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CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
APR2016
ASSESSMENT_CODE MCA3020_APR2016
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
18253
QUESTION_TEXT
Explain Temporal Database and Multimedia Database.
SCHEME OF
EVALUATION
Temporal Database: Temporal databases are used to record timereferenced data. Basically, majority of the database technologies are
temporal. For example: Record keeping function (inventory
administration, medical-record and personnel); Financial function
(banking, accounting and portfolio organization); Scientific function
(Weather monitoring), Scheduling function (project organization, hotel,
airline, and train reservations) all these functions trust on temporal
databases. (2 marks)
Temporal databases are best suited for the applications where
information as to organize on time constraints. Therefore temporal
database set a good example to demonstrate the requirement for
development of a combined set of concepts for the use of application
developers. The training of temporal database is designed by application
developers and designers. There are numerous applications where time is
an important factor in storing the information. For example: Insurance,
Healthcare, Reservation Systems, and Scientific Databases. (2 marks)
In case of temporal applications, even the two instances utilized might be
simply expanded. For example, in COMPANY database, it might be
desirable to keep PROJECT, JOB, and SALARY histories of all the
employees. It can be applied to UNIVERSITY database as well, to store
the grade history of STUDENT. The details about the YEAR,
SEMESTER, COURSE and each SECTION are also included in this
database.(1 mark)
Multimedia Database: Multimedia databases facilitate the users to store
as well as generate query for retrieving multimedia information. This
information can demand for: Documents (like articles/books/journals),
Images (like drawings/pictures), Video Clips (like
newsreels/movies/hone videos); Audio clips (like speeches/ phone
messages/ songs).(1 mark)
The primary type of database query generally tries to locate multimedia
sources comprising of particular objects of interest. Such as, one user
wants to locate all the video clips regarding aa specific person, say
Michael Jackson in a video database. Another scenario may be as of
someone willing to retrieve video clips grounded on specific activities
like, video clips where a soccer goal is scored by a certain player or
team. These type of queries are mentioned as content based retrieval, as
they retrieve information bases on a certain activity/object from the
multimedia sources.
(2 marks)
To make this retrieval fast, the multimedia database must make use of
some model to index and manage multimedia sources grounded on the
contents. But identifying the contents of multimedia sources is lengthy
and difficult task. To accomplish this task, two approaches can be
followed as defined below:
1.Based on automatic analysis of the multimedia sources. It is done to
recognize the contents mathematical characteristics.
2.Based on manual identification of the objects and objectives of interest
in each multimedia source. And later on depending on this information
index the sources.
(2 marks)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
73629
QUESTION_TEXT
What are the different models of DBMS? State two advantages of each
type.
SCHEME OF
EVALUATION
5 models with advantages - >2 marks each. Any two advantages among
those mentioned below may be written
Hierarchical
Simplicity (simple design process since data consists of hierarchical
relationship), Security (can execute the changing level of security
characteristics), Database integrity (possible due to inbuilt structure of
parent and child), Relationship handling (proficient for relationships of
the type 1:M)
Network
Simplicity (simple design process since instances of data relationship
occur as N:M type), Flexibility (more flexible as you can navigate data
items in many ways), Standards (include development of worldwide
standards), Relationship handling (proficient for relationships of the
type N:M – popular in real data relationship situations)
Relational
Simplicity simple design process since easy to handle RDBMS), Flexibility
(more flexibity), Follow every mathematical theory (obeys theories in
maths), Relationship handling (can handle any every type of
relationship)
Object relational
Reusability (occurs from reuse and sharing), Flexibility (flexible but not
more flexible than RDBMS), Abstraction (permits developers of
software to incorporate their individual types and techniques applied to
DBMS), Relationship managing (helps in gathering records effortlessly)
Object
Relationship handling (can handle any every type of relationship), Use
of navigational interfaces – hence better than other models
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
125268
QUESTION_TEXT
Define transaction. Explain their properties.
Definition – 2 marks
4 properties – 2 marks each
Transaction is a logical unit of data manipulation related tasks wherein
either all the component tasks must be completed or none of them is
executed in order to keep the database consistent.
ACID properties
SCHEME OF
EVALUATION
Atomicity – Either every operation is executed in a successful manner
or none of them is executed at all.
