Database Modelling

Table of Contents

1. Requirements Modelling 1

1.1. Context Diagram вЂ" Current System 1

1.2. Diagram 0 DFD вЂ" Current System 2

1.3. System Requirements 3

1.3.1. Outputs 3

1.3.2. Inputs 4

1.3.3. Processes 4

1.3.4. Performance 5

1.3.5. Controls 5

1.4. Scalability Issues 6

1.5. Functional Decomposition Diagram 7

2. Data Modelling 8

2.1. Context Diagram вЂ" Proposed System 8

2.2. Diagram 0 DFD вЂ" Proposed System 9

2.3. Data Flows and Data Stores 10

2.4. Data Elements in Data Stores 12

1. Requirements Modelling

1.1. Context Diagram вЂ" Current System

Figure 1: Context Data Flow Diagram вЂ" Cornucopia College Housing System

Accommodation Providers must contact the College Housing office to advise them of their listing. The Accommodation Providers are not able to directly add their listings to the binders.

1.2. Diagram 0 DFD вЂ" Current System

Figure 2: Diagram 0 DFD вЂ" Cornucopia College Housing System

1.3. System Requirements

Explain system additions вЂ" landlord database, landlord add data вЂ" not at this stage as it requires authentication system

The preliminary investigation has identified several requirements for the new system. The features and characteristics that have been highlighted are that it must be:

• Easy to access;

• Tamper proof;

• Up to date;

• Easy to maintain.

The current binder system requires prospective tenants to visit the Cornucopia College Housing office and manually search through the binders. This does not make the system very accessible to people requiring accommodation that cannot attend the office. The current system is difficult for someone to filter out the listings that are not suitable for them. The new system should allow people to search for listings that suit their requirements.

During the investigation it was noted that unauthorised removal of listings occurs. Listings are removed from the binders by people seeking accommodation so that they reduce the competition for the desirable properties. The new system should only allow Cornucopia College Housing office staff to remove listings.

The current binder system may store a single listing in up to 15 different binders. When a listing is to be removed from the binders it is sometimes missed in one or more of the binders. This leads to an inconsistent system that contains incorrect information. The new system should store a listing once, thereby allowing for it to be removed from all searches and listings when it is rented.

The current hand-written listings are susceptible to error and the omission of important information. Maintaining the listings may require the alteration of 15 different forms which may result in additional errors and inconsistencies. Cornucopia College Housing office staff are required to search through all 15 binders each month to remove listings that are older than two months. The new system should allow the staff to enter the listing details once, using a process that validates the information provided. The system should automatically purge listings that are older than two months and provide the office staff with a report of these listings.

1.3.1. Outputs

The following outputs have been identified:

• Up to date listings;

• Restricted listings;

• Ordered listings;

• Searchable listings;

• Accessible via the Internet.

Achieving More Effective Outputs

The current system requires the person looking for a rental property to search through every listing to determine if it meets their requirements. A person with a pet is not interested in properties that do not permit pets. A rental that does allow pets may not be suitable due to rent value, lease term, availability date and many other criteria. The output from the new system should allow renters to search for listings based on criteria that are applicable to them. They should be able to search for rentals that cost between $60 and $80 per week, allow pets, have a six month lease term and that are available now.

1.3.2. Inputs

The following inputs have been identified:

• College vacancies details;

• Private vacancies details;

• Identification details;

• Search options.

Achieving More Effective Inputs

Currently, the details of each rental are recorded on a sheet of paper which is inserted into a binder. Depending on the target audience, each rental may be inserted into 15 different binders. Some details for the vacancy may be omitted or erroneous. More effective input of this information can be achieved by data entry validation and providing a single store for the rental information.

Data entry validation is used to ensure that mandatory information is entered, such as a unit number when the type of rental is unit. It is also used to ensure that the information is a valid format, for example, a telephone number must be a ten digit numeric.