(registered 2019-03-07, last updated 2019-03-07)

Type name: application

Subtype name: atsc-held+xml

Required parameters: None.

Optional parameters: None.

Encoding considerations: Binary. Same as for application/xml, except 
   constrained to UTF-8. See IETF 7303, Section 9.1.

Security considerations: This media type inherits the issues common 
   to all XML media types – see RFC 7303 [55] Section 10. This media 
   format is used to describe broadcast and broadband services. This 
   format is highly susceptible to manipulation or spoofing for 
   attacks desiring to mislead a receiver about a session. Both 
   integrity protection and source authentication is recommended to 
   prevent misleading of processors. This type does not employ 
   executable content, but since it is explicitly extensible then 
   executable content could appear in an extension. This media type 
   does not provide any confidentiality protection and instead relies
   on the transport protocol that carries it to provide such 
   security, if needed. This media type also includes URL references 
   which if present must be dereferenced in order to properly 
   interpret the content. This creates additional general security 
   considerations. Decoders should make every effort to validate the 
   origin against other transport signaling.

Interoperability considerations: The published specification 
   describes processing semantics that dictate behavior that must be 
   followed when dealing with, among other things, unrecognized 
   elements and attributes, both in the document's namespace and in 
   other namespaces. Because this is extensible, conformant 
   processors may expect (and enforce) that content received is 
   well-formed XML, but it cannot be guaranteed that the content is 
   valid to a particular DTD or Schema or that the processor will 
   recognize all of the elements and attributes in the document.

Published specification: This media type registration is an integral 
   part of ATSC A/331, “Signaling, Delivery, Synchronization, and 
   Error Protection”, Annex H. The payload is defined in Section 
   7.1.8. This specification and XML schema for the content are 
   available at www.atsc.org/standards (the schema(s) are provided in
   a zip file).

Applications that use this media type: ATSC 3.0 television and 
   Internet encoders, decoders and other facility and consumer 
   equipment.

Additional information:

File extension(s): .held

Person & email address to contact for further information:

Editor, Advanced Television Systems Committee (jwhitaker&atsc.org)

Intended usage: COMMON

Restrictions on usage: None

Author: ATSC.

Change controller: ATSC.