How to open existing database in WebSQL?

What are some approaches to support disconnected mode operations for an existing database-driven web application?

• For the purpose of this question the use case is a database-driven web application supporting CRUD functionality for a customer relationship management (CRM/ERP) system. Currently the interaction is through an always-connected desktop browser. Now the desire is to support data entry from a mobile smartphone (initially android). The smartphones will occasionally be in areas of no network coverage and uninterrupted data entry is desired. When the device returns to coverage, any pending created items should be submitted and any new/updated items on the server should be downloaded. What are some approaches to "retro-fit" a disconnected mode operation for such a use case? The web application is a tested, stable, pre-existing PHP/MySQL application so changes to its database technology (i.e swapping MySQL for CouchDb) itself are not desirable but a layer can be build on top.   On the mobile application side, all options are possible.  We are hoping to use a hybrid html5 application so can mix and match native and web components on the client. Conflicts are possible but likely to be rare in our specific environment but a solution should address those and provide a way to flag them so the user can take remedial action. The application itself has a responsive design and can use HTML5 capabilities for application cache etc - it's just the data synchronization that is an issue. I suspect if someone is addressing this in a generic way, a whole family of existing web apps would become disconnected-mode friendly.

• Answer:

  As you know, html 5 supports local storage (here is some info, but you can find more yourself http://www.ibm.com/developerworks/xml/library/x-html5mobile2/) while it may seem oversimplified, here is pseudo-code. Your requests to web server need to be done through JS try catch. var isLastRequestFailed = false try {    isRequestSuccess = callWebService(Data)    if isRequestSuccess & isLastRequestFailed    {       isLastRequestFailed = false       data = ReadFromLocalStorage       while (data != null)       {           callWebService(data)          data = ReadFromLocalStorage       }    } } catch {    if errorType = noConnection    {       isLastRequestFailed = true       if not IsInDB(data)       {          writeToLocalStorage       }    } }   or maybe i didn't understand you question correctly...