Want to create a approval workflow from window phone 7

we are integrating sharepoint 2010 with window phone 7.

we want to create a interface on phone using which we can开发者_开发技巧 create a approval workflow on sharepoint site.

Is there any inbuilt sharepoint web service available??

If not what other options we have....

if we try to create our own web service for this , than what should be the functionality of that web service

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Your question is too broad but, yes, SharePoint has web services.