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 # 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 S = F (RA A B S) Division • 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= R) A(R)- A( A(R) xS)- eNo E1 E2 E1 E4 pNo P1 P1 P3 P2 pName Bridge Bridge Tower Mosque pNo pName P1 Bridge P3 Tower budget 11.5m 11.5m 10.2m 9.1m budget 11.5m 10.2m R S Relational Calculus • Rather than how to obtain results, we say what the result is by specifying relationship between data • Based on first-order predicate logic • Expressed as { t | F(t)} 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 • Communication links carry data in form of Digital or analog signals • Each channel has a certain capacity • • • Modulation and Demodulation Multiplexing Mode of Operation Factors that Matter • Bandwidth • Mode of Operation • Software employed Header Text •Source Address •Destination Address •Message Number •Packet Number •Acknowledgement •Control Information Block Error Check Types of Networks Classification Criteria • Interconnection Structure • Transmission Mode • Geo Distribution Star 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 Broadcast Networks • Common channel utilized by all nodes • Message received by all, ownership checked • Multicasting • Generally Radio or Satellite based • Or Microwave Thanks ...In the previous lecture • Integrity Rules • Data Manipulation Languages In this Lecture • Derived Relational Algebra Ops… • Relational Calculus... Implementation: QBE Interface with Programming Languages • Tightly Coupled –Programming Language and database languages are merged • Loosely Coupled –PL is extended with special concepts Summary of