Hierarchical ER Diagrams (HERD) The Method and Experimental Evaluation
Revital Danoch, Peretz Shoval* and Mira Balaban
Department of Information Systems Engineering
Ben-Gurion University of the Negev P.O.Box 683, Beer-Sheva 84105, Israel
{danochav,shoval}@bgumail.bgu.ac.il; [email protected]
The paper was presented at:
International Workshop on Conceptual Modeling Quality (IWCMQ’02), October 11, 2002, Tampere, Finland
This file contains only the figures and abstract of the paper
Abstract
HERD (Hierarchical Entity-Relationship Diagram) is a semi-algorithmic, bottom-up method for creating hierarchical ER diagrams
(ERD) from a given “flat” diagram. The method is based on three packaging operations, which group entity and relationship types
according to certain criteria. The packaging operations are applied in several steps on a given (presumably large) ERD. The result is
a hierarchy of simple and interrelated diagrams - ER structures - with external relationships to other structures. At the top of the
hierarchy is the HERD-Tree diagram, which provides the most general view of the database schema. We conduct an experimental
comparison of HERD and flat ERD from the point of view of user comprehension; time to complete comprehension tasks, and user
preference of models. Results of the comparison reveal that there is no significant difference in comprehension of the two types of
ER diagrams, and in the time it takes to complete the comprehension tasks, but that users prefer HERD diagrams.
equipment
name
equipment
code
equipment
price
Medical
Equipment
supply
date
Surgery
code
Pharmacy
Surgery
(1,n)
Storage
diagnosis
date
(0,n)
Surgeon
patient ID
Patient
Examination
Recipe
Patient
Hospitalization
(1,1)
(1,1)
(1,1)
(0,n)
Hospitalized
in
(0,n)
ation
patient
address
Employee
examination
result
Have been done
Sensitivity
examination
code
examination
description
nurse
degree
day of
placement
research
code
Placement
(0,n)
Research
Proposal
no. of
years
from hour
(0,n)
to hour
diagnosis
hour
diagnosis
date
research
name
sensitivity
symptom
(1,1)
Examination
Researcher
Diagnosis
diagnosis
descriptio
n
Phys.
Placement
(0,n)
(0,n)
sensitivity
code
Nurse
(1,n)
Physician
Diagnosis
Hospitalization
diagnosis
Sensitive
(0,n)
(1,1)
Physician in
charge
(1,1)
Employment
Guard
(1,n)
(0,n)
(1,1)
employee
ID
Physician
(1,n)
(0,n)
hospitalization
date
Guarding
Agency
employee
role
physician
number
(1,1)
(0,n) Hospitaliz
Actual
Examination
(0,n)
employee
name
Works for
dosage
patient
name
(0,n)
examination
hour
Manager
Patient
examination
date
supplier
address
Supplier
Specialization
physician
examination
agency
name
employee
address
Department
Physician
(1,n)
supplier
name
(1,n)
no of beds
(0,n)
medicine
name
Patient
operation
(1,n)
supply
quantity
Supply
(1,n) (0,1)
Medicine
Actual
Surgery
(0,n)
Organizational
unit
(1,n)
Surgeries
(0,n)
no of
employees
(1,n)
diagnosis
hour
(1,1)
Surgery
description
dept.
name
(1,n)
sensitivity
description
fund
name
(1,1)
Fund
fund
address
Figure 1: Flat ER Diagram of Hospital Schema
Submitted
to
agency
owner
agency
address
1.2 Organizational Units and Supply
equipment
code
equipment
name
Storage
equipment
price
Medical
Equipment
(1,n)
Medicine
(3.1)
(1,n)
supply
date
Pharmacy
dept.
name
(1,n)
no of
employees
supply
quantity
Supply
(1,n)
Manager
(1,1)
Employee
(1.6)
(0,n)
Works for
(0,1)
(1,n)
Hospitalized
in
Supplier
(1,n)
no of beds
(1,1)
Hospitaliz
ation (1.1)
supplier
name
(1,n)
Organizational
unit
Department
Figure 2: Structure produced by Step 1 due to operations b and c
(0,n)
physician
examination
Actual (1.1)
Examination
Employee
(1.6)
1.4 Physicians Placement
physician
number
Actual
Surgery
(1.1)
(0,n)
Diagnosis
(1.1)
Specialization
(0,n)
Physician
Diagnosis
(1,n)
Surgeon
(1,n)
(1,n)
Physician
(1,n)
Researcher
from hour
Hospitaliz
ation (1.1)
Physician in
charge
(0,n)
(1,1)
day of
placement
Phys.
Placement
to hour
(0,n)
Placement
(0,n)
Figure 3: Structure produced by Step 1 due to operation a
Research
Proposal
(1.3)
2.1-Staff and Research
Physicians
placement
(1.4)
Research
Funds (1.3)
financing
Figure 4: Structure produced by Step 2 due to operation b
2.2-Staff and Guarding
Hospital
Employees
Guarding
(1.5)
(1.6)
Figure 5: Structure produced by Step 2 due to operation b
3.1 Hospital
Staff and
Research (2.1)
Hospitality
Patient
Hospitalization
(1.1)
Medicine
Recipes
medicine
name
Hosp.
department
Storage
Staff and
Guarding (2.2)
Employment
Organizational
units and supply
(1.2)
Figure 6: Top-level structure
1.6 Hospital Employees
employee
address
employee
name
Manager
(0,1)
employee
ID
employee
role
(1,1)
Organizational
unit (1.2)
Works for
(0,n)
Employee
(1,n)
nurse
degree
Guard
(0,n)
Nurse
Employment
Physician
agency
name
(1.4)
agency
owner
(1,1)
agency
address
Guarding
Agency
Figure 7: Revised structure 2.1 produced in Step 3 due to the combination of
Structures 1.6 and 1.5
Hospital – 3.1
Medicine
Staff and
Research – 2.1
Nurse
Figure 8: HERD-Tree (before changes applied in Step 3)
Hospital
Employees –
16
Employee
Guarding agency
Guard
Guarding –
1.5
Placement
Physicians
Placement –
14
Fund
Department
Organizational unit
Pharmacy
Supplier
Medical equipment
Actual surgery
Examination
Actual examination
Diagnosis
Hospitalization
Sensitivity
Patient
Research
Funds – 1.3
Physician
Organizational
Units and Supply –
1.2
Research proposal
Patient
Hospitalization –
1.1
Staff and
Guarding– 2.2