We've a big data management website used by several property. Some of our customers have downtime (they can't access net for an hour or two). We want our site to support offline data viewing and inventory management (typical data search and add/remove) and when the user goes online we can sync the changes back to our central database. Customers use several platforms like Windows, iOS, etc.

We've been looking into several different options, here are the major choices -

Develop offline web app supported in HTML5. Develop a 'fallback' mechanism and interact with data from the app cache as explained in here (http://www.htmlgoodies.com/html5/tutorials/introduction-to-offline-web- applications-using-)

Develop a desktop based cross platform solution. I remember the old MONO which has been popular. Here's a post (What do you suggest for cross platform apps, including web cross-platform-apps-including-web) and another one (Technology choice for cross platform development (desktop and phone)? platform-development-desktop-and-phone?rq=1)

I realize the the desktop solution might be hard to maintain and result in some compatibility issues and demand test environments.

Can HTML5 handle moderate to high level complexity and data flow? Or would it be better to rely on a desktop based app for better scalability & performance?