvantage is that there is not place in the methodology to build
a complete functional model.
ii)
The object oriented models do not easily describe the communications
between objects.
Structural Analysis
Specifications in structural analysis is in the form of simple English language
statement and easier to understand. Therefore structural analysis provides a
natural way for discussing, modeling, and deriving the requirements of the
system.
Structural model do not readily support the use of reusable modules. The top
down process works well for new development, but does not provide the
mechanisms for designing in the use of existing components. The top down
process of functional decomposition does not lead to a set of requirements which
map well to existing components.

Q7.
Ans:

What do you meant by object modeling? What are the steps of designing object
modeling?
Object modeling means identifying objects and classes of a system or it describes
real world object classes and their relationships to each other.
The steps of object modeling are
i)
Identify objects
ii)
Create user object model diagram
iii)
Define user object attributes
iv)
Define user object actions
v)
Create action object matrix
vi)
Check for dynamic behavior
vii)
Review glossary

Q8.
Ans:

What is action-object matrix?
A matrix showing how update actions affect objects. It may be considered to be
part of the user object model, as it summarizes user object action definitions in a
tabular form.

7
Q9.
Ans:

What is dynamic modeling? What are the steps required for designing dynamic
modeling?
Dynamic modeling is a way of describing how an individual object responds to
events, either internal events triggered by other objects or external events
triggered by the outside world.
The steps required for dynamic modeling are given below:
i)
Analyze applicability of actions
ii)
Identify object states
iii)
Draw dynamic model diagram
iv)
Express each state in terms of object attributes
v)
Validate dynamic model
vi)
Concepts.

Q10.
Ans:

Ans:
Q12.
Ans:

Define
(a) State
An object may have one or more states – stable point in its life, expressed by the
object’s attributes and relationships.
(b) Events
Something that happens to an object. Atomic in that it either has happened or it
has not. An event causes an action.
What is functional modeling? Describe the steps in constructing functional
model.
Functional modeling describes the data transformations. Data model consists of a
number of processes which exchange information.
The steps in constructing functional model are:
i)
Identify input and output values
ii)
Build data flow diagrams showing functional dependencies
iii)
Describe functions
iv)
Identify constraints.
v)
Specify optimization criteria.

Q13.
Ans:

Differentiate between declarative description and procedural description.
A declarative description specifies the relationship between the input and output
values and relationship among output values.
A procedural description specifies a function by giving an algorithm to compute
it. The purpose of the algorithm is only to specify what the function does.

UNIT 3
USING UML
Q1.
Ans:

What are the major features of UML?
The major features of UML are given below:
1)
Defined system structure for object modeling
2)
Support for different model organization
3)
Strong modeling for structure and behavior
4)
Clear representation of concurrent activities

8
5)
Q2.
Ans:

Support for object oriented patterns for design reuse.

What are logical view and physical model?
The logical view of a system serves to describe the existence and meaning of the
key abstractions and the mechanism that form the problem space, or that define
the system architecture.
The physical model describes the concrete software and hardware components of
the system’s context or implementation.

Q3.
Ans:

Define use case?
A use case is a description of a set of sequence of actions that a system performs
to yield observable result that is of a value to an actor. The user is called actor and
the process is depicted by use case.

Q4.
Ans:

Define the following terms
Collaboration
Collaboration is a society of classes, interfaces and other elements that work
together to provide some cooperative behavior that is bigger than the sum of its
parts.
Dependency
Dependency is a relationship that states, that a change in specification of one
thing may affect another thing, but not necessary the reverse.
Generalization
Generalization is a relationship between general thing and a specific kind of thing.
It is also called “is a kind of” relationship.
Aggregation
Aggregation is a structural relationship that specifies that one class represents a
large thing which constitute of smaller things. It represents “has-a” relationship.

9
Q5.
Ans:

Explain the following structural diagrams.
(a)
Class Diagram
A class diagram is used to represent functional requirement of system. The class
diagram is used to model the vocabulary of the system, simple collaboration and
logical schema.
(b)
Object Diagram
An object diagram shows a set of object and their relationships at a point of time.
An object diagram is also used to model interactions that consist of objects that
collaborate without any message passed among them.
(c)
Component Diagram
A component diagram shows a set of component and their relationships. In a
dynamic model, a component diagram is used to model physical components such
as executable releases, libraries, databases, files or adaptable systems.
(d)
Deployment Diagram
A deployment diagrams shows all the nodes on the network, their
interconnections, and processor execution. In a dynamic model, a deployment
diagram is used to represent computational resources.

