The purpose of an information system is to process data and extract useful information for its users. As a result, data is the most important part in an information system. For this purpose the technique of data modeling has been developed, in order to assist system analysts and developers to design and develop efficient data models based on the extracted user requirements. Data modeling consists of some basic concepts which are common throughout the most used data modeling notations. Whitten and Bentley mention entities, attributes and relationships as the basic concepts of data modeling (Whitten And Bentley, 2007).

An entity is a concept that attempts to describe the real world. Entities are persons, objects, facts, actions or abstract concepts for which data needs to be gathered. Taking as an example a business, the entities that would compose the data model could be the employees, the managers, the offices, the salaries ...

The input systems design is the phase in the software development lifecycle when the analyst decides the way the data will be inputted into the system. A software system is, in brief words, a system which processes input data and produces an output. So, in order to achieve a correct output it needs to get the correct data as an input. This fact reveals the importance of the system input design phase. As the technology evolves, a greater number of input methods becomes available. Most of them are used by users so they must be designed based on the human behavior.

Input systems design is a concept closely related to usability and user interface design. These three factors consist the user experience term. Today, we can spot a large number of system data input methods into software systems. The most common of them are the keyboard, the mouse, the touch ...

Nowadays the business environment is in a continuous move. Changes in technology happen more often and needs and requirements are modified frequently. So, since the information systems are here to solve specific problems and have specific requirements, it is natural to need changes and modifications in order to adapt to a modern environment. "The variable information technology (IT) environments bring new challenges for legacy systems in the modern world. This need unlikely will be fulfilled by redeveloping legacy systems, because legacy systems are crucial for companies, and therefore, they cannot afford to write them off."(Huang, Hung, Yen, Li And Wu, 2006, p.1). So, updates to software systems are a frequent event and new updated versions are often released. But as this process of updating the software continues, it is possible that the overall quality of the system will degrade. Here is where the system reengineering or refactoring comes ...

Until the early eighties, when the focus of information systems was mostly the processing of arithmetic data, the role of a systems analyst was clearly technical(Kiountouzis, 1997). Nowadays, with the evolution of the information systems, the modern corporate environment is changing drastically. Modern businesses are closely dependent on the information and the information workflow and are heavily relied on the accuracy and the solidity of it. As a result, the role of a system analyst and a system manager becomes of major importance. The role of a system analyst now is to study business problems and opportunities and transform business and information requirements into specifications for information systems that will be implemented. System analysts are the people who initiate change within an organization (Whitten and Benltey, 2007).

The strategic mission of the company is usually set by the decision makers and the managers after a careful examination and evaluation ...