Production Technology Seminar 2009 - EBU Technical

SOA Benefit Media-Aware Benefit
Loose coupling
of applications
Service
abstraction and
mediation
Workflow
persitence
Transformation
and mediation
Media applications produce/consume both content and metadata (messages). A media application may
have a 1 GB video file that can‟t be understood / handled in a standard SOA SOAP message. A mediaaware
ESB synchronizes the capture and delivery of both between services. We obviously do not want to
move large media gigabytes files through an ESB bus – we have to find a way to synchronise the services
with the content that has to be processed at that time.
A media-aware ESB has the ability to "inspect” the media through it metadata and leverage the appropriate
mediation services with dynamic runtime service selection (i.e., dynamically invoke the most appropriate
service/route for the media) – it knows what has to be done with the media.
A media-aware ESB manages both the transaction flow and the media essence transparently between
services. SOA provides dynamic routing capabilities: the messages are routed through the infrastructure to
the appropriate service - it should as well ensure the delivery of content to the right place, but this requires
an extension.
A media-aware ESB transforms both the message (metadata) and the media essence to meet the
requirements of a service. When a message is routed through the infrastructure, it gets transformed by this
architecture to meet the format of the target service - media content has also to be implicitly converted from
one format to another.
This has to deal with adapters, with the infrastructure requesting, responding appropriately to partner
applications.
In order to realise these benefits, we enhanced our standard Websphere SOA framework with
appropriate Media extensions to achieve a Media Industry SOA Solution Framework - called Media Hub
[11], which links business and content processes to support end-to-end workflows for media and other
enterprises.
The media extension could be considered as 2 conceptual enhancements:
� Media Awareness
� Abstract Service Definitions
'Media awareness' means that the entire components that are relevant in this process (like registry, like
ESB, like services) need to understand what the media is about, what it is, what format, what type it is,
what the size, etc. Therefore, we need some additional information describing the content characteristic
that is provided with the message running through the infrastructure and that is provided in the registry
that identifies and describes the service. To describe the media content we use MPEG-21 19 [12]. It is an
open standard, it is applicable and used by other industries. It provides the capability to describe the
media in XML-like format. It can be used separated from the essence itself, so that we can use this
description in the ESB, in a message format running through the infrastructure – the essence being
moved in a separate one. The MPEG-21 DIDL (Digital Item Declaration Language) structure is used in
this context and it might be very complex [13]+[14]. This structure contains all the information (metadata)
about a media object (essence).
'Abstract Service Definition' (ASD) is about combining same category of services into one class. For
example, we want to deal with a general interface for a transcoder, regardless of the specific
implementation. The benefit is to easily exchange one transcoder with another one without necessarily
touching the workflow. It is just within an adapter which has the abstract interface and beneath the
specific interface. So we focus here on the function, not on the proprietary interfaces, and that help us to
manage the resources. How does it look like? The ASD comprises 2 major components [16]:
� The 1 st is the service class design, which is the specific class (e.g. transcoder / watermark / data
mover…);
� The 2 nd one is is the specific mapping from the class to the specific service provider API.
In term of operation we need an 'Adapter' between the 'Orchestration & Monitoring' and the application
itself [17]. This adapter has the 'Abstract WSDL' (Web Service Description Language) and has the
'Adapter Logic' inside which matches to the entire application at that point.
To recapitulate [18]:
� we started from an ESB with a mediation flow, the message models and the communication
19 MPEG-21 Multimedia Framework (ISO/IEC TR 21000-1)
© EBU 2009 / Production Technology seminar / January 27 - 29, 2009
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