User interface complexity
A user interface is the means in which a person controls a software application. A user interface should provide the user with an easy experience, allowing them to interact with the software in a stress-free and natural way. The GUI (graphical user interface) is a program that contains graphical controls which the user can select with a keyboard or mouse. “The GUI complexity is the most important value to consider when selecting a technology for user interface classes. (Rayhan, 2003)”. To decide on the complexity of the user interface it is important to consider all possible user interfaces for the ePS system. We should also reflect on a variety of categories which include simple data input, static view of the data, customisable views, dynamic view of the data and interactive graphs.

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The simple data input allows the user to enter data into the system. The static view of data can be either a table, tree or graph that is not affected by the changes in the system data. “The customisable view allows the user to customise the appearance of static data without making a new request to the server. The dynamic view of data is automatically refreshed to stay current while the underlying system data changes. The interactive graphs are similar to dynamic views. The graphical view is automatically updated as the underlying system data changes (Rayhan, 2003).”
Below is a list of user interfaces for the ePS system:

Login user interface: The login user interface allows the user to enter their username and password to gain access to the system.
Create E-Prescription user interface: The Create E-Prescription user interface allows the general practitioner user to create an E-Prescription for a patient, view their personal details and view their medical history.
Dispense medicine user interface: The dispense medicine user interface allows the pharmacist user to view the patients E-Prescription, check if the medication is in stock and dispense the medicine.
Manage ADR report user interface: The manage ADR report user interface will load a ADR report form on a web page for the user to enter in their adverse drug reaction to a particular medicine.

Deployment constraints for user interfaces
The deployment constraints are as imperative as the complexity of the user interface. When considering deployment constraints it is essential to have categories in which to compare. The following deployment constraints can occur within our ePS system:

Any web browser on the internet: This deployment constraint must allow the user interface to perform on any web browser on any computer. The web browser Opera does not support Java which means that all images and much less dynamic HTML, so the user interface would be presented in text form only.
Late-Model web browser on the internet: If each web browser is no more than a few generations old then we will also know that the computer is also no more than a few generations old.

Number and types of users
The number and type of users influence the technology selection in two ways. One influence being that a large number of users can force the technology for the entity, control and lifecycle classes to balance well. A large number of users can also encourage the selection of user interface technology. A larger audience makes straightforwardness of deployment and maintenance costs major factors.

Small number of dedicated users: These are a small group of users who can help to outline the system and who profits from the system. Since these groups are willing to invest their own time to learn the system, functionality is the main priority.
General use within an organisation: In regards to the system, this group of users are generally much larger, but they can be less motivated. These types of systems tend to support the organisation rather than contributing to the business. For example time tracking and benefits management.
Large audience with high interest: The ePS system must have a large audience that are extremely involved. These users may be unconnected from one another. The users may log on to the system to exchange information e.g. the E-Prescriptions or to collaborate information about the patients and the medicine.
Huge audience with low interest: In terms of the ePS system, it must attract and serve indecisive audience. If the ePS system runs slowly and wastes the audiences time it will cause the audience to be disengaged.

Available bandwidth
The bandwidth available is also another crucial factor when selecting technologies. Certain groups of technologies can allow developers to meet low bandwidth restrictions. However, other technologies make bandwidth constraints worse. The categories for bandwidth restrictions are as follows:

Dial-Up connection: The dial-up connection is now the least common type of connection to the internet. However, Dial-Up connection is suitable for systems that let users view text, images and to enter data. This would be suitable for the ePS system when the user logs in and loads the ADR report form. The ADR report will load up on a web page.
Fast internet connection: Fast internet connections consist of digital transmissions over phone lines, cables and satellite transmissions. This is mainly to enable a quicker internet connection.
Dedicated network between client and server: This type of connection will allow the client and serves to exchange data at considerably high speeds.

Types of System interface
The technology for a system interface is determined by a current outer system. If an external system is not available, you must describe the system interface and then select an applicable private technology. System interfaces are divided into the following three categories:

Data transfer: Many system interfaces exist merely to transfer large lumps of information from system to system. These interfaces are referred to as electronic data interchange.
Services through a protocol: This system interface will allow a system to make requests through an agreed protocol. The server will allow a system to validate itself and request data by sending predefined codes.
Direct access to system services: This system interface will allow a client system to directly call selected methods in the server. The server exposes these certain methods for remote access.

Performance and Scalability
The performance and scalability requirements are becoming one of the most important features in the selection of technology. Performance must be balanced against data integrity and any multiuser system and there aren’t many single user systems left. The performance and scalability factors are usually found by inspecting the class diagrams and sequence diagrams from the analysis model. The following are the three main categories that may affect the performance and scalability:

Read-only: Certain systems only allow the user to view system data, but do not allow them to update it.
Isolated updates: In most systems the user is allowed to change the systems data and the changes do no conflict with one and other.
Concurrent updates: In some systems many users change the systems data, but with some changes affecting the same data.

The following sections below describe the performance and scalability factors for each use case in the ePS system:

Create E-Prescription use case: In the Create E-Prescription use case the system retrieves and displays the patient’s record. After the user enters the diagnosis and the system must update the current data with the new data. This use case is described as “Isolated updates” or “Concurrent updates”.
Dispense medicine use case: In the dispense medicine use case the system retrieves and displays the patients E-Prescription. After the user checks the stock levels and dispenses the medicine the system must update the status to “Complete”. This use case is either described as “Isolated updates” or “Concurrent updates”.
Record ADR use case: In the record ADR use case the system retrieves and displays the ADR entity objects. After the user updates the entities the system must update the data with the new data. This use case is either described as “Isolated updates” or “Concurrent updates”.
Login use case: In the login use case the system locates the user entity object that corresponds to the actual user. Once the object is located, the system must determine whether the username and password is valid. The means the systems needs to read the username and password from some sort of persistent store. No data will be updated therefore the “Read-only” description is appropriate.