1. Entity-Relationship Diagrams

2. Solutions to Homework #1

3. Project Partners, Inc. Data Flow Diagram

4. Project Partners, Inc. Data Flow Diagram

5. Project Partners, Inc. Data Flow Diagram

6. Project Partners, Inc. Process Details

7. Project Partners, Inc. Process Details

8. Project Partners, Inc. Process Details

9. Project Partners Information Requirements
Consider this list to be the minimum set of data.
Client information (Company name, address)
Project name and description.
This includes the starting and ending dates of the engagement; identifier of the underlying contract and an indication of the type of engagement (I.e., fixed price vs time & materials); and the client’s project manager information (their name, address, phone, and fax).
List of PPI’s standard project activities
Each of these activities includes its activity id, description, and an indicator of whether it is normally billable. Activities which are normally billable include analysis, design, programming, etc. Some activities (e.g., proposal preparation, vacation, sick time, etc.) are always considered to be overhead and hence are never billable.

10. Project Partners Information Requirements
List of PPI’s standard project activities
Note that it is PPI’s policy to “charge” anything to a project that can be attributable to a project or engagement, irrespective of whether it is billable and therefore to be included on an invoice. Please note that these are not specific instances of consultant’s activities, but a list of possible activities that could be entered by someone using the time sheet entry system.
Standard billing rate for each class of consultant
Other information related to the class of consultant should include a title and brief description.
Assignment information
Each consultant who can record billable time for a project should have information pertaining to the beginning and ending dates of their billable involvement along with their actual billing rate for the project. Non-billable time may be charged by the consultants or by other individuals to a given project. This insures that all time spent on a project is recorded even if it is never included in an invoice to the client.

11. Project Partners Information Requirements
Timesheet information
The information which appears on a consultant’s timesheet includes:
Client company identifier and name
project id and name; client’s project manager name, address, and phone number
type of work performed (generally drawn from a list of standard activities, such as analysis, design, programming, testing, implementation, etc.)
brief narrative description of the work performed
the amount of time, in hours and fractions, spent on each activity
an indication of whether the time should be billed to the client
Consultant information
Information about each consultant should include their id, name, consultant billing class, and phone number where they can be reached at the client site. Remember that a consultant may work at more than one client in any given period of time.

12. Entity-Relationship Diagrams

13. Entity-Relationship Diagram
A model that represents system data by entity and relationship sets.

14. ERD Elements Entities Relationships Identifiers Attributes
Things about which you collect information
Relationships
Means of association between entities
Identifiers
Unique attributes of entities
Attributes
Characteristic or property of the entity that is of interest

15. ERD Symbols Entities: rectangle
Relationships: diamond on a line with cardinality indicated (1 to M) or lines with “chicken feet”
Identifiers: underlined text
Attributes: text by the entity (if shown at all on diagram)

16. Sample ERDs Order Part Supplier Entity attributes: ORDER 1 CAN HAVE 1
ORDER: #, DATE, PART #, QUANTITY
PART: #, DESCRIPTION, UNIT PRICE, SUPPLIER #
SUPPLIER: #, NAME, ADDRESS
Order 1
CAN HAVE 1
Part
PART M
CAN HAVE 1
Supplier
SUPPLIER

17. Entity Sets
Each individual object is called an entity. A collection of such entities is an entity set.
Example: Joe, Jill, and Mary represent entities. They are all ascribed to the entity set, PERSON.
Example: A collection of projects is the project entity set.

18. Relationship Relationship Relationship set
One interaction between one or more entities
For example: if a person works on a project, there is a relationship between that person and the project
Relationship set
A collection of such relationships.
A component in an E-R diagram that represents a set of relationships with the same properties.

19. Notes on Entities and Relationships
We can actually see entities, but we cannot see relationships.
For example:
Entity sets: Person; project
Relationship: People work on projects. This becomes the relationship set “Work”
Persons
The set of people, set of projects and
set of working relationships.
Work
Projects

20. Entity-Relationship Structures
Persons are in departments
Persons work on projects
Persons
Parts
Supply
Suppliers
Projects use parts
Suppliers supply parts
Warehouses hold parts
Hold
Are-In
Work-On
Use
Warehouses
More complex relationship:
See persons and parts
Depts
Projects

21. Entities can have multiple relationships
Companies
Leases
Owns
Vehicles

22. More than two entity sets can be associated with the same relationship set
Relationship sets that include only two
entities are known as binary. More than
two are known as N-ary.
Customers
Buy
Stores
Each relationship in this set includes a person, a part bought
by the person, and the store where the purchase was made.
Parts
A person, a part bought by the person,
and the store where the purchase was made

23. It is always possible to remove an N-ary relationship by replacing it with an entity set.
Purchase Of By
From
Parts
Customer
Stores

24. Exercise
Employees are in departments
Each department has sections.

25. Departments
Have
Are in is not needed
Are in
Sections
Employ
Persons

26. Departments
Have
Are in is not needed
Sections
Employ
Persons

27. Identifiers
One of the attributes of an entity or relationship set is called the identifier
It has one important property: its values identify unique entities in the entity set.

