Class 2 | Week 1 | DAT601

Today Todd talked to us for about 40 minutes on conceptual modeling and also showed a brief intro video into the entity relationship model. He also briefly mentioned at the start of the class that there are a wealth of resources on the moodle to digest if one would be so inclined to get ahead on course content before it comes up in class.

After this conversation he sent us out in our groups to gather information from the queens garden park, nouns that we would then make into entities. This was all based on managing the park being our problem domain so all nouns gathered should be related to real things that the managers of the park would have responsibility over.

After each group put their gathered potential entities into a google sheet it was clear many people came up with many different ideas, showing how such a problem domain can be approached and divided into multiple categories(none of them being necessarily wrong, as long as it covers everything required).

Upon Todd then placing many of the gathered entities into some more abstract groups he then began to link these groups to the appropriate maintenance contractors that would be responsible for the various maintenance jobs the park requires. This has become complex rather quickly showing just show complex a E-R diagram can become just from 10-15 minutes of gathered data.




Random Personal Notes
Todd has resources on the moodle to watch/read in order to get ahead on upcoming course content


Conceptual modeling

Attributes are collected under entities/belong to entities

Shown as circles connected to the related entities

Someones address is a good example of attributed within entities, an address is made up of multiple attributes (number name, suburb, city etc etc)

Multi-valued attribute

    Example: extension numbers within an orgs phone number system

Derived attributes

    Example: Student has a date of birth, from this you can find out their age

Composite attribute

    Attribute made up of multiple attributes

Entity relationship model
  1. problem spec english
  2. design a conceptual solution (E-R Diagram)
Primary two things involved in this are entities and relationships.
What are entities?
entities are the IMPORTANT(noun within the problem domain that we need to capture multiple pieces of information from) nouns in your problem domain (to manage the park)
  e.g artist, album, song, genre?

Attributes related to ARTIST we are interested in capurting
    art.name
    birth.date
    age etc

Two or more entities within the problem domain share relationships one way or another

A binary relationship involves two entities

Passive voice vs active voice in relationships

    active: ARTIST records ALBUMS
    passive: ALBUMS records ARTIST

Constraints

    Cardinality
    Participation

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