In software engineering, three-tier architecture is a client-server architecture which consists of three layer; presentation layer, functional process logic layer and data layer and is develop and maintain as different module. This architecture is developed by Jon J.Donovan in Open Environment Corporation(OEC), a tools company the founded in Cambridge, Massachusetts.
By dividing application into tiers or layers, developers only have to modify or add a specific logic into the desired layer, rather than rewrite the whole application. This architecture will allows developer to create a more flexible, reusable and maintainable application. This kind of Three-tier layer can also be known as multi-tier architecture or n-tier architecture. Example when user wants to change the text colour from black to red, only the presentation layer will be affected.
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A common example of three tier architecture is ATM (Automated Teller Machine) or Cash Machine. The GUI (Graphical User Interface) where we select services is the presentation layer for ATM. When selecting one of the services that are displayed on the screen, designated event for the services will be invoked. This common set of behaviour is designed in the functional process logic layer. When requesting information such as checking the balance in our bank account, ATM will get the data from the database or application server. This will be the data layer.
Presentation Layer or can also be known as presentation tier, a layer where the presentation or user interface of an application is designed or displayed. In other word, this is the layer which will display all the information that is needed or requested by the user.
Presentation layer is the top most layers in the three-tier architecture. Besides displaying information that is needed by user, this layer will also be used to communicate between other layers by user. For example in Window OS (Operating System), program icon is displayed to allow user to click on it to open the clicked program.
Presentation layer is also part of security where only the needed information will be displayed while other sensitive information will be kept. For example, stock department will need to be able to view and edit the product stock while sales department only need to be able to view the stock that is available.
The presentation layer for Al-Seraj Hire Firm will consist of multiple types. This is because Al-Seraj Hire Firm has different employees that are specialise in different type of aspect of business services in the hire firm. Some employees will only need to display certain information while other may have more or less information. For example in Al-Seraj Hire Firm; purchasing, customer account, sales and marketing will have their own presentation layer.
Functional process logic Layer
Functional process logic Layer is the middle layer in the three-tier architecture. It can also be known business or data access tier, a layer where logic and calculation is taken place. In other word, the business function or business flow will design in this layer.
Functional process logic layer contain the code or function to control the application functionality and also the application business flow. Besides that, it also contains the business logic of the company.
Functional process logic Layer is separated from presentation layer and data layer is to protect the confidentiality and integrity of business flow of a company. Besides that, function is shared by different users. This enables the system to have a consistent and centralized function that can be used by different users. For example, the function or logic to view the stock that is available in the company that is viewed by the stock department the same as what is seen by the sales department.
Other than that, by separating the functional process logic layer, it will enable the administrator or person in charge of the system to easily add in or modify the logic in the system without affecting the other layer.
The functional process logic layer in Al-Seraj Hire Firm will contain the function to indicate whether the customer is a private customer or a business customer. This is because private customer and business customer has their own business logic. Examples of business logic are hiring equipment for private customer is restricted within five miles radius while business customer doesn’t have this restriction. Besides that, business customer will have a 24-hours customer services to replace the faulty equipment while private customer will need to bring in the faulty equipment to replace to working equipment or get a full refund if the equipment is not available.
Data Layer
Data Layer or can also be known as data tier, is a layer where all the data which is inserted by the user is saved. In other word, all information that is entered by the user will be saved in this layer.
Data layer will be responsible to provide the data that is requested from the user. Besides that data can be shared by different users. By doing this, data integrity can be achieved and providing accurate data that is requested by users. This is because the data is saved in a single database which allow different user to get access and request for the data. Besides that, by separating data layer, this will improves the scalability and performance of the system.
The data layer in Al-Seraj Hire Firm will contain the price of the equipment and also the delivery time that is offered by the suppliers. Besides that, it also contains the customer account and also the account packages that are provided by the hire firm.
The five most important user group for Al-Seraj Hire Firm System are Purchasing, Customer Account, Stock Management, Sales and Marketing and Administrator.
Administrator
Administrator is a user group which have the most privileges than any other user group in the system. This is because administrator is a user group that is designed to control or use the full function of the system. Besides that, they also have the privilege to change sensitive data such as the price or discount value for each type of membership account. This user group is used by the owner of Al-Seraj Hire Firm or the person-in-charge of the system.
There are three quality requirements for Administrator user group. The first quality requirements are security requirement. Security requirement is the requirement for the user to be authenticated and authorize as administrator user group. In this user group, the user of the system will need to be authenticated before user is allowed to be authorized as an administrator.
The second quality requirements are modifiability requirement. Modifiability is the requirement for the user to be able to add, modify or delete any data in the database. In this user group, the user of the system will be able to add, modify or delete data in the system. Examples of data in database are discount value for silver membership, gold membership and diamond membership.
The third and last quality requirements are testability requirement. Testability requirement is the requirement for the user to be able to test the whole system with ease. In this user group, user will have the full function that is provided in the system. This also includes other user group function such as stock management and customer account information.
