1. Outline Data, Information & Knowledge Database DBMS Types of Models
E-R Model

2. Data, Information & Knowledge

3. Knowledge Knowledge is what we know helps us know where things are
It also contains our beliefs and expectations.
It is from this “map” that we base our decisions,
constantly updated
You can’t currently store knowledge in anything other than the brain
two sources that the brain uses to build this knowledge - information and data.

4. Data facts of the World description of the World.
We can perceive this data with our senses, and then the brain can process this.

5. Information knowledge was limited by our direct experiences.
can capture data in information, to be accessed at different times.
The information can be lost, but the data can’t be.

6. The infogineering model

7. Why does it matter that people mix them up ?
Data is always correct (I can’t be 29 years old and 62 years old at the same time)
but information can be wrong (there could be two files on me, one saying I was born in 1981, and one saying I was born in 1948).
Information captures data at a single point. The data changes over time.
Mistake : information is always an accurate reflection of the data.

8. Database Collection of data ?
not every collection of data is a database
An organized collection of related data
Eg ?

9. Why do we need a database?
Keep records of our:
Clients
Staff
Volunteers
To keep a record of activities and interventions;
Keep sales records;
Develop reports;
Perform research

10. DBMS
A software package/ system to facilitate the creation and maintenance of a computerized database.
A database's properties are determined by its supporting DBMS and vice-versa

11. Why DBMS ? Availability Efficient access Abstraction
Protection or Security measures to prevent unauthorized access
Reliable storage & recovery of 100s of GB
Querying/updating interface and API
Support for many concurrent users
Backup and recovery services.

12. What is the ultimate purpose of a database management system?
Is to transform
Data
Information
Knowledge
Action

13. Advancements Navigational pointers from one record to another.
eg: hierarchical model, Network model
Relational model
search for data by content,
rather than by following links
Entity-relationship model
to overcome the problems of Relational model as a modelling lang.
Object database and the XML database :
for multimedia, engg, documents etc.

14. Entity-Relationship Model
for representation of real-world
represents overall logical structure of information
grouping of data elements
inter-relationships between groups
simple and easy-to-use
permits top-down approach for controlling details
useful as a tool for communication between designer and user during requirements analysis and conceptual design

15. Core concepts Entity Entity set Strong entity type
Weak entity type ( discriminator / partial key)
Attributes
Simple and composite attributes
Single valued and multi valued attributes
Stored and derived attributes
Null attribute
Key attribute

16. Relationships
Degree
Cardinality
Mapping cardinalities
One to one
One to many
Many to one
Many to many

17. Participation constraints
Total participation
Partial participation
Keys
Super key
Candidate key
Primary key
Foreign key

18. Notations used in E-R Diagrams

21. Enhanced E-R

22. Contents
Why EER Modelling?
Inheritance
Specialization
Generalization

23. Why EER Modeling ? Emergence of new technologies
Semantic data modeling concepts

24. Inheritance Employee Sub class Super class Inheritance Secretary
Technician
Engineer
Manager
Clerk
Sub class
Super class
Inheritance

25. Specialization Define a set of subclasses of an entity type
Establish additional specific attributes with each sub class
Establish additional specific relationship types between each subclass and entity types or other sub classes

26. May have several specializations of the same superclass
The set of subclasses is based upon some distinguishing characteristics of the entities in the superclass
May have several specializations of the same superclass
{PERMANENT_EMPLOYEE, TEMPORARY_EMPLOYEE}
based on method of pay
{FACULTY, CLERK, TECHNICIAN}
based upon job type
specific attributes
Eg : TypingSpeed of SECRETARY
specific relationship types
Eg: HOURLY_EMPLOYEE can BELONG TO some TRADE UNIONs etc.

