| Which levels of Data modeling are there? | Conceptual
Logical
Physical
Implementation |
| What is meant by "Modeling the world"? | We want to create a virtual world (IT-system) that is one-to-one with the (future) physical world.
• The physical world has a structure
• An event in the real world might have an effect on our virtual world
We want to model the “world” that is in scope:
• Model the Entities we want to manage
• Model the data (Attributes) we need for our purpose
• Model the Relationships between the Entities is scope |
| Why do we want to do data modeling? | Organizations need to understand the structure and flow of data Data models facilitate clarification of …
• the data the systems need to store and manage
• the most efficient way of organizing the data
• potential risks and challenges related to data within the organization
Think about how many systems of our everyday-life that depends on data: banking, traffic, social networks… |
| In relation to Entity relation diagrams - how do we use Entities and attributes? | • Something that has identity and properties
• Lecturer, Car, Location, Chair, Organizational unit, |
| What is atomic attributes? | All attributes within an entity should be atomic, meaning we split them out into different sections. f.x with a name being split into:
First_name: Christian
Middel_name: Møller
Last_name: Rasmussen |
| Which attributes should be assigned to an entity? | Entities have attributes, which are characteristics that are important to the system e.g. a customers name, phone number, product name, price etc. a record is a specific instance of an entity. |
| What are entity ID's? | • Every entity must have an identity i.e. in ERD a primary key
• The primary key is an attribute or combination of attributes that uniquely identify an instance of the entity
• In other words, no two instances of an entity may have the same value for the primary key (think MID) |
| What are entity relations? | Entities can be in a relationships with each other: Entity Relationships
Diagram
› E.g. A Customer places an Order or a Student attend a School
› Relationships are modeled by straight lines between entities |
| Which cardinalities can we use? | E.x:
One ADVISOR can be related to many STUDENTS
One STUDENT can be related to only one ADVISOR
It is a 1:n relationship
Important:
• Business logic/rules drives the model
• It is NOT the model that defines the business logic/rules |
| What is Dark Data? | Data that is not used to derive decision-making. This account for around 80% of the total data in the society.
Dark data ia about linkage something that ties all the data together to reveal what’s truly going on with the brand. |
| What is included in the process of shaping a model? | 1. Identify entities and attributed
2. Chose a Primary Key(quantity
3. Models relationships
4. Decide on business rules
5. Check the model. |
