Distributed Database Management Systems: Lecture 8

Distributed Database Management Systems: Lecture 8. The main topics covered in this chapter include: derived relational algebra ops; relational calculus; semi join; first-order predicate logic; atomic formula;...

Distributed Database Management Systems

Lecture # 8

In the previous lecture

• Integrity Rules

• Data Manipulation Languages

In this Lecture

• Derived Relational Algebra

Ops…

• Relational Calculus

Semi join

• Subset of tuples of R that

participate in join of R with S

R F S = A(RA S)

B

• The division of R with degree r

with S with degree s is the set of (r-s)-tuples t such that

for all s-tuples u in , the tuple tu is

in R.

R S = A(R)- A( A(R)

xS)-R)

eNo pNo pName budget

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P1

P3

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11.5m 10.2m

R

S

Relational Calculus

• Rather than how to obtain

results, we say what the result

Find the set of all tuples t such that F(t) is true, where F

implies the predicate condition

Atomic Formula

• Tuple-variable membership

expression: specified as R(t) or R.t

• Conditions

–s[A] Θ t[B]

–S[A] Θ c

• Language based on

Tuple-oriented Calculs……?

• Select EMP.eName,

DEP.dName from EMP, DEP where EMP.dNo = DEP.dNo

Domain Relational Calculus

• Domain variable ranges over

values in a domain and specifies

Interface with Programming Languages

• Tightly Coupled

–Programming Language and

database languages are

merged

• Loosely Coupled

–PL is extended with special

concepts

Computer Networks

A computer network is a

system for communication between two or more

computers

• Computers are called Nodes,

sites, hosts

• Other equipment at nodes

• Equipment connected via links

and channels

Data Communication

• Communication links carry

data in form of Digital or

Factors that Matter

• Bandwidth

• Mode of Operation

• Software employed

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Check Text

Types of Networks

Classification Criteria

• Interconnection Structure

• Transmission Mode

• Geo Distribution

Central Control Node

Ring Network

Unidirectional

Ring

Ring Interface

Bus Network

BUS

Meshed Network

Transmission

Mode

• Point to Point (uni cast)

• Broadcast (multi-point

networks)

Point to Point

• One or more links between

sender and receiver

• Link may be direct or through

switching

• Multicasting

• Generally Radio or Satellite

based

• Or Microwave

Thanks