Q5.
Ans:

Explain the following behavioral diagrams.
(a)
Use Case Diagram
A use case diagram shows a set of use cases, actors and their relationships. The
diagram should be used to model the context or the requirement of a system. It
contains use cases, actors, dependency, generalization, association, relationships,
roles, constraints, packages and instances.
(b)
Interaction Diagram
An interaction diagram shows an interaction consisting of a set of objects and
their relationships, including the messages that may be dispatched among them.
These diagrams should be used to model the dynamic aspect of the system.
(c)
Sequence Diagram
A sequence diagrams are interaction diagrams that emphasize the time ordering of
messages. In UML it is shown as a table that shows object arranged along the xaxis and messages, ordered in increasing time, along the y-axis.
(b)
Collaboration Diagram
Collaboration diagrams are interaction diagrams that emphasize the structural
organization of an object that send and receive messages. There is always a path
in collaboration diagrams to indicate how one object is linked to another, and
sequence numbers to indicate the time ordering of a message.

10
(c)
Activity Diagram
Activity diagrams show the flow from one activity to another. An activity is an
ongoing non-atomic execution within a state machine. It contains activity states,
action states, transition states and objects.
(d)
State chart diagram
A state chart shows a state machine, emphasizing the flow of control from one
state to another. It contains simple states, composite states, transitions, events, and
actions.

+_+_+_+_+_+_+_+_+Tuesday, December 04, 2007+_+_+_+_+_+_+_+_+

11

UNIT – 1
SYSTEM DESIGN
Q1.
Ans:

What are the various steps in object oriented design process?
The various steps in object oriented design processes are given below:
i)
Define the context and modes of use of system
ii)
Designs the system architecture
iii)
Identifies the principal system objects.
iv)
Identify concurrency in the problem.
v)
Handling boundary conditions
vi)
Develops design models
vii)
Specifies object interface.

Q2.
Ans:

Compare and contrast process-oriented and object-oriented decomposition.
Process oriented decompositions divide a complex process, function or task into
simpler sub-processes until they are simple enough to be dealt with. The solutions
of these sub-functions then need to be executed in certain sequential or parallel
orders in order to obtain a solution to the complex process.
Object oriented decomposition aims at identifying individual autonomous objects
that encapsulate both a state and a certain behavior. Each major components of the
system is called a sub-system.

Q3.
Ans:

What are the advantages of object-oriented decomposition as compare to process
oriented decomposition?
Although both process-oriented and object-oriented decompositions deal with
complexity, we have reasons to believe that object oriented decomposition is
favorable because of the followings
i)
Object oriented approach provides for a semantically richer framework
that leads to decompositions that are more closely related to entities from
the real world.
ii)
Object oriented decompositions of systems tend to be better able to cope
with change.
iii)
Object oriented decompositions are closer to the problem domain, as they
directly represent the real world entities in their structure and behavior.
iv)
Object orientation has the advantage of continuity throughout analysis,
design implementation, and persistent representation.

Q4.
Ans:

Give the advantages of decompositions.
The advantages of decomposition are
1.
Separate people can work on each sub-system.
2.
An individual software engineer can specialize in a domain.
3.
Each individual component is smaller and therefore easier to understand
and manage.
4.
Part of the sub-system can be replaced or changed without having to
replace or extensively change other sub-systems.

Q5.

How is concurrency identified? How to death with concurrency?

12
Ans:

Concurrency in objects can be identified by the way they change state. Current
objects can change state independently. Aggregation implies concurrency in the
system.
Concurrency can be dealt by having the following keys.
i)
Develop a clear strategy for dealing with all concurrency issues during
system design.
ii)
Concurrency must be dealt with during the design process as dealing with
concurrency after the system is implemented is difficult.

Q6.
Ans:

What is the advantage of Database Management System for a data store?
The advantage of using a database management system for a data store is that
databases have mechanisms for describing data, managing persistent storage and
for providing a backup and recovery mechanism.

Q7.
Ans:

What are the issues to be considered while selecting database?
The issues to be considered while selecting database are
(i)
Storage space requirement: A database requires about triple the storage
space of actual data.
(ii)
Response time: The response time of the database for input or output
communication bound request.
(iii)
Locking modes pessimistic locking: Lock before accessing an object and
release when object access is complete.
(iv)
Optimistic locking: Read and write freely occurs.
(v)
Administration: Modern DBMS requires specially trained support staff to
set up security policies, manage the disk space, prepare backups, fine tune
the performance, and monitor performance.

