A central Registration authority registers the assigned namespace identifiers allocated. Different component types are identified by class IDs (CLSIDs), which are Globally Unique Identifiers (GUIDs). PUIDs can be expressed as Uniform Resource Identifiers using the namespace. Individual Internet host computers use domain names as host identifiers, also called hostnames. They are used to complement the identity information provided by the primary biometric identifiers. Resources are identified using Uniform Resource Identifiers. Approximately sixty formal URN namespace identifiers have been registered. The following list describes the NCBI FASTA defined format for sequence identifiers. ICANN also maintains registries of Internet Protocol identifiers. Words include reserved words and user-defined identifiers. This allowed omitting spaces between tokens for brevity or including spaces within identifiers for clarity. They can be configured to different service set identifiers. It identifies data with Application Identifiers (AI). One exception is the handling of unquoted identifiers like table or column names. They may be configured to different service set identifiers (SSIDs).