Shared Flashcard Set

Details

DBMS Chapter 3 Part 2
Relational and UML Models
44
Other
Graduate
01/11/2015
Click here to study/print these flashcards.

Create your own flash cards! Sign up here.

Additional Other Flashcards

 

 

Cards

Term
Relation Model
 Definition
Formal model with a sound mathematical foundation based on set theory and first order predicate logic with no graphical representation.
Term
Relation
 Definition
collection of tuples that each represent a similar real world entity
Term
Tuple
 Definition
an ordered list of values that each describe an aspect of an entity
Term
Primary key
 Definition
uniquely defines a tuple
Term
Foreign Keys
 Definition
Interrelate tuples and references a primary key in another relation
Term
Relation Schema
 Definition
R(A1,A2,A3...) R being the relation name and A being an attribute
Term
Characteristics of Relations
 Definition
  • There is no logical ordering of tubles in a relation
  • There is an ordering to the values within a tuple
  • Each attribute is single valued and atomi
  • A null value corresponts to unknown or inapplicable
Term
Relational Constraints
 Definition
  • Domain constraints
  • key contraints
  • entity integrity, not null constraints 
  • referential integrity constraints 
  • semantic integrity constraints
Term
Domain Constraint
 Definition
Value of each atrribute A must be an atomic value from the domain dom(A)
Term
Key Constraint
 Definition
  • All tuples must be unique
  • Every tuple has at least on default superkey(set of all atributes)
  • No two can have same value for super key
Term
Superykey
 Definition
subset of attributes that uniquely identify a tuple
Term
Key
 Definition
Uniquely identifies a tuple with minimal attributes(no redundent attributes)
Term
Candidate key
 Definition
when a relation schema has more than one key that can be used to uniquely identify it, one is chosen to be primary key
Term
Not Null Constraint
 Definition
  • specifies an attribute cannot be null 
  • primary keys can never be null (entity integrity constaints)
Term
Semantic Integrity Contraints
 Definition
  • General contraints that cant be enforced by normal relational model
  • e.g employee should always work in department he/she manages
Term
Insertion anomoly
 Definition
difficult to insert new things into model
Term
Deletion Anomaly
 Definition
deleting something will delete entity type
Term
Modification Anomaly
 Definition
if you update one thing you must update all manually
Term
Functional Dependency
 Definition
means an attribute depends on another
Term
Prime attribute
 Definition
attribute that is part of any candidate key
Term
Normalisation of Data
 Definition
process of analysing relation schema based on functional dependency and candite keys to minimize redunancies and anomalies
Term
First Normal Form(1NF)
 Definition
  1. Domain of the attribute must include only atomic values and any attribute in the tuple must be a single value from the domain
  2. if not true remove attribute and place in seperate relation with primary key of the original relation
  3. Remove nest relation attribute and take the primary key into it
  4. NO COMPOSITE OR MULTIVALUED ATTRIBUTES

(DNUMBER, DLOCATION, DMGRSSN)

                            1NF

(DNUMBER, DLOCATION)

(DNUMBER,DMGRSSN)


Assumptions: 

 a department can have multiple locations!

 multiple departments are possible at a given location!

 
Term
Second Normal Form(2NF)
 Definition
  • Relation schema R is in 2NF if it satisfies 1NF and every nonprime attribute A in R is fully functional dependent on any key of R
  • If not decompose and make a new relation for each partical key with its dependent attributes

(SSN, PNUMBER, PNAME, HOURS)

                            2NF

(PNUMBER, PNAME)

(SSN, PNUMBER, HOURS)
Term
Full functional dependency
 Definition

if removal of any attribute A from X means that the dependency doesn not hold anymore 

SSN, PNUMBER --> HOURS

PNUMBER --> PNAME
Term
partial dependency
 Definition

jf some atribute can be removed from X and the dependency still holds

e.g.

SSN,PNUMBER-->PNAME
Term
Third Normal form(3NF)
 Definition
  • A relation schema is in 3NF if it satisfies 2NF and no nonprime attribute of R is transitively dependent on the primary key
  • if not decompose and set up r that inclused the nonkey attributes that functionally determene other non key attributes

(SSN, ENAME, DNUMBER, DNAME, DMGRSSN) 

                      3NF

(SSN, ENAME, DNUMBER)

(DNUMBER, DNAME, DMGRSSN) 
Term
Transitive dependency
 Definition
a set of attributes Z that is neither a candidate nor a subset of any key of R, and both X->Z abd Z->Y hold
Term
Boyce-Codd Normal Form(BCNF)
 Definition

if for every one of its non-trivial functional dependencies X-->Y, X is a superkey-that is, X is either a candidate key or a superset thereof

Supplier (SNR, SNAME, PRODNR, QUANTITY)

        Superkey {SNR, PRODNR}  and   superkey {SNAME, PRODNR}

        SNR --> SNAME   and   SNAME -->SNR 

                  BCNF

SupplierBCNF 1 (SNR, SNAME)                           RBCNF 1 (SNR, SNAME)

SupplierBCNF 2 (SNR, PRODNR, QUANTITY)     RBCNF 2 (SNAME, PRODNR, QUANTITY) 
Term
Trival functional dependency
 Definition
X-->Y is trivial if Y is a subset of X
Term
Fourth Normal Form
 Definition

for every one of its non-trivial multivalued dependencies X->->Y,X is  a super key - that is, X is either a candidate key or a superset thereof

 

(course, instructor, textbook)

One course is taught by different instructors

One course uses the same set of textbooks by each instructor

(course, textbook)

(course, instructor)
Term
multi-valued dependency
 Definition
from X to Y X->->y if and only if each X value exactly determines a set of Y values, independently of other attributes
Term
Polymorphism/overloading
 Definition
access different object through uniform interface
Term
Dynamic Binding
 Definition
exact implementation of the function call depends on the function call and the receiving object
Term
OODBMS
 Definition
  • in OOPL(transient objects)
  • make object persistet
  • dependent on programming langauge
  • need for standards
  • not succesful 
Term
Associations
 Definition
  • *
  • 0..1
  • 1..*
  • 1
Term
Qualified Associations
 Definition
  • the qualifier specifies 1 or more attributes that are used as index key for navigationg from the qualified class to the target class
  • reduces multiplicity 
Term
Weak Entity types(UML)
 Definition
  • Uses qualified associations
  • Attach partial key to owner class
Term
Aggregation(UML)
 Definition
  • Composite object composed using part objects
Term
Composite aggregation
 Definition
  • part object can only belong to one composite
  • maximum cardinality at composite side is 1
  • part object is removed when composite is removed
Term
Shared Aggregation
 Definition
  • Part object can belong to multiple composite objects
  • maximum cardinality at composite side is undetermined 
  • part object can also occur without belonging to composite
Term
Structural Limitations of the UML
 Definition
  • Not many 
  • has changeability property
Supporting users have an ad free experience!