IS 257 - Fall 2002 2002.08.29 - SLIDE 1
Database Design: Conceptual Model and ER Diagramming
University of California, Berkeley
School of Information Management and Systems
SIMS 202: Information Organization and Retrieval
IS 257 - Fall 2002 2002.08.29 - SLIDE 2
Lecture Outline
• Review– Information Systems Planning– Information Systems Architecture– Information Engineering
• Database Design
• ER Diagrams
• Developing the Conceptual Model
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Lecture Outline
• Review– Information Systems Planning– Information Systems Architecture– Information Engineering
• Database Design
• ER Diagrams
• Developing the Conceptual Model
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Review
• Information Systems Planning
• Information Systems Architecture
• Information Engineering
• Database Design
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Information Systems Architecture
• Zachman ISA Framework components– Data
• The “what” of the information system– Process
• The “how” of the information system– Network
• The “where” of the information system– People
• Who performs processes and are the source and receiver of data and information.
– Events and Points in time• When processes are performed
– Reasons• For events and rules that govern processing
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Information Engineering
• A formal methodology that is used to create and maintain information systems
• Starts with the Business Model and works in a Top-Down fashion to build supporting data models and process models for that business model
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Information Engineering
Planning
Design
Analysis
Implementation
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Lecture Outline
• Review– Information Systems Planning– Information Systems Architecture– Information Engineering
• Database Design
• ER Diagrams
• Developing the Conceptual Model
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Database Design Process
ConceptualModel
LogicalModel
External Model
Conceptual requirements
Conceptual requirements
Conceptual requirements
Conceptual requirements
Application 1
Application 1
Application 2 Application 3 Application 4
Application 2
Application 3
Application 4
External Model
External Model
External Model
Internal Model
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Stages in Database Design
• Requirements formulation and analysis
• Conceptual Design -- Conceptual Model
• Implementation Design -- Logical Model
• Physical Design --Physical Model
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Database Design Process
• Requirements formulation and analysis– Purpose: Identify and describe the data that
are used by the organization– Results: Metadata identified, Data Dictionary,
Conceptual Model-- ER diagram
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Database Design Process
• Requirements Formulation and analysis– Systems Analysis Process
• Examine all of the information sources used in existing applications
• Identify the characteristics of each data element– numeric– text– date/time– etc.
• Examine the tasks carried out using the information
• Examine results or reports created using the information
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Database Design Process
• Conceptual Model– Merge the collective needs of all applications– Determine what Entities are being used
• Some object about which information is to maintained
– What are the Attributes of those entities?• Properties or characteristics of the entity• What attributes uniquely identify the entity
– What are the Relationships between entities• How the entities interact with each other?
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Database Design Process
• Logical Model– How is each entity and relationship
represented in the Data Model of the DBMS• Hierarchic?• Network?• Relational?• Object-Oriented?
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Database Design Process
• Physical (AKA Internal) Model– Choices of index file structure– Choices of data storage formats– Choices of disk layout
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Database Design Process
• External Model– User views of the integrated database – Making the old (or updated) applications work
with the new database design
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Lecture Outline
• Review– Information Systems Planning– Information Systems Architecture– Information Engineering
• Database Design
• ER Diagrams
• Developing the Conceptual Model
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Entity
• An Entity is an object in the real world (or even imaginary worlds) about which we want or need to maintain information– Persons (e.g.: customers in a business,
employees, authors)– Things (e.g.: purchase orders, meetings,
parts, companies)
Employee
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Attributes
• Attributes are the significant properties or characteristics of an entity that help identify it and provide the information needed to interact with it or use it. (This is the Metadata for the entities.)
