My First Cloud Application's Design

Structure Diagram as following:

Questions list:

1. Skydrive Integration

> Based on the MSDN community, it is possible to upload the file to Skydrive. Then, how to lock the file?

2. Embedded SQL Engine Choice. 

> SQLite, Can it directly using Web SQL from HTML5?

> SQLite. If it can't use Web SQL due to Browser's Limitation (Firefox can't support Web SQL), how about copy the Cloud file to local file and only upload them back to Cloud? Performance?

> SQLite and SQLCE: Besides the native SQL operation provided by HTML5, we have to use C++/.NET in HTML5? Does the ASP.NET is the only choice? How about the Version supporting? SQLCE 4 supports .NET 2.0?

3. Encryption

> How to control the Encryption for sensitive data.

4. Any other question?