Conceptual Models

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Conceptual Models
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Overview

• To frame our discussion consider
• Identify the characteristics of a conceptual
  model.
• Investigate the construction of a conceptual
  model.
• Define strategies for constructing a conceptual
  model.

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Outline

• Foundations
• Strategies
• Model Construction

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Definition

• A conceptual model is a representation of
  concepts in the problem domain.
• The essence of OO analysis is elaborating a set
  of objects/concepts.

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Representation in UML

• A conceptual model is illustrated by a set of
  static structure diagrams. This diagram contains
  candidate object identified from the problem
  domain.

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Model Content

• Concepts
• Associations between concepts
• Attributes of concepts

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Example
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Concepts (1)

• We use the broader term concept to discuss
  exploring the problem domain. Concept subsumes
  the notion of object but includes a broader
  category - idea, thing. We tend to think of
  objects as concrete and physical whereas concepts
  dont require that specification.

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Concepts (2)

• Symbol
• representation for a concept
• Intension
• Defiinition of a concept
• Extension
• examples representing the concept

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Strategies

• Concept Category List
• Noun Phrase Identification

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Concept Category List

• The author provides a list of categories. Think
  through you problem statement and determine items
  from the problem that may fit a particular
  category.

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List
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Caveat

• There is a danger in being caught up in worrying
  over whether something fits in a particular
  category.
• It is better to overspecify a conceptual model
  with lots of fine-grained concepts, than to
  underspecify it.

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Noun Phrases

• Identify the nouns and noun phrases found in
  textual descriptions of the problem domain.
• Requirements
• Use cases

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Example
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Making a Conceptual Model

• 1. List the candidate concepts.
• 2. Draw a conceptual model.
• 3. Add the associations necessary to record
  relationships.
• 4. Add the necessary attributes.

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Candidate Concepts

• Generate the list of concepts from the category
  list and noun phrase identification.

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Rule of Thumb

• A conceptual model is not absolutely correct or
  incorrect, but more or less useful. It is a tool
  for communication.

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Specification Concepts

• Add specification or description concepts when
• Deleting instances of things they describe
  results in a loss of information.
• It reduces redundant or duplicated information.

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Association Guidelines

• Focus on those associations for which knowledge
  of the relationship needs to be preserved.
• Concepts are more important that associations.
• Too many associations can be confusing.
• Avoid redundancy or derivable associations.

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From POS