1). Electronic Service Guide (ESG) - ESG layers
http://docs.google.com/View?id=ddh56dhg_2316mzsbh87
§ The first layer of the ESG is the data model, which is defined in the form of an eXtensible Markup Language (XML) schema.
§ The second layer of the ESG is the instantiation of the data model of the first layer to describe the services available in a specific DVB-IPDC network. The result of this operation is the creation of a number of fragments.
§ ESG XML Fragment: ESG Fragment of an XML instance which is an instantiation of a datatype
§ The third layer is an optional encoding of the fragments: they can be compressed with either GZIP36 or BiM.37
§ The fourth layer encapsulates the fragments in containers (objects that can be delivered by network protocol); in particular, private data that existed only as links in the previous layers (image files, video extracts) is incorporated into the containers.
§ The fifth and last layer corresponds to the delivery of the containers using the FLUTE protocol.
2). Function between ESG layers
ESG layers in specification covers the description of the data model, the instance, the representation, the encapsulation and the transport:
§ Instantiation: Described by the ESG Instance based on the data model using XML Schema.
§ Fragmentation: Partitioning the ESG Instance into ESG XML Fragments.
§ Encapsulation: Encapsulated ESG XML fragments (ESG metadata) into ESG containers
§ Transport: Transported by FLUTE to enable the optimal delivery of containers as files.
3). ESG data model
§ ESG consists of two essential types of information: user attraction information and acquisition information.
§ User attraction information describes services and their contents while the acquisition information contains information for service acquisition.
§ To define a set of data structures, which can be instantiated to describe available services.
§ The ESG data model is defined based on XML Schema and it is aimed at being consistent across all implementations of a system to ensure interoperability.
4). ESG Instance of the ESG Data Model
§ Instantiation: Described by the ESG Instance based on the data model using XML Schema.
§ is a consistent set of ESG data describing the available IP Datacast services.
§ ESG XML Fragment: ESG Fragment of an XML instance which is an instantiation of a datatype
5). ESG Representation
§ Fragmentation: Partitioning the ESG Instance into ESG XML Fragments.
§ support fragmentation of the ESG Instance into ESG XML Fragments and
§ allow an efficient representation of the ESG XML Fragments which minimizes the size of the metadata delivered to users.
§ The partitioning of the ESG Instance into fragments for transportation is supported to enable separately updating parts of ESG data and for performance optimization
§ ESG Representation: ESG Fragments may be represented in three ways.
- Firstly, ESG Fragments may be uncompressed,
- secondly, ESG Fragments may be compressed with GZIP (RFC 1952), and
- thirdly, ESG Fragments may be compressed with BiM specified in ISO/IEC 15938-1 as adopted by DVB-GBS
6). Encapsulation of ESG Fragments into ESG containers
§ Encapsulation: Encapsulated ESG XML fragments (ESG metadata) into ESG containers
§ ESG container: structure to group ESG data into one transport object for delivery purposes aim at supporting the processing and transmission of ESG information in units of considerable size.
§ The processing of ESG Fragments is supported by providing fragment management information which identifies already received fragments, updated fragments and new fragments.
7). ESG Transport
§ Transport: Transported by FLUTE to enable the optimal delivery of containers as files.
§ Transport is achieved by the use of FLUTE sessions
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