How invested is the user in your app? If this is an enterprise scenario and your user makes a living using your app he'd probably be willing to expend the time

How invested is the user in your app? If this is an enterprise scenario and your user makes a living using your app he'd probably be willing to expend the time to learn the meaning of your icons, and eventually he will be more productive for having done so. In a consumer app, especially one which the user only uses occasionally the bar is much higher, so your icons should be much more obvious, because the user will just delete your app if he can't figure out your icons.