Dat601

What have I learnt?

Before any creations of tables and writing sql scripts take place designing an overall “map” off all identified Entity types and their associated attributes

The class was placed in groups for he design of process and due to me having a chest infection and fever I was not present for the design of the conceptual model pictured below.

Something new that i learnt from the course material provided is that Attributes can either be simple or composite in nature. Simple attributes also known as Atomic attributes cannot be broken down any further. An example of a simple Attribute will be a student Id number.

As for the composite attributes this can be further broken down into sub groups. A good example for a composite attribute would be an address. which could be further divided into house number, street name and suburb.

Overall so far I have found the Dat601 class interesting and well presented. I look forward to taking the concept model and creating a Logical model where we start to identify primary and foreign keys that our tables will need to link with one another.

Dat601 Assessment 1 Blog)

For the first assessment we had to design a conceptual model for the for a fictional company that distributes drones across the globe that not only collects data such as ambient_light_strength, Humidity, Temperature, each BtBox also comes equipped with Video cameras that can stream the locations they are placed in throughout the world. The company offers a wide range of subscriptions that range from simple viewing of streams to exclusive ownership of the data that is collected from a BT_Box.

Trying to get a good understanding of how the company would work if it were real was the hardest part of of the assessment and no two people had the same Conceptual model as each person understood the brief slightly different.

Once the assessment brief was understood to a satisfactory level a conceptual diagram could be designed. The idea behind the conceptual model is to pull particular information from the brief and model a diagram that only displays the entities and Attributes. The hardest activity to do while modeling a conceptual model is to try and gather all the information from the brief without leaving any important information behind in the the brief.

Logical Design

For the logical design we take the conceptual model and start going in depth by showing each table is linked with each other using crows foot notation and primary and foreign keys. had developed a system of symbols that depict each possible relationship as an entity many only have one relationship or many. However it is also possible for an entity to have an optional participation in the relationship

For example one Human player can have both one or many characters, which is possible depending on the game. I found the Chen’s notation was a great fit for the conceptual model as it is simple and only concerns itself for “one to many” or ” many to many” relationship between entities with diamonds showing the connection. Crows foot notation is better suited for the logical models as it looks deeper into the each entities relationship with simple to understand symbols; such as the one pictured below.

Extended ERD

An extended ERD is used when you have a Entity that has a common attributes that can be shared amount other Entities which are sub classes

As you can see in the above diagram the Employee Entity is a common Entity that holds general Attributes that can be shared by other Entities. At the bottom there are three separate Entities which are sub classes of the Employee Entity. Each sub class have their own distinct Attributes that are not shared amoung the other Entities.

Each sub class can be joint to the common Entity (Employee) either by a

Overlapping means that all the sub classes overlap with each other. such as a Employee can be both a Manager and Sales person.

Disjoint means that an Employee can only be one Sub class Entity.

Union takes all the Attributes and makes one larger Entity

Problems with ERD diagrams

When designing a ERD diagram you may find yourself in a situation where you have fallen victim of “Connection traps”. Connection traps are when there is a misinterpretation of a relationship is some way. There are 2 types of connection traps that may occur when drawing the diagram:

1. Fan trap
2. Chasm trap

In a Fan trap you have a 1 to many relationship between 2 entities joint by a 3rd Entity such as Branch.

The problem identified is that the staff entity and car entity have no clear way of which staff are using each car. So to fix the problem we add a relationship between staff and Car.Now we can monitor the car usage as seen below.

A Chasm Trap

For the above problem we cannot tell from which Branch each staff member works for.

we could argue that in order to track each staff member we only need to look at the relationship between the cars and the staff.

This could be messy as a staff member is not forces to use a car, and if their presence is nor recorded because they have not used a car then no-one will know from which branch the staff member belongs too.

in order to fix the high lighted issue we need to create a relationship between Branch and Staff. Like pictured below.

As we can see in the diagram 1 Branch has many staff. The double lines mean that the relationship is mandated.

Installing MYSQL server on a virtual machine

We had to install MYSQL in a virtual machine , the same virtual software we had to use for Networking.Todd had provided the class with a well drafted instructional manual but some people in class had difficulty following the instructions and poor Todd had to spend all lesson trying to guide people through the process. I had no idea the reason why we had to use a virtual machine for Dat601 but it did not bother me at all as i find virtual machines easy enough to use.

In the virtual machine we had to install windows 10 server edition but we only touched on it briefly. Yet again we had to install the software during lock-down, which took away a lot of the

MYsql server is similar to Mysql workbench with only a few syntax differences which were not too hard to get a grasp on. Having dat601 at the same period as Dat602 was not only difficult to keep track of which subject we where currently undertaking in classs but also trying to navigate the workload between them.