"The current version of this document is primarily intended to support linear (broadcast) TV services@ including Pay-Per-View (PPV) services@ and ancillary services such as Emergency Alert Services and EPG services. The following aspects of metadata elements are specified in this document: ? XML schema definitions for the required metadata elements. ? Identification of interfaces across which the metadata elements are exchanged. ? Specifications of mechanisms for such metadata exchanges. It is expected that a future version will support a wider range of services@ such as: ? Video-on-Demand (VoD). ? Video Content Downloads (including ""push VoD""). ? Music/Audio (broadcast@ PPV@ on-demand@ and downloads). Purpose ATIS Standard ATIS-0800017@ Network Attachment and Initialization of Devices and Client Discovery of IPTV Services [8]@ specifies the processes for network attachment of IPTV Delivery Network Gateway (DNG) devices and IPTV Terminal Function (ITF) devices@ and the processes for Service Provider discovery@ Service Provider attachment@ and Services discovery. The present document complements ATIS-0800017 by specifying the data structures (metadata) and transactions that are necessary to implement these processes. The information obtained during the process of Services discovery is often called System Information or Service Information (SI). It provides the basic information needed to acquire IPTV content. This information may be used in conjunction with old fashioned up/down ""channel surfing@"" channel selection by channel number@ or diverse types of Electronic Program Guide (EPG)-based channel navigators."