One of the main reasons that businesses often opt for a website-based approach is to avoid having to build many products for the platforms they wish to support. We're seeing a similar approach to mobile application development: as more platforms enter the market, developing native apps becomes an overhead that many businesses can't afford. They opt for the web-based approach or hybrid app, where the user believes they're installing a native app that's really just a website packaged into a download. While this can be good enough for simple applications with basic data processing, it is often not going to meet user expectations. Additionally, the interaction paradigms for a web browser are usually different to that of the system applications around it. If the user expects an application to behave in a certain way, then an embedded web browser could prove to be a confusing experience.

The biggest challenge in delivering a large application through web technologies (through a browser or downloaded application) is achieving good performance. As a browser is designed primarily for information exchange, it isn't well suited to large data processing or complicated graphical representations. When delivered through a web browser, much of this can be performed by a remote server that has the capacity to run complex calculations and return the summary to the user. Unfortunately, when you're running a local application, this cannot be relied upon and users expect immediate results in their application (remember, this is not a browser window with lots of open tabs to browse while waiting). Additionally, recall one of the benefits of web-based delivery—the chance to update the software continually without distribution issues? While that may be great for development, it's possible that your customers don't want the interface to be changing all of the time; they want to be in control of when (and if) to update their systems.

In applications where there's a lot of computation to run or complicated graphics to display, most web apps will struggle to run as fast as a user expects. Native applications, which are compiled for the computer they're used on (and will have been downloaded in advance, so no waiting), are currently the best way to get high performance. There are various virtualization technologies that aim to provide near-native performance with a single application (for example, Java), but this is not always appropriate or sufficient, and often suffers side effects such as long start up times or huge downloads. As you've chosen to read this book, you'll probably already be aware of another approach: a language that allows you to write a single application but have it compile to a high performance native application for any platforms you wish to support.