National Monuments Authority (NMA) has drafted a document outlining eight categories for about 160 protected monuments in Delhi:

Category I: Protected Monuments/Archaeological Sites inscribed on the World Heritage Cultural sites list of UNESCO including Arab ki Sarai, Nila Gumbad, Hindu Iron Pillar and Tomb of Afsar-wala.
Category II: Protected Monuments and Archaeological Sites included in the Tentative List by World Heritage Committee – ten monuments including Delhi Gate, Ajmeri Gate, Mutiny Telegraph Memorial, and Tomb of Razia Begum.
Category III: Monuments and Archaeological Sites identified for inclusion in the Tentative List of World Heritage Committee – including Ashokan Pillar, Hauz Khas group of Monuments, Tomb of Ghiyasuddin Tughlaqabad, walls and bastions, gates and cause way including the tomb of Dade Khan.
Category IV: Ticketed Protected Monuments and Archaeological Sites (other than World Heritage Sites) including Tomb of Safdarjung, Tomb of Khan-e-khana Nizamuddin, Tughlukabad Fort.
Category V: Monuments and Sites with adequate flow of visitors identified for charging fee – only one monument listed – Tomb of Najaf Khan.
Category VI: Living Monuments which receive large number of visitors/pilgrims. Subcategory A lists Living Monuments at the time of Notification: Sunehri Masjid near Delhi Fort, Nili Mosque, Ancient Mosque. Subcategory B lists Monuments & Sites where worship, congregation and rituals are practised including Tomb of Amir Khusro, Ghiaspur, Tomb of Nizamuddin Auliya and Mazar of Mirza Ghalib.
Category VII: Other Monuments located in the Urban/Semi Urban limits and in remote villages. Subcategory A has 18 Monuments facing severe urban pressure with heavy constructional activities in close vicinity. Subcategory A has 22 Monuments facing urban pressure but possessing significant green space around them. Subcategory C lists monuments where archaeological excavations were conducted or architectural remains are noticeable in vicinity – Sheesh Mahal.
Category VII: Other Categories as the Authority may deem fit including the Heritage Zones and Archaeological Parks.
Links:
Copy of NMA’s draft: http://www.nma.gov.in/nma/downloads/Categorization%20of%20Delhi%20monuments%2027-6.pdf
All India list of Ancient Monuments and Archaeological Sites and Remains of National Importance: http://asi.nic.in/asi_monu_alphalist.asp
List of World Heritage Sites in India: http://asi.nic.in/asi_monu_whs.asp.