An Object Oriented Approach to the Design of Graphical User Interface Systems

An Object Oriented Approach to the Design of Graphical User Interface Systems
Nowadays, the usage of personal computers, mobile devices and internet among the general population, so the importance of easy to learn user interfaces has risen in recent years. The development of Graphical Interface Systems becomes important. These systems will make easy to user activities and communication of particular systems. The first and main feature of User Interface System is that manages the communication between user and application. So in the process of developing these systems, the object oriented programming features and techniques will make the design characteristics of interface systems like interactivity, flexibility and usability. Applying object-oriented methodologies to UI design can help to achieve this goal. To develop user interfaces, first identify the task to particular program function translation. It also involves identifying the object, problem space and associated functions, objects and attributes for the system. The main purpose of using object oriented approach in designing user interfaces because object programming allows for reusability,modularity and data privatization.

modern graphical user interfaces are object-oriented; the user first accesses the object of interest and then modifies it by operating upon it. There are several reasons for going with an object-oriented interface approach for graphical user interfaces. One is the desire to continuously depict the objects of interest to the user to allow direct manipulation. For example in linux machines to delete the file or line the user would first remember the keyword for deletion and issue a delete command, but this can be achieved by creating icons in user interfaces. Icons are good and representing the objects .
Modelling and designing of the graphical interfaces is big issue. In most of the current systems are designed with old input models like GKS and phigs. They classifies the logical input values with data types in developing the application. But comparing with windows systems like Athena X toolkit, its completely based on external appeareance like drop down menu, a buttion, a pen or pencil to draw. These functionalities composed from layout designs. All these provide relationship between input and output of program functionality. Later in other modellings such as small talk and PAC, do not provide relationship among user input values and output functionality.
The graphical interaction as composed of three components the collection, the picture, and the measure. The examples for these graphical interfaces environments are like geometrical applications. In some applications will show different output representations with same data like in pie chart and bar chart. When they are active there is an input trigger associated with the measure to indicate when its function has to be applied and an output trigger indicating when the collection has to be updatedin order to send new graphical information to the picture and the measure. For example in a pop up menu we can consider the button press (that implies the menu appears) as an output trigger, and the button release (that implies that the current selected element is sent to the application) as an input trigger. Triggers can be considered as boolean functions that when are verified generate the control signal.
Sather has parameterized classes, object-oriented dispatch, statically-checked strong (contravariant) typing, separate implementation and type inheritance, multiple inheritance, garbage collection, iteration abstraction, higher-order routines and iters, exception handling, assertions, preconditions, postconditions, and class invariants. Sather programs can be compiled into portable C code and can efficiently link with C object files.

There are six kinds of variables in Sather: the shared, constant, and object attributes of classes, and the arguments, local variables, and return values of routines. The four kinds of type specifications are: non-parameterized, whose features are completely specified by the class specification;parameterized, where the name of the class is followed by the specification of the type of the parameter; type parameter, where the type of the parameter is specified by a type variable, when a parameterized class is used, the type variable is instantiated and the compiler generates appropriate calls; dispatched, where the type will be dynamically dispatched and it can be a subclass of the given class, there is a runtime mechanism that chooses the routine to be called depending on the runtime type of an object.

The traditional approach to object-oriented user interfaces is to associate the graphical objects visible from the user with an underlying object representation. Here we aim to a task-object association. This means that we want to make it possible to design user interface systems by creating instances of objects that are characterized more by their semantics than their appearance. The four basic tasks are choice, position, quantifier and text.