1. A method comprising: in a database system executing on one or more computers, registering different content ID schemas, the registering of the different content ID schemas comprising registering bounding identifiers corresponding to the different content ID schemas; in the database system, registering a set of content identifiers for each of the different content ID schemas, wherein the content identifiers in a content ID schema correspond to content objects identified by the content ID schema, and the content identifiers are obtained based on identifying information derived by a programmed processor from audio or visual content signals obtained from the corresponding content objects; forming a globally unique identifier for each of the content objects identified by the different content ID schemas by combining a bounding identifier of the corresponding content ID schema and the content identifier from the same corresponding content ID schema; for each of the globally unique identifiers, maintaining routing information to a metadata source, the metadata source executing on one or more computers; receiving a first content identifier for a first content object; the first content identifier being from a corresponding first content ID schema from the different content ID schemas, the first content identifier being obtained based on first identifying information derived by a programmed processor from an audio or visual content signal obtained from the first content object; determining a first bounding identifier for the corresponding first content ID schema, the first bounding identifier being separate from the first content identifier; using the determined first bounding identifier in combination with the first content identifier obtained based on the identifying information to form the globally unique identifier for the first content identifier; and routing a user device to the metadata source associated with the globally unique identifier for the first content object using the routing information.