Consistency – database integrity rules must be obeyed properly
Isolation – assurance that all transactions are executed independently
even in a multitransaction environment
Durability – changes performed in the database are saved in physical
database once the transaction is over.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
125269
QUESTION_TEXT
What is denormalization? Explain its techniques.
Definition – 2 marks
each
SCHEME OF
EVALUATION
4 techniques – 2 marks
Denormalization is the process of converting higher normal norms to
lower normal forms with the objective of getting faster access to
database.
(a) Duplicate data – method of adding duplicate data into relational
table. This will minimize the number of joins required to execute a given
query. It also minimizes the CPU and I/O resources being utilized as
well as boosts up the performance
(b) Summary data – records are summarized in some summary
columns thereby reducing the number of records stored in a table. This
enhances database performance as now the database server needs to
process lesser records for a given query execution
(c) Horizontal partitioning – table is split by rows thereby reducing the
number of records paer table and hence drives the performance
(d) Vertical fragmentation – breaks relations by columns. It makes
more than 2 tables by allocating the original key to all and allocating a
few of the non key columns to every newly made identical keyed table
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
125271
QUESTION_TEXT
Differentiate between BCNF and 3 NF.
Comparison of BCNF and 3NF
We have seen BCNF and 3NF.
It is always possible to obtain a 3NF design without sacrificing losslessjoin or dependency-preservation.
If we do not eliminate all transitive dependencies, we may need to use
null values to represent some of the meaningful relationships.
Repetition of information occurs.
SCHEME OF
EVALUATION
These problems can be illustrated with Banker-schema.
As banker-name bname , we may want to express relationships
between a banker and his or her branch.
Figure : An instance of Banker-schema.
Figure shows how we must either have a corresponding value for
customer name, or include a null.
Repetition of information also occurs.
Every occurrence of the banker's name must be accompanied by the
branch name.
If we must choose between BCNF and dependency preservation, it is
generally better to opt for 3NF.
If we cannot check for dependency preservation efficiently, we either
pay a high price in system performance or risk the integrity of the data.
The limited amount of redundancy in 3NF is then a lesser evil.
To summarize, our goal for a relational database design is
BCNF.
Lossless-join.
Dependency-preservation.
If we cannot achieve this, we accept
3NF
Lossless-join.
Dependency-preservation.
A final point: there is a price to pay for decomposition. When we
decompose a relation, we have to use natural joins or Cartesian products
to put the pieces back together. This takes computational time.
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
125275
QUESTION_TEXT
Discuss Semantic Query Optimization. What are the various Execution
Strategies for SQL Sub Queries?
SCHEME OF
EVALUATION
Semantic Query Execution: Semantic Query Execution is a technique to
modify one query into another query by using the relational database
constraints. These constraints may be unique attributes or much more
complex constraints. This technique is used for the efficient execution of
the query.
(1 mark)
Consider the example below:
Select E.LNAME, M.LNAME
FROM EMPLOYEE AS E, EMPLOYEE AS M
WHERE E.SUPERNO=M.ENO AND E.SALARY>M.SALARY
marks)
(2
This query retrieves the names of employees who earn more than their
supervisors. If a constraint is applied on the database schema to check
that none of the employee can earn more than his reporting supervisor;
the semantic query optimizer checks for this constraint and may not
execute the query if it knows that the resultant query will be empty. If
the constraint check is done efficiently then this approach can save a lot
of time.
(2 marks)
Execution Strategies for SQL Sub Queries: Different physical execution
strategies are employed by query optimizer for the various logical query
plan options. Two types of strategies are there for sub query execution:
1.
Navigational Strategies
2.
Set-Oriented Processing
(1 mark)
1.
Navigational Strategies: For executing sub-query, navigational
strategies depends on the nested loops joins. Basically there are two
classes of navigational strategies: forward lookup and reverse lookup.
Forward lookup firstly starts executing the outer query and when outer
rows are generated then it invokes the sub-query. Reverse lookup starts
with the sub-query and processes one sub-query row at a
time.
(2 marks)
2.
Set-Oriented Processing: Set-Oriented Processing finally needs that
the query could be effectively de-correlated. If this is the situation, set
operations for example hash, merge and join can execute the
query.
(2 marks)