Hong Kong Document of Identity for Visa Purposes Hong Kong Document of Identity for Visa Purposes The Hong Kong Special Administrative Region Document of Identity for Visa Purposes () is a biometric travel document issued by the Hong Kong Immigration Department to residents of Hong Kong who are unable to obtain a national passport. It is usually valid for seven years. The majority are issued to citizens of the People's Republic of China who have migrated to Hong Kong on a One-way Permit, have lost their mainland hukou thus are unable to obtain a PRC passport, but have not resided in Hong Kong for the 7 years required
Subdivided interval categories Subdivided interval categories In category theory (mathematics) there exists an important collection of categories denoted formula_1 for natural numbers formula_2. The objects of formula_3 are the integers formula_4, and the morphism set formula_5 for objects formula_6 is empty if formula_7. Subdivided interval categories are very useful in defining simplicial sets. The category whose objects are the subdivided interval categories and whose morphisms are functors is often written formula_8 and is called the simplicial indexing category. A simplicial set is just a contravariant functor formula_9. The category 𝟘 is an empty interval, that is, an empty category, having no objects nor