Q8.

Differentiate between relational databases and object oriented databases.





Relational Database
Based on mathematical principles
called relational algebra.
Data are represented by a two
dimensional table with columns and
rows.
Implements standard query language
called SQL



Object Oriented Databases
Supports for complex objects.



Provides for mapping an object model
to an object oriented database.



Determine which objects are persistent.

13
Q8.
Ans:

What are the advantages and disadvantages of object oriented database?
Advantages of object oriented databases
 Support for complex objects.
 Provides for mapping of object model to an object oriented database.
 Determine which objects are persistent.
Disadvantages of object oriented databases
 Lacks rigorous theoretical foundation.
 Retrogressive to the old pointer systems.
 Lacks standard ad hoc query languages like SQL.
%^&$#@Tuesday, December 04, 2007@#$&^%

14

UNIT – 2
OBJECT DESIGN
Q1.
Ans:

Explain the three models and define their operations on classes.
The three models are explained below:
(a) Object Model
This describes the class of objects in the system, including their attributes, and the
operations that they support. The analysis object model information definitely
exists in some form in design. For this sometimes new redundant classes are
added which increase efficiency.
(b) Dynamic Model
The dynamic model describes how the system responds to external events. The
implementation of control of flow in a program must be realized either explicitly
or implicitly. Explicit means by the internal scheduler that recognizes events and
map them into operation calls. Implicit means by choosing algorithms that
perform the operations in a specified order.
(c) Functional Model
This defines the operation that the system must implement. For each operation,
from the analysis model must be assigned an algorithm that implements clearly
and efficiently, according to the optimization goals selected during system design.
In this model, we map the logical structure of the analysis model into a physical
organization of a program.

Q2.
Ans:

What are the object design steps?
The various steps required for object design are given below:
1.
Classify the operation on classes.
2.
Design an algorithm to implement operation.
3.
Optimization of data access paths.
4.
Implementing software control.
5.
Adjustment of inheritance
6.
Design of association.
7.
Determine object representation.
8.
Package classes and associations into models.

Q3.
Ans:

Explain the metrics for selecting the best algorithm.
There a number of metrics for selecting best algorithm which are given below:
(a)
Computational Complexity. The computational complexity includes time
complexity and space complexity.
(b)
Ease of use: A simple algorithm which is easy to implement and
understand can be used.
(c)
Flexibility: The fully optimized algorithm is generally less readable and
very difficult to implement.

Q4.
Ans:

What are the various steps for design optimization?
To optimize the design, the following things should be done:
1)
Adding redundant associations for efficient access.
2)
Rearranging the executing order for efficiency.

15
3)

Saving derived attributes to avoid re-computation.

Q5.
Ans:

Explain the technique for converting state diagram to code.
State diagram can be converted into code by using the following steps
i)
Identify the main control path, starting with the first state; find the path
from the diagram which corresponds to the expected sequence of events.
Keep the names of states in a linear sequence that now forms a sequence
of statements in the program.
ii)
Identify alternate path that branch off the main path and later join again.
These become conditional statements in the program.
iii)
Identify loops i.e. the backward paths branching off from main path, and
earlier. Multiple backward paths that not crossing over form nested loops.
iv)
Left out states transitions correspond to exceptional conditions which can
be talked by exception handling, or error routines, or even by setting and
testing of status flags.

Q6.
Ans:

Differentiate between one way associations and two way associations.
When an association is traversed in only one direction it is called one way
associations. It is implemented as a pointer i.e. an attribute that contains an object
reference. For example, teacher works for school.
When an association is traversed in both directions, although not usually with
equal frequency, are called two way associations.
&^%&^%&^%Tuesday, December 04, 2007&^%&^%&^%

16

UNIT – 3
ADVANCE OBJECT DESIGN
Q1.
Ans:

Define state event model.
State event model is a model which shows the sequence of events happening on
an object, and due to which there are changes in the state of an object.

Q2.
Ans:

What is state machine?
The state machine is an object but not an application object. It is part of the
language substrate to support the syntax of application object.

Q3.
Ans:

What is stub?
The minimal definition of a function or sub-routine without any internal code is
called stub.