28. Identifiers are underlined here
PERSON-ID
NAME
ADDRESS
PROJECT-ID
TIME-SPENT
START-DATE
BUDGET
Persons
Work
Projects
The set of people, set of projects and
set of working relationships.

29. Convention for Identifiers in Relationships
Use the identifiers of the entities that participate in the relationship as the relationship identifiers.
Identifiers are not file keys here. At this stage, they are the identifiers of entities that participate in the relationship.

30. Cardinality
The number of relationships in which one entity can appear.
An entity can appear in:
one (1) relationship;
any variable number (N) of relationships; and
a maximum number of relationships

31. Cardinality - Example Persons N Work M Projects
PERSON-ID
NAME
ADDRESS
PROJECT-ID
TIME-SPENT
START-DATE
BUDGET
Persons N
A persona can appear in more than one
WORK relationship, and so can a project.
If there was a limit to the number of times an
entity can take part in the relationship, then
N or M would be replaced by the actual
maximum number.
Work M
Projects
The set of people, set of projects and
set of working relationships.

32. Cardinality - Example Manager 1 Manage N Projects
MANAGER-ID
NAME
ADDRESS
PERSON-ID
PROJECT-ID
TIME-SPENT
START-DATE
BUDGET
Manager 1
Here a project has one (1) manager, whereas
a manager can manage any number (N) of
projects.
Manage N
Projects
The set of people, set of projects and
set of working relationships.

33. Cardinality - Example Manager 1 Manage N Projects
MANAGER-ID
NAME
ADDRESS
PERSON-ID
PROJECT-ID
TIME-SPENT
START-DATE
BUDGET
Manager 1
The denotes optional participation on the
project. If it is mandatory, then there is no
placed there.
Manage N
Projects
The set of people, set of projects and
set of working relationships.

34. Issues in building an ER-Diagram
How to choose entities, relationships and attributes
How to choose names
What steps should be followed

35. Choosing Atrributes
Attributes, just like entity and relationship sets, should express simple concepts.
E-R diagrams should not contain multivalued or structured attributes
For example:
PERSON-ID
DATE-OF-BIRTH
QULIFICATION* (asterisk means it is multivalued-repeating)
ADDRESS
(NUMBER, STREET, SUBURB)
PERSONS
Non-simple attributes
Addresses has structured attributes.
These should be replaced in the final diagram
by relationships.

36. Ex: Removing multivalued and structured attributes
PERSON-ID
DATE-OF-BIRTH
Persons
PERSON-ID
QUALIFICATION
HAVE
LIVE-AT
PERSON-ID
NUMBER
STREET
SUBURB
QUALIFICATION
NUMBER
STREET
SUBURB
QUALIFICATIONS
ADDRESSES

37. Choosing Object Set Names
Remember, that one goal of E-R modeling is to produce a model that is easily understood by users as well as computer personnel.
Entity sets are labeled as nouns
Relationship sets are labeled by verbs
Relationship sets are structured as prepositions when modeling structural relationships (see PURCHASES example [building has rooms])

38. Where to begin Start with entity sets
Look at how entities interact with each other and model this in terms of relationship sets
Then add cardinality to the system
Add attributes and choose identifiers

39. Dependent Entities
A dependent entity set depicts a set of entities whose existence depends on other entities.
INVOICE-NO
INVOICE-DATE
INVOICES
PROJECTS
PROJECT-ID
DATE-STARTED
INVOICE-
LINES
PROJECT-ID
TASK-NO
BUDGET
INVOICE-NO
LINE-NO
AMOUNT
TASKS
Note: dependent entities have composite identifiers

40. Machines Machines N Use N Use M M Projects PROJECTS Machine
Availability
Use N
Use M M
Projects
PROJECTS

41. SUBSETS Example: generic: loan applications
Different types of loan applications which have unique attributes

42. PERSONS STUDENTS TEACHERS N N TAKES TEACHES M M COURSES
Occurrence diagram for entity set PERSONS
and its subsets
PERSON-ID
NAME
ADDRESS
PERSONS
PERSON-ID
MAJOR
STUDENTS
TEACHERS
PERSON-ID
DATE-HIRED N N
PERSON-ID
COURSE-NO
SEMESTER-TAKEN
RESULT
PERSON-ID
COURSE-NO
SEMESTER-TAUGHT
TAKES
TEACHES M M
COURSES
COURSE-NO
COURSE-NAME

43. STAFF STUDENTS CLUB-MEMBERS N USE M COURTS STUDENT-ID STAFF-ID MAJOR
MEMBER-NO
STAFF
STAFF-ID
DATE-JOINED
MEMBER-NO.
STUDENTS
CLUB-MEMBERS
MEMBER-NO.
MEMBER-GRADE
DATE-JOINED-CLUB
COMBINING SUBSETS
FROM A NUMBER
OF ENTITIES N
USE
MEMBER-NO
COURT-NO
NO-TIMES-USED M
COURTS
COURT-NO
LOCATION