Employee
Last
Middle
First
Name SSN
Age
Birthdate
Projects
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Relationships
• Relationships are the associations between entities. They can involve one or more entities and belong to particular relationship types
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Relationships
ClassAttendsStudent
PartSuppliesproject parts
Supplier
Project
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Types of Relationships
• Concerned only with cardinality of relationship
TruckAssignedEmployee
ProjectAssignedEmployee
ProjectAssignedEmployee
1 1
n
n
1
m
Chen ER notation
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Other Notations
TruckAssignedEmployee
ProjectAssignedEmployee
ProjectAssignedEmployee
“Crow’s Foot”
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Other Notations
TruckAssignedEmployee
ProjectAssignedEmployee
ProjectAssignedEmployee
IDEFIX Notation
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More Complex Relationships
ProjectEvaluationEmployee
Manager
1/n/n
1/1/1
n/n/1
ProjectAssignedEmployee 4(2-10) 1
SSN ProjectDate
ManagesEmployee
Manages
Is Managed By
1
n
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Weak Entities
• Owe existence entirely to another entity
Order-lineContainsOrder
Invoice #
Part#
Rep#
QuantityInvoice#
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Supertype and Subtype Entities
ClerkIs one ofSales-rep
Invoice
Other
Employee
Sold
Manages
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Many to Many Relationships
Employee
ProjectIsAssigned
ProjectAssignment
Assigned
SSN
Proj#
SSN
Proj#Hours
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Lecture Outline
• Review– Information Systems Planning– Information Systems Architecture– Information Engineering
• Database Design
• ER Diagrams
• Developing the Conceptual Model
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Developing a Conceptual Model
• Overall view of the database that integrates all the needed information discovered during the requirements analysis.
• Elements of the Conceptual Model are represented by diagrams, Entity-Relationship or ER Diagrams, that show the meanings and relationships of those elements independent of any particular database systems or implementation details.
• Can also be represented using other modeling tools (such as UML)
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Developing a Conceptual Model
• Building the Conceptual Model for the Diveshop database
• Names for the Diveshop company?
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Developing a Conceptual Model
• We will look at a small business -- a diveshop that offers diving adventure vacations
• Assume that we have done interviews with the business and found out the following information about the forms used and types of information kept in files and used for business operations...
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Primary Business Operations
• The shop takes orders from customers for dive vacations.
• It ships information about the dive vacation to the customers.
• It rents diving equipment for the divers going on the trips (these may include additional people other than the customer)
• It bills the customer for the vacation and for equipment rental or sales.
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Business Operations (cont.)
• It arranges sub-trips to particular dive sites at the primary location.
• It provides information about the features of various sites to help customers choose their destinations.– Features include sea life found at the location
and shipwrecks
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Business Operations (cont.)
• Each dive order (or sale or trip) is on an invoice to one customer.– Invoices contain:
• Line items for each type of equipment ordered,• Total amount due for the invoice,• Customer information:
– Name, address, phone, credit card info.
• Information must be kept on inventory of dive equipment.
• There are multiple types of dive equipment:– The prices charged for sale or rental are
maintained.
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Business Operations (cont.)
• Destination information includes:– Name of the destination– information about the location (accomodations,
night life, travel cost, average temperatures for different times of the year
• Destinations have associated dive sites.• Dive Sites have associated features
– Sea life – Shipwrecks
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Business Operations (cont.)
• One record is kept for each order by a customer and will include the method of payment, total price, and location information. (I.e. Customers may have multiple orders)
• The company needs to know how an order is to be shipped.
