Selected ingredients in end-user programming

In the area of human computer interaction, over the last twenty years, we have witnessed considerable progress in an ever-increasing bandwidth from the computer to the user. Application screens evolved from static text only screens to interactive GUI screens. These screens contain numerous graphical element or "widgets", supporting multiple data types, such as text, voice, image, and video. The widgets can range from simple ones like a combo box or slider to more complicated OCX's such as interactive graphs or maps.On the other hand, the tools to program this application are still in the domain of programmers. Although there has been much progress in various RAD tools, visual language and 4GL to improve ease of use, they still mostly target programmers. We believe that in order to allow end-users to develop their own advanced UI applications, it is necessary to create higher-level application abstractions or 'algebra' for stating the application in a declarative manner. This can be compared to the relational algebra operators in the data base area. They were created as abstractions for data base queries, enabling end users to express their own queries in a declarative manner. In doing so, bugs are minimized and program modifications and maintenance becomes trivial. In this paper, we will motivate the reader to see the need for these abstractions and classify them into categories, emphasizing areas ripe for further research.