I am asking so because a lot of Muslims in [Masjid Al Nabawi](http://en.wikipedia.org/wiki/Al-Masjid_an-Nabawi) in Madina face to the grave of Prophet Muhammad (PBUH) say Salam directly to prophet or read some Du'a: 

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> السَّلامُ عَلَیکَ یا رَسول الله
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But some people prevent them to do so (specially several years ago - they are more tolerate now I feel) and say:

* Prophet is passed away and he is no longer alive to hear us or reply our Salam.
* We should only ask Allah. Asking something from prophet is Shirk.
* We should face only towards Qibla. Facing towards the grave of prophet is Haram.

For sure the people who ask prophet something - like their forgiveness - don't think prophet is God or doing something independent of Allah. In fact *they ask him to ask Allah something on behalf of them, because he has more reputation near Allah*.

So is saying Salam to prophet Muhammad, asking him something, or facing towards his grave Shirk or Haram? The answers of both Sunni and Shia brothers/sisters are more than welcome.