Chapter 14: ObjectOriented Modeling

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Chapter 14 Object-Oriented Modeling

• MIS 2403-Data Base Management
• McFadden, Hoffer Prescott text
• Dr. Segall - Chapter 14

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Object-Oriented Data Modeling

• Merger of two fields
• Data and Process Modeling
• Object-oriented programming languages
• SmallTalk C Visual Basic Micro-Focus COBOL
  Visual C

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Core Concepts

• Objects
• Encapsulation
• Classes
• Inheritance
• Identity
• Domains

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Object

• Websters Dictionary definition of an object.
• Something that is or is capable of being seen,
  touched, or otherwise sensed.
• Add to this the concept that we want to store
  data and information about the behaviors of the
  object, and you have the information systems
  concept of objects

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Examples of Objects

• An employee, customer, vendor, and student are
  examples of person objects.
• A particular warehouse, regional office,
  building, and room are examples of place objects.
  
• A product, vehicle, equipment, video tape, or a
  window appearing on a users display monitor are
  examples of thing objects.
• An order, payment, invoice, application,
  registration, and reservation are examples of
  event objects.

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Object (Text definition, p.171)

• An entity that has a well-defined in the
  application domain, and has state, behavior and
  identity. Can be an
• Tangible or Visible Entity (e.g. Person, Place,
  or Thing)
• Concept or Event (e.g. Order, Registration)
• Artifact of the design process (e.g. User
  Interface, Scheduler)

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3 Sections of Object
Object Name
Attributes
Methods
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Customer Order
Object Name
ORDER
Order No. Order Date Promised Date CUSTOMER PRODUC
T Qty. Ordered
Attributes
Methods
Compute_Total
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Methods

• A processing routine that is encapsulated in an
  object and operates on the data described within
  that object

Order order number order data order status add
order modify order delete order display
status etc.
Customer
Display order status of order 23161
Message request
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Encapsulation

• Property that the attributes and methods of an
  object are hidden from outside world and do not
  have to be known to access its data values or
  invoke its methods.
• Interface--made known to outside world.
• Order received--methods to fulfill order not
  known to outside

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Classes

• Logical grouping of objects that have same
  attributes and behavior (methods)
• Pentel Color Pen BIC Stic have similar
  attributes they can both belong to WritingPen
  class.
• Faculty and students also have similar
  attributes, and could both belong to the PERSON
  class.

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Inheritance

• When classes are arranged in a hierarchy, each
  class assumes the attributes and methods of its
  ancestors (supertype).
• The class which inherits the attributes and
  methods is called a subtype

Person
Which attributes are unique to student
and faculty, and which are generic to person?
What about methods?
Student
Faculty
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Identity

• External identifier for each object that is not
  accessible to and cannot be modified by any other
  object or application
• Not a data value stored with the object
• Not a primary key as in other database models

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Domains

• May be of any data type
• standard domains from other data models
• integer, date, character
• abstract data type (defined by user)
• atomic (single) data value or multiple data
  values (array)
• another object or set of objects
• images, video, audio

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Limitations of ODBMS

• Lack of accepted standards (UML)
• Lack of development tools
• Performance
• Data Management Facilities
• concurrency control, backup recovery
• Query languages-
• advantage of encapsulation (ability to hide data
  structures within objects) causes problems with
  queries.

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Connecting Objects

• A connection is a mapping from one object class
  to another
• When a connection exists, expect objects to
  exchange messages

ORDER
CUSTOMER
PRODUCT
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Generalization

• Some things are types of other things
• Generalization hierarchy
• hierarchical grouping of objects that share
  common attributes and methods
• Employee--hourly, salaried, consultant
• Exhaustive--no other subclasses known
• Exclusive--must belong to one and only one
  subclass

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Assembly Structures

• Combining objects to form an assembly (whole)

ORDER
Order No. Order Date Promised Date CUSTOMER PRODUC
T Qty. Ordered
Objects
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Methods

• Encapsulation of methods (processing routines)
  within objects
• 3 Types
• Occur--provides basic maintenance
• Occur.Add Occur.Change
• Occur.Delete Occur.Select
• Calculate--math on data values
• Monitor--monitors some system or system
  characteristic e.g., InventoryCheck

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Advantages

• Closer representation of reality
• Greater productivity in developing applications
• Ability to model complex data types like images
  and documents