designated for a specific type of event. For example, music for a piodalan (birthday celebration) is different from music used for a metatah (teeth grinding) ceremony, just as it is for weddings, Ngaben (cremation of the dead ceremony), Melasti (purification ritual) and so forth. The diverse types of gamelan are also specified according to the different types of dance in Bali. According to Walter Spies, the art of dancing is an integral part of Balinese life as well as an endless critical element in a series of ceremonies or for personal interests. Traditionally, displaying female breasts is not considered immodest. Balinese women can often be seen with bared chests; however, a display of the thigh is considered immodest. In modern Bali, these customs are normally not strictly observed, but visitors to Balinese temples are advised to cover their legs. In the Balinese naming system, a person's rank of birth or caste is reflected in the name. Puputan A puputan is an act of mass suicide through frontal assaults in battle and was first noted by the Dutch during the colonization of Bali. The latest act of puputan was during the Indonesian War of Independence, with Lt. Colonel I Gusti Ngurah Rai as the leader in the Battle of Margarana. The airport in Bali is named after him in commemoration. Religion The vast majority of the Balinese believe in Agama Tirta, "holy-water religion". It is a part of Hinduism. Travelling Indian priests are said to have introduced the people to the sacred literature of Hinduism and Buddhism centuries ago. The people accepted it and combined it with their own pre-Hindu mythologies. The Balinese from before the third wave of immigration, known as the Bali Aga, are mostly not followers of Agama Tirta, but retain their own animist traditions. Wet-rice agriculture is a mainstay of Balinese food production. This system of agriculture is extremely water-intensive, and requires a substantial network of irrigation to be effective as a subsistence strategy in Bali. A system of irrigation networks (subak) exists to redistribute access to water in Bali. This network of both underground tunnels (weirs) and canals diverts water from natural water sources into the wet-rice cultivation fields utilized by Balinese farmers to grow their staple crop. The system of cooperative water redistribution is tied to religious and cultural practices among the Balinese, and represents an economic system based on mutual obligation, and managed by