Conceptual Design Lecture 4

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Conceptual DesignLecture 4

• Database Technology Level I

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Aims

• To introduce Business Rules
• To identify what a Business Rule is
• To Introduce Business Operations
• To identify what a Business Operation is.

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Conceptual Design Requirements

• E-R Diagram
• Diagram Script
• Business Rules
• Operations

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Business Rules

• What is a Business Rule?
• A business rule
• is used to describe properties of an application
  which cannot be expressed with a conceptual
  model.
• defines or constrains an aspect of the use of the
  database.
• often focuses on access rights or business
  calculations.

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Business Rules

• A Business Rule can be
• integrity constraint
• A derivation

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Structure of Business Rules

• Integrity Constraints can always be expressed in
  the form of assertions.
• An appropriate structure is
• ltconceptgtmust/must notltexpression on conceptsgt

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Integrity Constraints

• Head of subject must belong to the subject
• A lecturer must not have a salary greater than
  that of their head of subject

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Structure of Business Rules

• Derivations can be expressed by specifying the
  operations that allow us to obtain the derived
  concept.
• An appropriate structure is
• ltconceptgtis obtained byltoperations on conceptsgt

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Derivation

• The number of students on a module is obtained by
  counting the students registered on that module.
• The total cost of a product on an order is
  obtained by multiplying the product cost by the
  quantity ordered

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Business Rules

• Business rules can be listed as follows

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Operations on the data

• An operation is a task carried out on the data,
  including
• Add (Insert)
• Edit (Update)
• Browse (Select, View)
• Delete
• Effectively, the life cycle of an entity.

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Fragment of Staff Interview regarding student
applications

• When I get my copies, I check past records to see
  if the student is a previous student. If there is
  a past record, I check that it is up-to-date and
  if the record is not up-to-date, I update it. If
  the student is a new student, a student record
  card is created. The date of the most recent
  application by a student is also recorded.

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Fragment of Staff Interview regarding student
applications

• When I get my copies, I check past records to see
  if the student is a previous student. If there is
  a past record, I check that it is up-to-date and
  if the record is not up-to-date, I update it. If
  the student is a new student, a student record
  card is created. The date of the most recent
  application by a student is also recorded.

Browse student record
Edit student record
Add new student record
Update student record
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Operations on the data

• The operations identified from the staff
  interview fragment are

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Logical Design

• Read Chapter 4 Logical Design
• Chapter 4 is not required for next weeks in-class
  test.

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In-class Test for next week

• Test is in 2 sections
• Section A Multiple-choice
• Section B Conceptual Model

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Section A
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Section A ANSWERS
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Section B

• You will be given a description of a system.
• From that you will be required to complete the
  E-R Diagram, The Diagram Script and you will need
  to identify any business rules and operations
  from that description.
• See Business rules and operations on page 67 of
  Part booklet

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Section B Part I

• Here is an extract from a description of a
  system.
• Hope Town Rentals has several branches, each of
  which manages holiday accommodation situated in
  the geographical area for which the branch is
  responsible. There are two kinds of holiday
  accommodation villas and apartments. The
  company takes bookings from customers for holiday
  accommodation. Each customer can make several
  bookings but a booking is only made by one
  customer. Each booking may be for several villas
  and/or apartments and there can be many bookings
  for each villa or apartment. Every customer is
  assigned an account with the company, which holds
  financial details relating to that customer (for
  example, the total amount of money owed by the
  customer to the company.

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Section B Part I

• Here is an extract from a description of a
  system.
• Hope Town Rentals has several branches, each of
  which manages holiday accommodation situated in
  the geographical area for which the branch is
  responsible. There are two kinds of holiday
  accommodation villas and apartments. The
  company takes bookings from customers for holiday
  accommodation. Each customer can make several
  bookings but a booking is only made by one
  customer. Each booking may be for several villas
  and/or apartments and there can be many bookings
  for each villa or apartment. Every customer is
  assigned an account with the company, which holds
  financial details relating to that customer (for
  example, the total amount of money owed by the
  customer to the company.

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Section B Fill the diagram
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Section B
Diagram Script
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Section B

• Revision of
• E-R diagram
• Diagram Script
• Identification of business rules
• Identification of operations

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Section B part II

• Further system description
• The Villas are situated either on a villa
  complex with shared leisure facilities or they
  are private self contained villas with private
  facilities. For each villa complex we record,
  Complex Name, Manager Name and no of swimming
  pools on the complex. For each private villa we
  record Garden yes/no, BBQ yes/no and swimming
  pool yes/no. Adjust the diagram and diagram
  script to reflect this requirement

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Section B part II

• Further system description
• The Villas are situated either on a villa
  complex with shared leisure facilities or they
  are private self contained villas with private
  facilities. For each villa complex we record,
  Complex Name, Manager Name and no of swimming
  pools on the complex. For each private villa we
  record Garden yes/no, BBQ yes/no and swimming
  pool yes/no.

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Marking

• You will get marks if the answer is correct.
• You may lose marks if what you have modelled is
  fundamentally incorrect.
• Your marks will be moderated by another marker
  before finally entering into the Portal system
• You will be given feedback quickly according to
  university rules

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Revision

• For the test you should revise Chapter 3 of your
  Database Technology Part I booklet.
• Nothing from Chapter 4 will be assessed.