Conceptual Modeling
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What is a Conceptual Model?
• A mental model of the world around us
• Models necessarily mean simplification/abstraction
Possible Conceptual Models of “Attraction”
F = GMm/R2
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Exercise: Imagine a Conceptual Model
• Working in groups of three or four come up with various
conceptual models for one of the following (make sure
everyone contributes):
Hallowe’en
Christmas
Buying a Cow
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First Day at School
Things we see in your examples:
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Models often reflect modeler’s point of view
Some models are quite specific – single detail
Some models are quite general/abstract
Modeling language can differ – natural, picture, song
Hard if you are not familiar with the situation
Not everyone in the group contributes the same
Did someone lead the discussion?
– Organizer vs Idea person
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Hotel Example:
Model a Hotel and its Operations.
• Divide yourselves in groups again
• Each group pick on of the following areas:
– Reception (mine)
– Kitchen
– Room Service
– Reservations
– Concierge
– Restaurant
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Reception:
• List Things of Interest:
– Guest, Room, Arrival/Departure Times, Messages,
Payment Method, Bill
• Spread out the things and draw boxes around them
• Draw Lines between related things
Time: A/D
Room
Guest
Message
Bill
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Payment
Observations:
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New, graphical language
Lots of detail hidden or missing (how many messages?)
Diagrams overlap in some places
Each diagram shows only part of the big picture
Synonyms? Homonyms?
Not all information is modeled
What happens if one department “owns” its own data?
– Is it always possible?
• Leader? Negotiation? Different points of view ok?
• Our diagrams show areas of responsibility, a business
model even!!
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Summary:
• Our individual views are called external views.
• If we were to combine them in a single picture,
negotiating synonyms and homonyms, we would have a
conceptual model of a hotel business.
• This conceptual model would be a first step towards a
design for a database for a hotel but it is a picture of
reality, not a database.
• Graphical languages let us see everything at once
instead of sequentially as text does.
• Our language needs to be more expessive
• People can be productive in teams if they have a
common goal and good tools.
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Formal Definitions:
• A conceptual schema/model is a map of concepts and
their relationships.
• An external schema/view represents one person’s view
of the world around her.
• In the context of database, a conceptual model is the
merging of various related external views.
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Homework (on the web):
• Read the poem “The Blind Men and the Elephant” and ...
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The Blind Men and the Elephant
Six wise men from India,
An elephant did find.
They set about to feel its parts,
(For all of them were blind.)
The fourth had come upon the trunk
Which he did seize and shake,
Quoth he, "This so-called elephant
Is really just a snake."
The first he felt towards the tusk,
"It does to me appear,
This marvel of an elephant
Is very like a spear."
The fifth had felt the creature's ear
And fingers o're it ran,
"I have the answer, never fear,
The creature's like a fan."
The second sensed the creature's side
Extended flat and tall,
"Ahah!", he cried and did conclude,
"This animal's a wall."
The sixth had come upon the tail
As blindly he did grope,
"Let my conviction now prevail,
This creature's like a rope."
The third had reached towards a leg
And said, "It's clear to me,
What we should all have said instead.
This Creature's like tree."
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And so these men of missing sight
Each argued loud and long,
Though each was partly in the right
They all were in the wrong.
Homework (continued):
• Prepare a conceptual model of an elephant, using as
your starting point, the external views expressed by each
of the men in the poem.
• Find out what you can about the poem and its author.
• Explain how the poem relates to the task of creating a
conceptual model of an organization’s information.
• The poem does not introduce a “seeing” man who can
set the blind men straight. Who plays the role of the
seeing man in the organizational context?
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Homework (continued):
• One student once gave me the following answer:
A fan, a spear, a wall, a rope,
A snake up in a tree,
Disparate views,
We can not hope,
Will represent reality.
Why is his skepticism unlikely to be a problem in in creating
a conceptual model of an organization’s information.
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