Administrator user group is the top user group in Al-Seraj Hire Firm. This is because any changes that are made by administrator user group, other user group will also be affected. For example, discount value for silver membership which are currently 10%, has been changed to 15%, all user group will have to follow the new discount value.
Customer Account
Customer Account user group is a user group which is responsible for managing customer. In other word, this user group is designed to manage all the type of customer who makes transaction with Al-Seraj Hire Firm. Besides that, this user group also responsible to modify or update customer information and also provide customer services to the customers.
There are two quality requirements for Customer Account user group. The first quality requirement is modifiability. User in this user group will need to be able to change the customer account information as accurate as possible to maintain the productivity of the company. For example, company X has changed their address; the user will need to change the address to the new address to allow other employee to deliver the goods to the destination.
The second and last quality requirement is performance. Performance requirement is the requirement for the user to be able to access or display the desired data in a less amount of work. In this user group, user will need to use the system to search out the suitable customer account in a less amount of time.
Customer account user group is the low level user group in Al-Seraj Hire Firm. This is because all customer details will need to be added into customer account database. As for the data of the customer account, user from the same level will need to take reference to decide which type of customer are they dealing with. For example, a customer has called in and reported that one of their tool has been broke, the user will need to check the customer details to identify whether the customer is a business customer or a private customer.
Sales and Marketing
Sales and Marketing user group is a user group which is responsible for doing sales transaction with the customer. In other word, this user group is designed to record any transaction that is made with customer into the database via Al-Seraj Hire Firm system.
Besides that, this user group will also keep track or produce a financial report according to the sales transaction that has been made in a period of time.
There are three quality requirements for sales and marketing user group. The first requirement is performance. Performance is important for this user group because this is where the income of the Al-Seraj Hire Firm came from. User in this user group will need to have the speed and efficiency to search for tool that is available in time and also the price for it. Besides that, they also need to identify whether it is an existing customer and which type of customer are they in Al-Seraj Hire Firm. For example, two users from this user group will be able to use the system simultaneously to search for customer information.
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The second quality requirement is availability requirement. Availability requirement is important for this user group is because sales of Al-Seraj Hire Firm need to be available during working period. In other word, the system will need to be available when it is needed. For example, maintenance or patch of the system can only be done when there are no people that are using the system to prevent disruption of the sales flow.
The third quality requirement is usability. The information that retrieves by the user from the system can be used or not. In other word, the user will need retrieves accurate information from the system.
Sales and marketing user group is the low level user group in Al-Seraj Hire Firm. This is because user will need to be able to access into the stock management user group information and customer account user group information. This is because they need to identify whether the customer is a private or business customer and is the tool available and what is the price for it.
Stock Management
Stock Management user group is a user group which is responsible for managing stock in Al-Seraj Hire Firm. In other word, this user group is designed to maintain the availability of tool stock in Al-Seraj Hire Firm.
There are two quality requirements for stock management user group. The first quality requirement is usability. The user of this user group will need the accurate information of the stock that is available in Al-Seraj Hire Firm. In other word, user need to get the real number of stock that is available to decide to restock or not. This is because other user group such as sales and marketing will also be able to change the value of the stock in the stock database.
The second quality requirement is modifiability. User will need to be able to change the value or number of stock in the database through the system. In other word, user will add or modify the number of stock in the database via the system that is designed.
Stock management user group is the low level user group in Al-Seraj Hire Firm. This is because user in this user group will need to be able to check for the number of stock that is available and restock it if it is not enough.
Purchasing
Purchasing user group is a user group which is responsible for purchasing new equipment brands based on Al-Seraj Hire Firm equipment categories. In other word, this user group is designed to purchase new equipment brands for the stock management user group.
There is one quality requirement for purchasing user group. The quality requirement is modifiability. The user of this user group will need to be able to add in new equipment information into the database. For example, brand X information will be saved into the stock database.
Purchasing user group is the low level user group in Al-Seraj Hire Firm. This is because user in this user group will need to be able to add in new equipment in the stock database.
Limitation
There are three limitations or design flaw in Al-Seraj Hire Firm system that is designed. The first limitation is only five user group can use the system. This is because the system is designed to be able to allow only five user groups to be using this system.
The second limitation is online ordering transactions are not available. This is because the system is not designed to be to have a shopping cart.
The third limitation is system doesn’t allow add in new membership categories. This is because the system is not design to allow user to add in new membership categories.
The limitation can be changed in the future by adding new function in the system.
Parallel Changeover
Changeover is a method that is used to implement or install the system into an existing or new server. There are four types of changeover; direct changeover, parallel changeover, pilot changeover and phases changeover. The changeover method that can fulfil the requirement of Al-Seraj Hire Firm is parallel changeover.
Less expensive.
Lower risk of error or failures.
The first part is stock management module and purchasing module. The second last part is customer account and sales and marketing. In the period of implementation, user acceptance test is given to check whether the system fulfil their requirement. Training is given if the system is accepted by the user.
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