Introduce

UUID is a concept proposed by the International Organization for Standardization (ISO). The UUID is a 128-bit value that can be calculated using a certain algorithm. For efficiency, common UUids can be shortened to 16 bits. UUID is used to identify an attribute type and is considered a unique identifier across all space and time. In general, you can guarantee that any UUID generated anywhere that this value is truly unique will not have the same value. One benefit of using UUids is that you can create new identifiers for new services. In this way, when a client looks up a service, it only needs to indicate the UUID associated with a certain class of service (or a particular service) in its service lookup request, and if the service provider can match the available service to this UUID, it returns a response.