Module 2

• Data

  -relatively simple representation of more complex real-world data structures, usually graphical
• Data modeling

  • first step in the database design journey
  • serving as a bridge between real-world objects and the computer database. iterative, progressive process.
  • clarifies such communication by reducing complexities of database design to more easily understood abstractions that define entities, relations, and data transformations
• Model

  • abstraction of a more complex real-world object/event
  • helps understand the complexities of the real -world environment
• Blueprint

  • final data model
  • the instructions to build a database that will meet all end-user requirements.
  • narrative and graphical
  • contains both text descriptions in plain, unambiguous language and clear, helpful diagrams depicting the main data elements.
• DATA MODELS BASIC BUILDING BLOCKS

  1. Entity
  2. Attribute
  3. Relationship
  4. Constraint
• Entity

  -represents a particular type of object in the real world

  -distinguishable;such an entity is unique & distinct. person, place, thing or event about which data will be collected and stored.

  • Physical objects - customers,products
  • Abstractions - flight routes, musical concerts
• Physical objects

  -customers, products
• Abstractions

  -flight routes, musical concerts
• Attrubute

  -characteristic of an entity

  -equivalent of fields in the system

  • example: the identification of customers - last name, first name, phone number, address
• Relationship

  -describe an association among entities

  1. one-to-one (1:1 or 1..1)
  2. one-to-many (1:N or 1..*)
  3. many-to-many (N:N or *..*)
• Constraint

  -"must"

  -restriction placed on the data

  -ensure data integrity

  -expressed in the form of rules
• TYPES OF DATA MODELS

  1. Record Based Data Models (3)
  2. Object Based Data Models (4)
  3. Physical Data Models (2)
• Record Based Data Models

  -represent data by using the record structures

  1. Hierarchical Data Model
  2. Network Data Model
  3. Relational Model
• Hierarchical Data Model

  • organizes records in a tree structure
  • i.e., a hierarchy of parent and child records relationship
  • 2main concepts: Record and Parent-Child Relationship
• Network Data Model

  • permits a child record to have more than 1 parent,
  • directed graphs are used instead of a tree structure
  • a node can have more than 1 parent
  • 2 basic structures: Records (contains detailed information regarding the data which are classified into record types) and Sets
• Relational model

  • presents data in the form of tables which is used interchangeably each table consists of rows/tuples
  • Tuple/row: a collection of information about an item, e.g., student record), and a
  • column known as attributes.
• Object Based Data Models/Conceptual Models

  -define concepts, including entries, attributes, and relationships between them.

  -describe data at the logical and user view levels

  1. Entity Relationship Model
  2. Object-oriented Model
  3. Semantic Model
  4. Functional Model
• Entity-relationship (E-R) Model

  -shown diagrammatically using entity-relationship (E-R) diagrams representing the conceptual model elements

  -show the meanings and relationships between those elements independent of any particular DBMS.
• Object-oriented model

  -a logical data model

  -captures the semantics of objects supported in object-oriented programming

  -based on a collection of objects, attributes, and relationships that form static properties.

  -Object:collection of data and methods. When different objects of the same type are grouped together, they form a class.
• Semantic Data Models

  ‐used to express greater interdependencies among entities of interest.

  -developed to organize and represent knowledge but not data.
• Functional Data Model

  -describes aspects of a system concerned with transforming values-functions, mappings, constraints, and functional dependencies.

  -describes the computations within a system.
• Physical Data Models

  -provide the concepts that describe the details of how the data is stored in the computer along with their record structures, access paths, and order

  -Only specialized or professional users can use these models.

  1. Unifying model
  2. Frame memory model