27. Example

28. Generalization Inverse process of specialization
Identify the common features of several entity types
Generalize them into a single super class
Eg : Employee is a generalization of {SECRETARY, ENGINEER, TECHNICIAN}

29. Example

30. CONSTRAINTS & CHARACTERISTICS OF SPECIALIZATION & GENERALIZATION

31. Outline Types of specialization Constraints on specialization
Specialization & Generalization
Hierarchies
Lattices
Summary

32. Types of Specialization (1/2)
Predicate defined
Condition specified
Conditions are specified on the values of some attributes in the superclass
Defining predicate
Eg: JobType = “Secretary”

33. Types Types of Specialization (2/2) (1/2)
Attribute defined
If all subclasses in a specialization have membership condition on same attribute of the superclass
Defining attribute
Eg: JobType
User Defined
No condition for determining the membership of the subclass
Specified individually for each entity by the user

34. Example Job Type Defining attribute Defining predicate “Technician”
“Secretary”
“Engineer”

35. Constraints on specialization
Disjointness Constraint
Subclasses of the specialization must be disjoint
An entity can be a member of at most one of the subclasses of the specialization
Not disjoint  Overlap
Notation d O
Disjointness
Overlapping

36. Disjoint Rule
A patient can either be outpatient or resident, but not both

37. Overlap rule
A part may be both purchased and manufactured

38. Constraints on specialization
Completeness Constraint
Total
every entity in the superclass must be a member of some subclass in the specialization/ generalization
Shown in EER diagrams by a double line
Eg: Employee {Hourly_Employee, Salaried_Employee}
Partial
allows an entity not to belong to any of the subclasses
Shown in EER diagrams by a single line
Eg: Employee need not be {Secretary, Technician, Engineer}

39. Total Specialization A patient must be either an outpatient
or a resident patient

40. Partial Specialization
A vehicle could be a car,
a truck, or neither

41. Specialization Hierarchy & Lattice
Every subclass has only one superclass
single inheritance
Lattice:
A subclass can be subclass of more than one superclass
multiple inheritance
Same for generalization hierarchies or lattices
Shared subclass:
A subclass with more than one superclass

42. Example

43. Note
In a lattice or hierarchy, a subclass inherits attributes not only of its direct superclass, but also of all its predecessor superclasses
Specialization  top down approach
Generalization  bottom up approach
In practice, the combination of two processes is employed

44. Relationships of degree higher than two

45. Outline Binary or ternary relationships ?
Constraints on n-ary relationships
Aggregation
Union / Category

46. Binary or ternary relationships ?
On the basis of semantics of the situation
Supply
Project
Supplier
Part

47. Dividing into 3 binary relations
Supplies
Project
Supplier
Uses
Can supply
Part

48. Solution 1:
Include the ternary relationship + 1 or more of the binary relationships (if they rep. diff. meanings & if all are needed for the appln.)
Solution 2:
Represent the ternary relationship as weak entity type with NO partial key & identifying relationships.

49. Constraints on n-ary relationships
Cardinality Ratio Notation
1, M, N
Min, Max Notation

50. Aggregation ER Model can’t represent relationships among relationships
To represent relationship between a whole object & its component parts
Relationships are treated as higher level entities

51. Example CAR Other Systems Chassis Drive-train (steel frame) Wheels
Hub-Caps
Tires
Tubes
represents IS-PART-OF (component) relationship
Root class: CAR
Component Classes: Chassis, Drive-Train, Other Systems, Wheels
Root class: Wheels
Component Classes: Tires, Tubes, Hub-Caps

52. Consider the ternary relationship works-on,

53. Suppose we want to record managers for tasks performed by an employee at a branch

54. E-R Diagram With Aggregation

55. Union / Category Engineering_Manager Engineer Manager
 Salaried Employee
Need to model a single superclass/subclass relationship with more than one superclass
 subclass = collection of objects i.e. a subset of the “union” of distinct entity types

56. Example:

57. subset of the intersection of its superclasses
Shared Sub class
Category
subset of the intersection of its superclasses
shared subclass member must exist in all of its superclasses
Attribute Inheritance :
Total
subset of the union of its superclasses
category member must exist in any of its superclasses
Attribute Inheritance :
Selective

58. THANK YOU !!!