Not quite, however it is possible to process orders that have been placed through WSI. For example, if the site is configured in AUTH only mode, WSI can be used to Capture the order by just passing the order number and Capture as the action in the OrderManagement node, but completing an entire order from start to finish (eg. adding an item(s) to the cart, filling in customer information (addresses, name/number), completing the order, capturing the order, then sending out notifications is not supported. Each of these (aside from adding items to the cart and placing the actual order) can be accomplished through separate WSI statements
<a href="http://www.aspdotnetstorefront.com">Shopping Cart Software</a>