• The shop has to keep track of what equipment is on-hand and when replacements or additional equipment is needed
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Entities
• Customer
• Dive Order
• Line item
• Shipping information
• Dive Equipment/ Stock/Inventory
• Dive Locations
• Dive Sites
• Sea Life
• Shipwrecks
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Diveshop Entities: DIVECUST
Name
Customer no
Street
State/ProvCityZIP/Postal
Code
Country
First Contact
PhoneDiveCust
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Diveshop Entities: DIVEORDS
CustomerNo
Order no
SaleDate
ShipVia
DestinationCCExpDate
CCNumber
PaymentMethodDiveOrds
No ofPeople
VacationCost
ReturnDate
DepartDate
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Diveshop Entities: DIVEITEM
Item no
Order no
Rental/Sale
Qty
Line Note
DiveItem
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Diveshop Entities: SHIPVIA
Ship Via
ShipCost
ShipVia
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Diveshop Entities: DiveStok
Description
Item No
EquipmentClass
ReorderPoint
On Hand Cost
SalePrice
DiveStokRentalPrice
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Diveshop Entities: DEST
Destinationname
Destination no
Avg Temp (F)
SpringTemp (F) Avg
Temp (C)Summer
Temp (C)
SummerTemp (F)
TravelCost
WinterTemp (C)
FallTemp (F)
FallTemp (C)Dest
WinterTemp (F)
Accommodations
Body ofWater
NightLife
SpringTemp (C)
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Diveshop Entities: SITES
Destinationno
Site no
Site Name
SiteNotes
SiteHighlight
DistanceFrom Town (M)
DistanceFrom Town (Km)
Skill Level
Visibility(ft)
Depth (m)
Depth (ft)Sites
Visibility (m)
Current
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Diveshop Entities: BIOSITE
SpeciesNo
SiteNo
BioSite
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Diveshop Entities: BIOLIFE
Category
Species no
CommonName
Length(cm)
SpeciesName
Length(in)
Notesexternal
GraphicexternalBioLife
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Diveshop Entities: SHIPWRCK
Site no
Ship Name
Category
InterestType Tonnage
Length (ft)
Beam(m)
Beam(ft)
Length(m)Shipwrck
Cause
Commentsexternal
DateSunk
Passengers/Crew
Graphicexternal
Survivors
Condition
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Functional areas
• Ordering
• Inventory
• Supplies
• Shipping
• Billing
• Location/Site Selection– We will concentrate on Ordering and
Location/Site Selection (these are joined tasks)
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Ordering
Orders(DIVORDS)
Customer(DIVECUST)
Customers place OrdersEach Order needs Customer information
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Ordering
DiveOrdsOrdersDiveCust
Customer No ship
ShipVia
Order No
Ship Via
DiveItem Repeatingattribute
Customer No
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Ordering Normalization
DiveCust Orders
Customer No
DiveOrds
Ship
ShipVia
Order No
Ship Via
DiveItemContains
Item No
QtyOrder No
Customer No
Rental/sale
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Details of DiveItem
DiveStokSuppliesSupplier
Company# Has
DiveItem
Item No
Item No
On Hand
Sale Price
Order No
m n
We’re ignoring this part...
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Ordering: Full ER
CustomerNo
ShipVia
DestShipVia
DiveStok
DiveItem
DiveOrds
DiveCust
CustomerNo
ShipVia
OrderNo
OrderNo
ItemNo
ItemNo
DestinationName
Destination
Destinationno 1
1
1
1
1n
n
n
n
n
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Location/Site Selection
DestGoing
to?DiveOrds
DestinationNo
DestinationName
Destination
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Destination/ Sites
Dest
Sites
DiveOrds
CustomerNo
OrderNo
DestinationName
DestinationSite No
Destinationno
Destinationno
1
1
n
n
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Sites and Sea Life 1
BioLife
Sites
Site NoDestination
no
Multiple occurrencesof sea life...
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Diveshop ER diagram: BioSite
SpeciesNo
SiteNo
BioSite
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Sites and Sea Life 2
Sites
BioSite
BioLifeSpeciesNo
Site No
Site No
Destinationno
SpeciesNo
1
1
n
n
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Sites and Shipwrecks
Sites
ShipWrck
Site NoDestination
no
Site No
1/n
1
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DiveShop ER DiagramCustomer
No
ShipVia
Dest
Sites
BioSite
ShipVia
ShipWrck
BioLife DiveStok
DiveItem
DiveOrds
DiveCust
CustomerNo
ShipVia
OrderNo
OrderNo
ItemNo
ItemNo
DestinationName
Destination
SpeciesNo
Site No
Destinationno
Site No
Destinationno
SpeciesNo
Site No
1
1
1
1
1
1
1/n
1
1n
n
n
n
n
n
n
n
1
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What must be calculated?
• Total price for equipment rental?
• Total price for equipment sale?
• Total price of an order?– Vacation price– Equipment (rental or sale)– Shipping
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What is Missing??
• Not really an “enterprise-wide” database– No personnel
• Sales people• Dive masters• Boat captains and crew• payroll
– Local arrangements• Dive Boats• Hotels
– Suppliers/Wholesalers for dive equipment• Orders for new/replacement equipment
– No history (only current or last order)
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Next Time
• TUESDAY: – More on UML database modeling– Designing the Logical Model