Relational and Object oriented database Management Systems

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Relational and Object oriented database Management Systems

What is the primary goal of DBMS?

The primary goal of DBMS is to provide an environment that is both convenient and efficient to use in retrieving and storing database information.

What is DBMS?

DBMS consists of a collection of interrelated data and a set of programs to access that data.

What are the levels of abstraction?

Physical level,conceptual level and view level.

Name some data models.

Object based logical model
Record based logical model
Physical data model

What is data independence?

The ability to modify a scheme definition in one level without affecting a scheme definition in the next higher level.

What is an entity?

An entity is an object that exists and is distinguishable from other objects.

What is relationship?

A relationship is an association among several entities.

8.What is mapping cardinalities?
It express the number of entities to which another entity can be associated
via a relationship set.

What is a superkey?

A superkey is a set of one or more attributes which taken collectively allow us to identify uniquely an entity in the entity set.

10.What is a weak entity set?
If we are not able to set the primary key, then the entity set is termed as
weak entity set.

11.What is aggregation?
Aggregation is an abstraction through which relationships are treated as
higher level entities.
12. What is a query language?
A query language is a language in which a user requests information from
the database.

13.List some fundamental operators in relational algebra
Select, project ,rename and natural join.

14. What is a tuple?
A row in a table.

15. Give any three unary operators.
Select, project and rename.

16. Give any three binary operators.
Union,Cartesian product and set difference.

17.What is object oriented?
It means that we organize software as a collection of discrete objects that
incorporate both data structure and behaviour.

18. Define Identity
It means that the data is quantized into discrete, distinguishable entities.

19.What is classification?
It means that objects with the same attributes and operations are grouped
into a class.

20. What is polymorphism?
It means that the same operation may behave differently on different
classes.

21. What is inheritance?
Inheritance is the sharing of attributes and operations among classes based
on a hierarchical relationship.

22. What are the stages in OMT?
Analysis, system design, object design and implementation.

23.What are the three models in OMT methodology?
Object model, dynamic model and functional model.

24. What is a dataflow diagram?
It is a graph whose nodes are processes and whose arcs are data flows.

25. What is a attribute?
An attribute is a data value held by the objects in a class.
26. Name the two types of object diagrams.
Class diagram and instance diagram

27. What is an operation?
An operation is a function or transformation that may be applied to or by
objects in a class.

28. What is a method?
A method is the implementation of operation for a class.

29. What is a link?
A link is a physical or conceptual connection between object instances.

30. What is an association?
An association describes a group of links with common structure and
common semantics.

What is a link attribute?

A link attribute is a property of the objects in a class.

32. What is a object diagram?
It is a graph whose nodes are object classes and whose arcs are
relationship among classes.

Define Multiplicity

Multiplicity specifies how many instances of one class may relate to a single instance of an associated class.

What is a role?

A role is one end of an association

What is a role name?

A role name is a name that uniquely identifies one end of an association.

What is state diagram

A state diagram relates events and states. It is a graph whose nodes are states and whose arcs are transition labeled by event names.

What is a state and an event?

A state is an abstraction of the attribute values and links of an object.
An event is something that happens at a point in time.

What is scenario?

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

What is data flow diagram?

A data flow diagram shows the functional relationship of the values computed by the system including input values,output values and internal data store. It is a graph showing the flow of data values from their sources in objects through process that tranform them to their destinations in other object.

What is a data store?

A data store is a passive object within a data flow diagram that stores data for later access.

What is abstract class?

A class that cannot have direct instances but whose descendants can have instances.

What is a candidate key?

A minimal set of attributes that uniquely identifies an instance or link.

Define event trace

It is a diagram that shows the sender and receiver of events and the sequence of events.

What is entity relationship diagram?

A graphical representation that shows entities and the relationship between them.

What is encapsulation?

A modeling and implementation technique that separates the external aspects of an object from the internal implementation details of the object.

What is dynamic model?

A description of aspects of a system concerned with control , including time, sequencing of operations and interaction of objects.

Define model

An abstraction of something for the purpose of understanding it before building it.

What is a schema?

The structure or template of the data in a database.

What is a view?

A virtual table that is derived from one or more underlying tables.

What is normalization?

Convert the tables into a standard form.

Name the transaction states.

Active
Partially committed
Failed
Aborted
Committed.

51.What are the fields in the log record?
Transaction name
Data item name
Old value
New value

What are phases in two phase locking protocol?

Growing phase
Shrinking phase

What is a deadlock?

It arrived at a state where neither of the transactions can ever proceed with its normal execution.

What is a transaction?

A transaction is a program unit that accesses and possibly updates various data items.

Define atomicity

All of the operations associated with a transaction must be executed to completion or none at all.

What are the two types of query language?

Procedural and Non procedural.

What is the condition for 1NF.

All the values should be atomic.

What is an activity?

An operation that takes time to complete. Activities are associated with states and represent real world accomplishments.

What is data dictionary?

A textual description of each class, its association, attributes and operations.

What is multiple inheritance?

A type of inheritance that permits a class to have more than one superclass and to inherit features from all ancestors.

What is override?

To define a method for an operation that replaces an inherited method for the same operation.

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