The following notes were taken during a lecture in COMP 230 Systems Analysis & Design at Camosun College by Marla Weston.  These notes are here mainly to help me study, but if you can find some guidance through them then all the better!

Conceptual Data Modeling Process

In the design stage, the conceptual data model is translated into a physical design

Deliverables and Outcome

• Primary deliverable is an entity-relationship diagram (ER Diagram)
• Second deliverable is a set of entries about data obnects to be stored in repository or project dictionary
  • repository links data, process, and lopgic models of an information system
  • data elements included in the DFD must appear in the ERD

Conceptual Data Model

• The 30,000 foot view.
• Very high level
• Just the system and any external entities that interact with it.

Gathering Information for Conceptual Data Modeling

• Top Down approach for the data model is derived from an intimate understanding of the system
• Bottom Up approach which builds simple low-level objects into more complex higher-level objects.

Entity Relationship Model

• Entity type name should always be a singular noun
• Entity type definition should:
  • Include a statement of what the unique characteristics is/are for each instance
  • Make clear what entity instances are included and not included in the entity type
• Attributes: a named property characteristic of an entity that is of interest to the organization
  • Naming an attribute: eg Vehicle_ID
  • Place its name inside the rectangle for the associated entity in the E-R Diagram
  • Name is a noun and should be unique
  • States what the attribute is and possibly why it is important
  • Should indicate if a value is required or optional
• Relationships
  • A relationship name is a verb phrase and avoid vague names
  • A relationship definition should:
    • Explain any optiontion participation
    • Explain the extent of history that is kept in the relationship
• Associative Entity
  • An entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances
  • Used mostly in many-many relationships
• Subtypes: A type together with a constraint which possibly restricts the allowed range of values
• Supertypes: A generic entity type that has a relationship with one or more subtypes
• Business Rules: specifications that preserve the integrity of the logical data model
  • Entity Integrity
  • Referential
  • Trigger/Triggering Operation – An assertion or rule that governs the validity of data manipulations such as insert update and delete