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As web applications have become more complex, they have begun to push the boundaries of both the capabilities of the browser and the usability of the application. As their popularity grows, these issues become more apparent and important and highlight the fact that there are still a number of significant issues for both developers and end-users when deploying and using applications within the browser.
The web browser was originally designed to deliver and display HTML-based documents. Indeed, the basic design of the browser has not shifted significantly from this purpose. This fundamental conflict between document- and application-focused functionality creates a number of problems when deploying applications via the browser.
Applications deployed via the browser have their own user interface, which often conflicts with the user interface of the browser. This application-within-an-application model often results in user interfaces that conflict with and contradict each other. This can lead to user confusion in the best cases, and application failure in the worst cases. The classic example of this is the browser's Back button. The Back button makes sense when browsing documents, but it does not always make sense in the context of an application. Although a number of solutions attempt to solve this problem, they are applied to applications inconsistently, and users may not know whether a specific application supports the Back button or whether it will force their application to unload, causing it to lose its state and data.
Due in part to the web security model (which restricts access to the user's machine), applications that run in the browser often do not support the types of user interactions with the operating system that people expect from applications. For example, you cannot drag a file into a browser-based application and have the application act on that file. Nor can the web application interact with other applications on the user's computer.
RIAs have tried to improve on this by making richer, more desktop-like interfaces possible in the browser, but they have not been able to overcome the fundamental limitations and separation of the browser from the desktop.
Because web applications are delivered from a server and do not reside on the user's machine, web applications are primarily an online experience. Although attempts are underway to make offline web-based applications possible, they do not provide a consistent development model and they fail to work across different browsers, or they require users to install additional extensions to the browser. In addition, they often require users to interact with and manage their application and browser in complex and unexpected ways.
Finally, as applications become richer and more complex and begin to push the boundaries of JavaScript and DHTML, developers are increasingly faced with differences in browser functionality and API implementations. Although these issues can often be overcome with browser-specific code, they lead to code that a) is more difficult to maintain and scale; and b) takes time away from function-driven development of feature functionality.
Although JavaScript frameworks are a popular way to help address these issues, they can offer only the functionality provided by the browser, and often they resort to the lowest common denominator of features among browsers to ease the development model. The result for JavaScript- or DHTML-based applications is a lowest common denominator user experience and interaction model, as well as increased development, testing, and deployment costs for the developer.
The fact that web applications have flourished despite these drawbacks is a testament to the attractiveness of having a platform with a good development model that has the ability to deliver applications to multiple operating systems. A platform that offered the reach and development model of the browser, while providing the functionality and richness of a desktop application, would provide the best of both worlds. This is what Adobe AIR aims to provide.
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