1. A computer-readable storage medium, that is not a propagating signal, encoded with computer-executable instructions which, when executed by a processor, perform a method for managing metadata associated with digital media content, the method comprising: identifying a first digital media content source and a second digital media content source; identifying a first protocol usable for communication with the first digital media content source and a second protocol usable for communication with the second digital media content source; using a first pluggable protocol adapter to establish a first communication session with the first digital media content source via the first protocol, to identify a first set of metadata items associated with digital media content distributable via the first digital media content source, the metadata items within the first set of metadata having a first format; receiving the first set of metadata items via the first communication session; using a second pluggable protocol adapter to establish a second communication session with the second digital media content source via the second protocol, to identify a second set of metadata items associated with digital media content distributable via the second digital media content source, the metadata items within the second set of metadata items having a second format different from the first format; receiving the second set of metadata items via the second communication session; transcribing the metadata items within the first set of metadata items and the second set of metadata items in accordance with a common format serving as a universal medium for exchange of information about digital media content from different digital media content sources, the common format comprising an envelope format specifying a first portion, a second portion, and a third portion, the first portion to store descriptive data associated with a particular digital media object and information usable to contact the particular source, said descriptive data being derived from one or more metadata items obtained from a particular digital media content source and encoded in a manner as to be available to a plurality of clients, the second portion to store data in a format specific to one or more digital media content sources that provided the metadata items from which the descriptive data stored in the first portion was derived, and the third portion to identify web services offered on behalf of the one or more digital media content sources that provided the metadata items from which the descriptive data stored in the first portion was derived, the web services usable to obtain additional functionality associated with the particular digital media object; based on filter criteria applied to the descriptive data stored in accordance with the first portion of the common format, identifying a relationship between at least one transcribed metadata item originating from the first set of metadata items and at least one transcribed metadata item originating from the second set of metadata items; based on the identified relationship, including the at least one transcribed metadata item originating from the second set of metadata items in a data set; and providing access to the data set to a client-side electronic device, to provide a personal media experience to a user.