Is the platform outside the owner's window a proprietary part?

Whether the platform outside the building window belongs to the exclusive part depends on the specific situation.

First of all, according to Article 2 of the Supreme People's Court's Interpretation on Several Issues Concerning the Specific Application of Laws in the Trial of Disputes over the Ownership of Buildings, specific spaces such as houses, parking spaces and booths within buildings shall be recognized as proprietary parts as mentioned in Chapter VI of the Property Law if they meet the following conditions: (1) they are structurally independent and can be clearly distinguished; (two) independent use, can be used exclusively; (three) can be registered as a specific owner of the ownership object.

Secondly, if the planning belongs to a specific house, and the balcony of the specific house has been included in the sales contract according to the plan when the construction unit sells it, it shall be deemed as an integral part of the exclusive part mentioned in Chapter VI of the Property Law.

Finally, if the planning does not belong to a specific house, nor does it physically belong to a specific house, then the terrace is not exclusive.

To sum up, whether the platform outside the owner's window is a proprietary part needs to be judged according to the specific situation. If you need more professional legal advice, it is recommended to consult a professional lawyer.