Mobile Application Architecture Series – Design Considerations

Mobile applications inherit various challenges which need to be considered while designing on any platform (Microsoft / Symbian / OS X etc). The following section tries to address various design guidelines for a mobile application development. Technology stack considerations would be the next in this series of blogs.

A mobile application will normally be a multi-layered application comprising user experience, business and data layers. When developing a mobile application, you may choose to develop a Thin-Client or Rich-Client. If you are building a rich client, the business and data layers will be located on the device itself. In Thin-Client, the business and data layers will be located on the server.

Design Considerations:

Follow these design guidelines to ensure that the application meets your requirements and performs efficiently in mobile world.

1)      Thin-Client or Rich-Client or RIA.  If your application requires local processing and must work in an occasionally connected scenario, consider designing a Smart (thin) client. But, a Rich-Client application will be more complex to install and maintain. If the application can depend on server processing and will always be fully connected, consider designing a Thin-Client. If your application has a rich user interface, only limited access to local resources, and portability to other platforms is required, then RIA would be a good choice (eg. ETrade).

2)      Device Types to Support: While choosing which device types to support, consider screen size, screen resolution (DPI), CPU performance characteristics, available memory and storage space (inbuilt & external) and Integrated Development Tool availability. On top of the above, we need to consider the User Requirements and Organizational Constraints / Guidelines. Any additional components such as GPS and Integrated Camera may influence your choice of application type and device type.

3)      Connectivity: The real time connectivity requirement between the mobile device and Gateway would highly influence the decision of whether to go for Thin-Client or Rich-Client or RIA. If an application requires an intermittent network connection, our design approach should properly handle caching, state management and data access mechanisms.

4)      UI design considerations: Mobile devices requires simple UI in order to work within the constraints imposed by the device hardware such as memory, battery life, different screen sizes and their orientations and network bandwidth.

5)      Layered Architecture: Depending on the application type, multiple layers may be located on the device. Use the concept of Layers to maximize the separation of concerns, and to improve reuse and maintainability for your mobile application. However, aim to achieve the smallest footprint on the device by simplifying your design compared to a desktop or web application.

6)      Security: Designing an effective authentication and authorization strategy is important for the security and reliability of your application. Mobile devices are usually designed to be single-user devices and normally lack basic user profile and security tracking beyond just a single password. Mobile applications can also be especially challenging due to connectivity interruptions.

7)      Caching: Use caching to improve the performance and responsiveness of your application, and to support operation when there is no network connection. Use caching to optimize reference data lookups, and to avoid network round trips. When deciding what data to cache, consider the limited resources of the device; you will have less memory available than a PC.

      Communication: Device communication includes wireless communication (over the air) and wired communication with a host PC, as well as more specialized communication such as Bluetooth or Infrared Data Association (IDA).  When communicating over the air, consider data security to protect sensitive data from theft or tampering.

9)      Performance Considerations:

a.       Design configurable options to allow the maximum use of device capabilities. Allow users to turn off features they do not require in order to save power.

b.      To optimize for device resource constraints, consider using lazy initialization.

c.       Optimize the application to use the minimum amount of memory. When memory is low, the system may release cached intermediate language (IL) code to reduce its own memory footprint, return to interpreted mode, and thus slow overall execution.

d.      Consider using programming shortcuts as opposed to following pure programming best practices that can inflate the code size and memory consumption. This decision should be a thoughtful one as it may contradict the design principles of OOPS and maintainability.

e.      Consider power consumption when using the device CPU, wireless communication, or screen while on battery power. We should balance power consumption with performance.

In my view, the above listed considerations are only a subset of complete list, but tried to address the key areas in it. One basic design approach for most of the mobile applications is “avoid BDUF”, Big Design Up Front, which recommends design evolving over time and avoid making a large design effort prematurely.

Sreenivasa Rao Pilla Architecture & Design, Mobile Architectures Architecture, Design Considerations, Mobile, Mobility