Q4.
Ans:

How can we perform inheritance adjustment?
Inheritance adjustment can be done by using the following steps:
i)
Rearrange and adjust classes and operations to increase inheritance.
ii)
Abstract common behavior out of groups of classes.
iii)
Use delegation to share behavior when inheritance is semantically invited.

Q5.
Ans:

What do you understand by delegation?
Delegation consists of catching an operation on one object and sending it to
another object that is part, or related to the first object. In this process, only
meaningful operations are delegated to the second object, and meaningless
operations can be prevented from being inherited accidentally.
*&^%$*&^%$Tuesday, December 04, 2007*&^%$*&^%$

17

UNIT – 1
OBJECT MODELING
Q1.
Ans:

What do you understand by aggregation?
Aggregation is a stronger form of association. It represents the “has-a or part of”
relationship. An aggregation depicts a complex object that is composed of other
objects. We can also say that aggregation is special kind of association, adding
additional meaning in some situations. Two objects form an aggregation if they
are tightly connected by a whole-part relationship. In UML, it is represented as
Diamond Head.
Aggregation is not same as generalization. Generalization relates distinct classes
as a way of structuring a definition of a single object. A generalization defines
object as an instances of a super class and an instance of a subclass.

Q2.
Ans:

Define composition.
A stronger form of aggregation is called composition, which implies exclusive
ownership of the part of classes by the whole class. This means that parts may be
created after a composite is created but such parts will be explicitly removed
before the destruction of the composite.

Q3.
Ans:

What are the benefits of inheritance?
Inheritance gives you several benefits by letting you
 Reduce duplication by building on what you have created and debugged.
 Organize your classes in ways that match the real world situations and entities.

Q4.
Ans:

What is multiple inheritance?
Multiple inheritance allow a class to have more than one parent class and to
inherit features from all parents. Thus information may be mixed from multiple
sources. Multiple inheritance provides greater modeling power for defining
classes and enhance opportunities for reuse. By using multiple inheritance object
models can more closely reflect the structure and function of the real world.
Multiple inheritance facilitates the re-use existing classes much better single
inheritance.

Q5.
Ans:

What is generalization?
Generalization means extracting common properties from a collection of classes
and placing them higher in the inheritance in a super class. Generalization and
specialization are the reverse of each other. Specialization is a top down activity
that refines the abstract class into more concrete classes and generalization is a
bottom up activity that abstracts certain properties from existing classes, in order
to find more abstract classes.

18
Q6.
Ans:

What do you understand by metadata and keys?
Metadata is set of data which describes other data or a data used to describe a
class.
Object instances may be identified by an attribute called a key. A primary key is
an attribute that uniquely identifies an object instance and corresponds to the
identifier of an actual object.

Q7.
Ans:

What is domain integrity? Why domain is important?
A set of valid values for an attributes or a set of logical conceptual values from
which one or more attributes can draw their values is called domain. The rules
which define constraints on domain are called domain integrity.
Domain definitions are important because they
i)
Verify that attribute values makes business sense.
ii)
Determine whether two attributes occurrences of the same value really
represent the same real world value.
iii)
Determine whether various data manipulation operations makes business
sense.
Tuesday, December 04, 2007 

19

UNIT – 2
DYNAMIC MODELING
Q1.
Ans:

Define scenario?
A sequence of events that occurs during one particular execution of a system is
called scenario.

Q2.
Ans:

What is guard condition?
The guard condition is a Boolean expression written in terms of parameters of the
triggering event and attributes and links of the object that owns the state machine.
The guard condition may also involves tests of current states of the current
machine.

Q3.
Ans:

How is dynamic model represented?
The dynamic model is represented graphically by state diagrams. A state
corresponds to the interval between two events received by an object and
describes the value of the object for the time period.
%^$#$% Tuesday, December 04, 2007 %^$#$%

20

UNIT – 3
FUNCTIONAL MODELING
Q1.
Ans:

What do you understand by functional model?
The functional model specifies what happens, the dynamic model specifies when
it happens and the object model describes what it happens and the object model
describes what happens to an object.

Q2.
Ans:

What is data flow diagram?
A data flow diagram is a graph which shows the flow of data values from their
sources in objects through processes that transform them to their destinations in
other objects. A data flow diagram contains processes which transform data, data
flows which move data, actor objects which produce and consume data and the
data store object that store data passively.

Q3.
Ans:

Define process.
The term process means all the computation activities that are involved from the
input phase to the output phase. A process is represented with the ellipse symbol
and the name of process is written in it. Each process has a fixed number of input
and output data arrows, each of which carries a value of a given type.

