Application Architecture Guide 2.0 BETA 1 - Willy .Net

applications over the Internet or intranet, consider building a service. If you do not require a
rich interactive UI, you want to deploy over the Internet, and you want to maximize
platform and browser independence, consider building a Web application.
• How to design a mobile application
Applications for mobile devices fall into two categories: Web applications and rich client
applications. The decision on the type of application you design can be based on the
connection requirements, resource requirements, and UI requirements. If your users do not
need to work disconnected, and your performance requirements can be met with regard to
the network bandwidth constraints of your users, consider a Web-based mobile client.
Another option for a connected scenario, where a rich interface is required, is a Rich
Internet Application. If your users must work in a disconnected or occasionally connected
way, or if you require direct access to the device hardware resources, consider a mobile rich
client. Consider screen size and format, CPU performance characteristics, memory and
storage space, development tool and environment support, as well as user requirements
and organizational constraints, when choosing which device types to support. Mobile
devices require a simpler architecture, simpler UI, and other design decisions to work within
the constraints imposed by the device hardware. Keep these constraints in mind and design
specifically for the device instead of trying to reuse the architecture or UI from a desktop
application or a Web application. Every design decision should take into account the limited
CPU, memory, storage and battery life of mobile devices. In addition, most mobile
applications must work when a network connection is intermittent or not available. Design
your caching, state management, and data access mechanisms with intermittent network
connectivity in mind.
• How to design a rich client application
Rich client applications offer complex data visualization, superb text flow content rendering,
access to local resources and devices, and a rich and dynamic interactive experience. Rich
Client applications range from thin interfaces that overlay business layers and service layers,
to complex applications that perform most of the processes themselves and just
communicate with other layers to consume or send back information. Various technologies
are available to design rich client applications. These technologies include Windows Forms,
Windows Presentation Foundation (WPF), XAML Browser Applications (XBAP), and Office
Business Applications (OBA). A typical rich client application design focuses on the
separation of UI from processing, on the user interface, on the handling of business rules,
and on communication between layers. Separate the presentation logic from the interface
implementation using design patterns such as MVC and Supervising Controller. Separating
UI rendering from UI processing eases maintenance, promotes reusability, and improves
testability. Design to provide a suitable and usable interface. Take into account features
such as layout, navigation, choice of controls, and localization to maximize accessibility and
usability. Extract business rules and other tasks not related to the user interface. A separate
business layer should handle tasks not directly related to presentation, or related to
collecting and handling user input. Loosely couple your client to any remote services it uses.
Use a message-based interface to communicate with services on separate physical tiers.
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