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Graphical user interfaces have become a familiar part of our software landscape, both as users and as developers.
Looking at it from a design perspective they represent a particular set of problems in system design - problems that have led to a number of different but similar solutions. My interest is identifying common and useful patterns for application developers to use in rich-client development.
I've seen various designs in project reviews and also various designs that have been written in a more permanent way. Inside these designs are the useful patterns, but describing them is often not easy. Take Model-View-Controller as an example. It's often referred to as a pattern, but I don't find it terribly useful to think of it as a pattern because it contains quite a few different ideas.
If this doesn't cause enough confusion you then get the effect of misunderstandings of MVC that develop through a system of Chinese whispers.
In this essay I want to explore a number of interesting architectures and describe my interpretation of their most interesting features. My hope is that this will provide a context for understanding the patterns that I describe.
To some extent you can see this essay as a Context data flow diagram essay of intellectual history that traces ideas in UI design through multiple architectures over the years. However I must issue a caution about this.
Understanding architectures isn't easy, especially when many of them change and die. Tracing the spread of ideas is even harder, because people read different things from the same architecture.
In particular I have not done an exhaustive examination of the architectures I describe. What I have done is referred to common descriptions of the designs. If those descriptions miss things out, I'm utterly ignorant of that. So don't take my descriptions as authoritative.
Furthermore there are things I've left out or simplified if I didn't think they were particularly relevant. Remember my primary interest is the underlying patterns, not in the history of these designs. There is something of an exception here, in that I did have access to a running Smalltalk to examine MVC.
Again I wouldn't describe my examination of it as exhaustive, but it did reveal things that common descriptions of it failed to - which even further makes me cautious about descriptions of other architectures that I have here.
If you are familiar with one of these architectures and you see I have something important that is incorrect and missing I'd like to know about it. I also think that a more exhaustive survey of this territory would be a good object of academic study.
Forms and Controls I shall begin this exploration with an architecture that is both simple and familiar. It doesn't have a common name, so for the purposes of this essay I shall call it "Forms and Controls".
It's a familiar architecture because it was the one encouraged by client-server development environments in the 90's - tools like Visual Basic, Delphi, and Powerbuilder. It continues to be commonly used, although also often vilified by design geeks like me. To explore it, and indeed the other architectures, I'll use a common example.
In New England, where I live, there is a government program that monitors the amount of ice-cream particulate in the atmosphere.
If the concentration is too low, this indicates that we aren't eating enough ice-cream - which poses a serious risk to our economy and public order. I like to use examples that are no less realistic as you usually find in books like this.
To monitor our ice-cream health, the government has set up monitoring stations all over the New England states. Using complex atmospheric modeling the department sets a target for each monitoring station. Every so often staffers go out on an assessment where they go to various stations and note the actual ice-cream particulate concentrations.
This UI allows them to select a station, and enter the date and actual value. The system then calculates and displays the variance from the target. The UI I'll use as an example. As we look at this screen we can see there is an important division as we put it together.
The form is specific to our application, but it uses controls that are generic. Most GUI environments come with a hefty bunch of common controls that we can just use in our application.Data stores are not shown in the context diagram because they contained within the system and remain hidden until more detailed diagrams are created.
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A diagram is a symbolic representation of information according to some visualization technique. Diagrams have been used since ancient times, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three-dimensional visualization which is then projected onto a two-dimensional surface.
The word graph is sometimes used as a synonym for diagram. Essay on Context Data Flow Diagram TYPES OF DATA FLOW DIAGRAM: LOGICAL DFD PHYSICAL DFD Data Flow Diagrams (DFDs) are categorized as either logical or physical.
A logical DFD focuses on the business and how the business operates. It describes the business.
Among science fiction stories with space flight, the overwhelming majority are about combat, both between spacecraft and between futuristic ground troops.
A Data Flow Diagram Dfd Information Technology Essay. Print Reference this. Published: 23rd March, (exploded diagram of context diagram) shows how the system interacts. It is important to first draw context-level data flow diagram first before the level 0 to show all basic operations in the system.
(Kevin Bowman, ).