Q4.
Ans:

What do you mean bys a data flow?
The term data flow literally means flow of data. A data flow connects the output
of an object or process to the input of another object or process. A data flow is
represented with the symbol arrow, and is used to connect the producer and the
consumer of the data type.

Q5.

Define the following
(a) Actors
The term actor means an object which can perform action. It is drawn as a
rectangle to show that it is an object.
(b) Data Store
The term data store literally means the place where data is stored. A data store is
represented by a pair of parallel lines containing the name of the store.
(c) Control Flow
A control flow is a Boolean value that affects whether a process is evaluated. The
control flow is not an input value to the process itself. It is shown by a dotted line
from a process producing a Boolean value to the process being controlled.

21
Q6.
Ans:

Define constraints? What are the different types of constrains?
A constraint shows the relationship between two objects at the same time, ore
between different values of the same object at different times. Object constraints
describe where some object depends entirely or partially on other objects.
Dynamic constraints represent relationship among the states or events of
different objects. Similarly, the functional constraints show the restrictions on
operations, such s the scaling transformations.

Q7.
Ans:

What are the limitations of data flow diagrams?
The limitations of data flow diagrams are given below:
(i)
The functional model does not specify when values are computed.
(ii)
The functional model does not specify how often values of an object are
computed.
(iii)
The functional model does not specify why the values of an object are
changes.
&^&%$ Tuesday, December 04, 2007 $%^&*

22

UNIT – 1
IMPLEMENTATION STRATEGIES
Q1.
Ans:

What do you understand by serialization? Where it is used and why?
Serialization is a generic term used for mechanisms that enable objects and object
structures to be converted into a portable form, removing the volatility created by
object addresses.
Serialization provides a convenient and straightforward way of making data
persistent. It is most appropriate when the amount of data involved is relatively
small. If large amounts of data are to be stored, serialization may no longer be
appropriate.

Q2.
Ans:

What is the difference between link and reference?
The basic difference between links and references is that links are symmetrical
whereas reference refers only to one direction. If two objects are linked, a single
link serves as a channel for sending messages in either direction. By using a
reference, however one object can send message to another, but the other object is
not aware of the object that is refereeing to it.

Q3.
Ans:

Discuss how the bi-directional implementations are made.
In a bi-directional implementation of an association, a pair of references should
implement each link. The declaration and code required to support such
implementations are same as needed in the unidirectional implementation. The
only difference is that suitable fields have to be declared in both classes
participating in the association.

Q4.
Ans:

What do you mean by persistence? How will you make your data persistent?
Persistent data is data, which has a longer lifetime than the program that created
it. Enabling data to be stored on a permanent storage medium provides
persistency. The most common techniques used are to store data is in the form of
files or make use of back-end database system.
)( )( )( )( )(Tuesday, December 04, 2007)( )( )( )( )(

23

UNIT – 2
OBJECT MAPPING WITH DATABASE
Q1.
Ans:

What are the two approaches to database design?
The two approaches of database design are:
Attribute Driven
Compile a list of attributes relevant to the application and normalize the groups of
attributes that preserve functional dependencies.
Entity Driven
Discover entities that are meaningful to the application and describe them.

Q2.
Ans:

Explain the database design layers?
The database design layers are explained below:
External Schema
External scheme provides an external view is an abstract representation of some
portion of the total database. An external schema is a definition of an external
view. Each external schema is a database design from the perspective of a single
application. The external schema isolates applications from most changes in the
conceptual schema.
Conceptual Schema
The conceptual view is a logical representation of the database in its entirely. The
conceptual schema is a definition of that conceptual view. It integrates related
applications and hides the details of the implementation of the underlying DBMS.
Internal Schema
The internal schema is the database as it is physically stored level schema is the
definition of the internal view. The internal schema level consists of actual DBMS
code required for the implementation of the conceptual schema.

Q3.
Ans:

What do you understand by primary key and foreign key?
A primary key is a combination of one, ore more attributes whose unique value
locates each row in a table. A foreign key is a primary key of one table that is
references in another table.

Q4.
Ans:

How object classes are map to tables?
Each object class maps to one or more tables in the database. The object in a class
may be partitioned horizontally and or vertically.
)(*)(*) (*)(*)(*)(Tuesday, December 04, 2007)(*)(*) (*)(*)(*)(