SEG 3550 Fundamentals of Information Systems

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SEG 3550Fundamentals of Information Systems

• Tutorial 1

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Outline

• Overview of DBMS
• Why use DBMS?
• History, Products
• Administrators and users
• Data Models
• Hierarchical Model
• Network Model
• Relational Model
• Object-Oriented Model

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Overview of DBMS

• Information processed data
• Database System Database DBMS
• Database Collection of interrelated data
• DBMS Set of programs to access the data
• Database Applications
• Banking all transactions
• Airlines reservations, schedules
• Universities registration, grades
• Sales customers, products, purchases
• Manufacturing production, inventory, orders,
  supply chain
• Human resources employee records, salaries, tax
  deductions
• Databases touch all aspects of our lives

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Advantages of DBMS

• Guarantee the ACID properties
• Atomicity prevents updates to the database
  occurring only partially
• Consistency guarantees there is no violation to
  any integrity constraints during the execution
• Isolation makes sure no operation outside the
  transaction can access the data in an
  intermediate state
• Durability guarantees the transactions that are
  successfully committed will survive permanently
  and will not be undone by system failure
• Efficient Data Access
• Great Processing Power
• Reduced Application Development Time

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Disadvantages of DBMS

• Difficult to learn
• Requires skilled administrators
• Expensive

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History

• Early 1960s (Network Data Model)
• Formed the basis of network data model (directed
  graph)
• Late 1960s (Hierarchical Data Model)
• Tree model
• Information Management System (IMS) by IBM
• 1970 (Relational Data Model)
• Idea is followed by the development of several
  DBMS (e.g., System R) and development of
  theoretical results.
• 1980s (RDBMS became a commercial standard)
• SQL was standardized as an RDBMS language

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History (cont)

• Late 1980s, the 1990s
• More complex queries
• Data warehouses, data mining
• Store and manage new data types. E.g., images,
  video
• Today
• XML is the widely used format for data exchange
  (tree model !)
• Publish XML data with a relational backend, store
  XML data into relational tables, and query the
  system regardless of how the underlying data is
  stored!

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Main DBMS Today

• Oracle
• IBMs DB2
• Microsoft SQL Server
• Sybase
• etc.
• FACT 1 The evolution of DBMS systems go hand in
  hand with research (IBM and Microsoft both have
  serious research laboratories).
• FACT 2 RDBMs is the main DBMS used by many
  companies nowadays and is a billion industry

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Database Administrator

• Coordinates all the activities of the database
  system the database administrator has a good
  understanding of the enterprises information
  resources and needs.
• Database administrator's duties include
• Schema definition
• Storage structure and access method definition
• Schema and physical organization modification
• Granting user authority to access the database
• Specifying integrity constraints
• Acting as liaison with users
• Monitoring performance and responding to changes
  in requirements

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Database Users

• Users are differentiated by the way they expect
  to interact with the system
• Application programmers interact with system
  through DML calls
• Sophisticated users form requests in a database
  query language
• Specialized users write specialized database
  applications that do not fit into the traditional
  data processing framework
• Naïve users invoke one of the permanent
  application programs that have been written
  previously

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Data Model

• A data model is a description of a container
  for data as well as a methodology for sorting and
  retrieving data from that container.
• Hierarchical, Network, Relational,
  Object-Orientated data model.

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Hierarchical Data Model

• Tree structure
• Data organization encoded in records
• One to many (or one to one) relationships
• Information retrieved by traversing the tree
• Advantages
• easy to search
• can add new braches easily
• Disadvantages
• data relationships are difficult to modify
• queries restricted to traversing the hierarchy

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Network Data Model

• Modification to the hierarchical model by adding
  circuits to the tree structure
• One-to-one, one-to-many, many-to-one or
  many-to-many relationships possible
• Advantages
• flexible, fast, efficient (less redundant
  information)
• Disadvantages
• complex
• restructuring can be difficult because of
  changing all pointers

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Relational Data Model

• Data application software functionality are
  separated
• A table is the main structure All data about a
  particular subject (person, place, thing or
  event) is stored in a table
• A field is used to store data in the database and
  represents a characteristic of the subject of the
  table in which it resides
• A record represents a unique instance of the
  subject of the table. It is composed of the
  entire set of fields in a table.
• A relationship is a connection established
  between a pair of tables.
• Four relationships one-to-one, one-to-many,
  many-to-one, many-to-many
• Advantages flexible in structure, supported by
  relational algebra, can represent complexity in
  relatively redundant free environment

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Relational Data Model (cont)
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Object-Oriented Data Model

• Data software application functionality are
  encapsulated together
• An objects data and functionality can be called
  upon and used by other objects

• An object is an instance of a class
• Objects are manipulated with methods, which are
  invoked by messages