Overview
ISO/IEC 21000-18:2007/Amd 1:2008 is an amendment to the MPEG‑21 Part 18 Digital Item Streaming (DIS) specification that introduces a simple fragmentation rule and ECMAScript-based extensions for user-defined processing. The amendment updates the BBL (BBL elements and schema) to support programmable XPath functions, explicit fragmentation controls, and reassembly attributes to better manage streaming and packetized delivery of digital items.
Key Topics and Requirements
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Simple fragmentation rule
- Adds a new FragmentationType with attribute attributes = {none, id, context} to control whether reassembly metadata is attached to fragments.
- Introduces FragmentAt element/type to declare nodes where new fragments are created; supports attributes such as match, deliveryTime, repeat, and optional id.
- Defines rules for included descendants and hierarchical traversal when splitting content into parent/child fragments.
- Specifies bbl:fragmentRef and bbl:fragmentID attributes (when
id mode is used) and bbl:context (when context mode is used) to link parent and child fragments.
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ECMAScript for DIS (user-defined XPath functions)
- Normative reference to ISO/IEC 16262:2002 (ECMAScript); enables authors to register user-defined XPath functions via a new Function element (FunctionType) that contains ECMAScript code.
- Clause 9 defines ECMAScript extensions for DIS:
- Inclusion of the W3C DOM Level 3 Core bindings with restricted mutation rules (BBL and source document nodes are not modifiable unless stated).
- Global bblInfo object exposing functions such as addr(node), deliveryTime(id), duration(id), and finalDeliveryTime(id).
- A DISError object for DIS-specific runtime exceptions.
- ECMAScript bindings for XPath types and BBL variable types (mapping XML Schema types to ECMAScript objects).
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Schema and element updates
- Updated RegisterType, FunctionType, FragmentationType, and FragmentAtType are provided in the amendment’s schema replacement.
Applications and Who Uses It
- Streaming multimedia platform implementers and MPEG‑21 DIS developers who need deterministic fragmentation and reassembly semantics for large digital items.
- Content packaging authors and BBL authors who require custom XPath-based processing or dynamic fragment generation.
- Media server vendors, CDN and broadcast system integrators implementing packet/fragment delivery and reassembly metadata.
- XML/ECMAScript developers working on MPEG‑21 toolchains that need DOM access and time/delivery helpers exposed via bblInfo.
Related Standards
- ISO/IEC 21000-18:2007 (MPEG‑21 Part 18 - Digital Item Streaming)
- ISO/IEC 16262:2002 (ECMAScript language specification) - normative reference for the amendment
- W3C DOM Level 3 Core (DOM API referenced for ECMAScript bindings)
Keywords: ISO/IEC 21000-18:2007/Amd 1:2008, Digital Item Streaming, MPEG-21, simple fragmentation rule, fragmentation, ECMAScript extensions, XPath functions, BBL, fragmentRef, fragmentID, bbl:context, streaming multimedia.