Download Public Management: Concepts and Big Questions

Data Structure &
File Systems
Hun Myoung Park, Ph.D.,
Public Management and Policy Analysis Program
Graduate School of International Relations
International University of Japan
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Outline
Traditional Data Approach
Database Approach
Database Schema
 External Schema
 Conceptual Schema
 Internal Schema
Relational Database
Relations and Primary Key
Database Management Systems
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Traditional Data Approach 1
One program/application/system and its
own data sets
Program-data dependency; data are tightly
tied to a program.
Program A  Data file a; Program B may not
access data file a that is specific to A.
Department C  Master data file c;
Department D may not use master data file c
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Traditional Data Approach 2
Data redundancy (duplication of data)
Lack of data integrity (accurate, consistent,
and up to date)
Limited data sharing
Lack of standardization in data structure and
access
Time consuming and costly development
and maintenance
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Database Approach
A data set shared by many programs and
systems
Program-data independence
Minimize data redundancy
Data integrity (consistency)
Data sharing and standardization
More complex and expensive
More risk in database management
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Database Applications
Distributed databases
Objective-oriented databases
Data warehousing
Online transaction processing (OLTP)
Online analytical processing (OLAP)
Data mining, business intelligence (BI)
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Database Management
Failure in database results in big loss
Data center and data grid
Database administrator (DBA)
Database management systems (DBMS)
Protect from natural disaster, misuse, or illegal
access (inside and outside)
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Types of Databases
Hierarchical database: tree structure, Rootparent-child levels records, one-to-many
relationship
Network database: each child record can
have more than on parent record.
Relational database: key field (identifier) to
link tables (relations)
Object-oriented databases: objects (data
and methods)
Database Schema
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Database Schema
Views of database structure (e.g., tables,
views, procedures, functions)
Described by a formal language in DBMS
(data dictionary).
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Types of Database Schema
Degrees of data abstraction
External schema: Users’ view
Conceptual schema: HW/SW independent
Internal schema: HW independent, SW
dependent)
Physical schema: HW/SW dependent
Users’ View
External Schema
(Application 1)
Overall View
DBMS View
External Schema
(Application 2)
Conceptual Schema
H/W independent
S/W independent
Internal Schema
H/W independent
S/W dependent
Physical Schema
H/W dependent
S/W dependent
External Schema
(Application 3)
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External Schema
External schema describes (end) users’ view
of databases
Represents a subset of the database
Multiple external schemas can exist
depending on applications
Ensure data security by limiting data access
to the subset of a database
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Conceptual Schema
Conceptual schema describes a global
views of the entire database
Integrate all external views
Basic blueprint of a database
Only one conceptual schema
ER-diagram represents this schema
Software/hardware independence
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Internal Schema
Internal schema is a representation of
conceptual schema from a specific DBMS’
view (not users’ view).
Hardware independent but software
dependent.
Logical independent if a internal schema is
changeable without touching its
corresponding conceptual schema
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Physical Schema
Physical schema describes how data are
actually stored on storage unit.
Dependent on DBMS, methods of accessing
files, types of hardware storage units, etc.
Physical independent if a physical schema
(model) is changeable without touching its
corresponding internal schema (model)
Relational Database
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Relational Database 1
A collection of tables.
A table (relation) consists of records each of
which consists of a list of related fields
Each table is related to other tables using
keys (primary and secondary keys)
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Relational Database 2



Table 



record 1 
record 2 
.............
record n 
field 1
field 2

field k
















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Relational Database 3
Table, relation, file, or object (entity set)
Record, tuple, entity (instance or
occurrence), or row
Field, attribute, or columns.
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Relational Database 4
Bit  Byte 
Field (dot) 
Record (line or 1st dimension) 
Table (plane or 2nd dimension) 
Database (cubic or 3rd dimension) 
Data Warehousing
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Attribute Types 1
Character (string)
Variable character
Integer (tiny, small): 1-2 bytes
Long integer
Float (decimal) 4 bytes
Double precession: 8 bytes
Numbers is preferred in terms of efficiency
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Attribute Types 2
Date/time
Logical or boolean (binary)
Text (memo)
Image/video/audio
Object, etc
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Variable Properties
Length of an attribute is determined by types
of data, and maximum length of data &
systems.
Allowable values and ranges (picture clause
in COBOL) are considered to improve data
quality and integrity
Relations and Primary Key
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Relations
Joining combines two or more tables
(relations)
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Primary Key
Primary key consists of one of more attributes
whose values uniquely identify a record in a
table.
To identify a unique record
No duplicate is allowed.
Secondary key
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Linking Tables Using Keys
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Joining Types 1
Joining combines two or more tables
(relations)
Inner (intersection of left and right tables)
Outer join (union of left and right)
Left (outer) join (first table as a reference)
Right (outer) join (second as reference)
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Joining Types 2
Left outer join: Include all entities in the left
table and entities in the right table matched
to any entity in the left table.
When the left table has A and B and the right
contains A and C, the left outer join produce
A, matched A (data items from the right
table), and B excluding C
Right outer join is the opposite to left outer
join (reference table is switched)
Database Management Systems
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DB Management System
Database management system (DBMS)
Controls the structure of a database and
access to the data.
Relational DBMS (RDBMS)
Object-oriented DBMS (OODBMS)
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DBMS Components 1
Data dictionary descries the structure of data
in databases such as name, type, length,
access control.
Utilities to create, modify, delete tables,
records, and fields.
Report generator
Access security, and system recovery
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DBMS Components 2
Query languages manipulate databases
Structured query language (SQL)
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DBMS Server







Oracle
DB2 (IBM)
SQL Server (Microsoft)
ASE (Adaptive Server Enterprise) and IQ
(Sybase  SAP)
Informix (InformixIBM)
Teradata (Teradata Co.)
Open source: MySql, PostgreSQL
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DBMS Client





dBase III (+), IV (Ashton TateBorland)
Clipper (programming language and
compiler for dBase III) (Nantucket Co.)
FoxBase (+), FoxPro, Visual FoxPro (Fox
SoftwareMicrosoft’s Visual Studio)
Paradox (Corel’s WordPerfect Office)
Access (Microsoft’s Office Suite) with zengine
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DBMS Service

Database as a Service (DaaS)
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Considerations
Data dictionary and E-R modeling
Attributes for the public sector
Performance measures
Data security: minimize use of private
information when designing conceptual
schemas, each department and application
has its own schemas
Database administrator’s role in ensuring
security in response to evolving threats.