Task : Modelling Basics
Overview of business case:
Handy-Trady Hire (HTH) is a home repair company that employs several contractors who specialise in different areas. Contractors have a specialisation in any of the following areas:
Interior & Exterior painting
HTH started as a small family business and for the past five years has been managing their business activities using an Excel spreadsheet. With view to their expanding business and under the new management, they decided to investigate the option of implementing a database system. Accordingly, they hired you to design a relational database to better track and record their operational data.
HTH discovered business rules/constraints for your ERD:
- A customer calls HTH to request a home repair job:
Details about the customer and the requested job need to be recorded. (2 marks)
- Each tradesperson specialises in only one trade, and details of their trade and the date acquired need to be kept on record. (2 marks)
- HTH has several trucks (including equipment) and allocates a truck for each tradesperson to do a job. Although some tradespersons have their own truck and equipment and advise HTH about this, so not to be assigned a truck. (2 marks)
- A requested job may require different specialisation depending on the job type – that is, a job may require more than one tradesperson to complete. (4 marks)
- At a later interview with the manager you learnt that HTH appoint one of the tradespersons to supervise others and oversee the work done by the other tradespersons. (1 marks).
- Also HTH wants to keep records of how the customer was referred to them – by what source (ie- TV add, Friend, Internet, etc.) (2 marks).
- Customers have the option to make partial payments for a service, as long as they pay no later than one week after the completion of any service — Details about each payment relating to a service, amount of payment and date need to be recorded. (2 marks)
Create an ERD for each of the above statements that describe the current business rules for HTH. For each new statement being the business rule, extend the ERD to include the additional business rule in the ERD (created in previous point ‑ for example; B will include A&B, C will include A, B & C, etc.)
Use Crows Foot notations and include all the following in each part:
- All entities with Primary key and any foreign key attributes;
- The relationships between entities;
- The cardinality and optionality of each relationship;
- Any M:N relationships are be resolved to 1:M relationships
NOTE : Comprehensive and accurate ERD that contains all entities, PK and FK, attributes, associative entities included if required, all relationships shown and identified with correct cardinality and optionality.
All screenshots that are required should be captured and inserted into the document in the appropriate position to show that you have completed the requirement.
Task : Modelling & Normalisation
Using the given table/relation, do the following:
- Draw a dependency diagram to show the functional dependencies in the relation
- Decompose the following table into a set of 3NF relations
- Draw a relational schema for your 3NF relations and show the referential integrity constraints
- Manually drawing the dependency diagrams is not acceptable.
This assessment item is designed to test your understanding of the normalisation process based on existing data in order to minimise redundancies and data anomalies.
The marking criteria for this assignment are:
|Decompose relation into 3NF and show relational schema for each relation and referential integrity constraints||All relations in 3NF and all partial and transitive dependencies removed, each relation shows correct referential integrity constraints|
|Create an ERD & show all entities, PK & KF attributes,
relationships, cardinality & optionality
|Comprehensive and accurate ERD that contains all entities, PK and FK attributes, associative entities included if required, all relationships shown and identified with correct cardinality and optionality|