Christian Timmerer, Maria Teresa Andrade, Pedro Carvalho, Davide Rogai, and Giovanni Cordara, The Semantics of MPEG-21 Digital Items Revisited, Proceedings of ACM Multimedia 2008 2nd International Workshop on the Many Faces of Multimedia Semantics, Vancouver, Canada, October 27 - November 1, 2008.

1. The Seman)cs of MPEG‐21
Digital Items
Chris&an Timmerer
Klagenfurt University (UNIKLU)  Faculty of Technical Sciences (TEWI)
Department of Informa&on Technology (ITEC)  Mul&media Communica&on (MMC)
h;p://research.)mmerer.com  h;p://blog.)mmerer.com  mailto:chris)an.)mmerer@itec.uni‐klu.ac.at
Co‐authors: Chris)an Timmerer (UNIKLU)  Maria Teresa Andrade, Pedro Carvalho
(INESC)  Davide Rogai (Comm.it)  Giovanni Cordara (TILAB)
ACKNOWLEDGMENTS Part of this work is supported by the European Commission in the context of the AXMEDIS (contract no.
511299) and ENTHRONE (contract no. 038463) projects. Further informa)on is available at h;p://www.axmedis.org and h;p://
www.ist‐enthrone.org respec)vely.

2. Outline
• Introduc)on
• MPEG‐21 Digital Items
• Use Cases and Data Models
• Evalua)on (Criteria) and Discussion
• Conclusions
Main source: MPEG core experiment conducted
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 2

3. (MPEG‐21) Introduc)on
Goal
• … to enable transparent and augmented use of mul)media resources across a wide
range of networks, devices, user preferences, and communi)es, notably for trading
(of bits)
What ? – Digital Items (DIs)
• A Digital Item (DI) is a structured digital object with a standard representa)on,
iden)fica)on, and metadata within the MPEG‐21 framework
• Digital Items are “the content” := (Media) Resources + Metadata + Structure
Who ? – Users
• A User is any en)ty that interacts in the MPEG‐21 environment or makes use of a
Digital Item
• Users will assume rights and responsibili)es according to their interac)on with
other Users
• All par)es that have a requirement within MPEG‐21 to interact are categorized
equally as Users
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 3

4. Introduc)on (cont’d)
Issue
• … possible to represent seman)cally similar (or equal) Digital Items
in different ways
– Structure and syntax elements
 Impact on interoperability within and across applica)on domains
(e.g., automated produc)on, delivery, and consump)on within
heterogeneous environments)
Two types of interoperability inves&gated
• Interop@DI: access/browse media resources and metadata,
process/consume the Digital Item as such
• Interop@DID: processing of the DI’s representa)on (parsing,
valida)on)
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5. e.g., Digital Item Iden)fier
referring to ISBN, ISSN,
e.g., MPEG‐7, Dublin Core, ISAN, ISRC, etc.
MPEG‐21 Digital Items SMPTE, proprietary, etc.
Digital Item Model: abstract
terms and concept in EBNF
Digital Item Declara)on
Language (DIDL): XML
schema – building blocks
 Item
 Component
 Descriptor e.g., MPEG‐7, Dublin Core,
 Resource SMPTE, proprietary, etc.
 Choice/Selec)on
DIDL document aka DID
=> highly flexible !!!
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 5

6. (Industry) Adop)ons
UPnP – DIDL‐Lite
• Container format: UPnP specific (bitrate, resolu)on, etc.) + Dublin
Core
MPEG‐21, Part 4 – IPMPDIDL
• Declara)on of protected Digital Items
MPEG Mul&media Applica&on Formats (MAFs)
• “Profiles” Digital Items: subset of tools
MS Interac&ve Media Manager (IMM)
• Implement DI model using OWL
• Dublin Core + domain specific metadata (IPTC, EXIF, SMPTE) +
custom ontology predicates
• Adopts Digital Item Iden)fica)on
=> very/too flexible framework !!!
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 6

7. Use Case(s)
• CP: ini)al DI (media resource + metadata)
• SP: advanced Digital Item with respect to Service Level
Agreements (addi)onal metadata)
• NP: network connec)vity service with QoS
• CC: requests service (from SP) and consumes it (terminal)
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 7

8. Data Models
UCS 1: AXMEDIS UCS 2: ENTHRONE
• Composite Object • Composed and Final Items
• Basic Object
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 8

9. Evalua)on Criteria
Interop@DID Interop@DI
C.1 Conformance to DI model C.8 Content browsing issues
C.2 Conformance to DIDL C.9 Display metadata
C.3 Ambiguity of data models C.10 Media rendering issues
C.4 DID parsing issues C.11 Decode/Display DI as a
C.5 Supported building blocks whole
C.6 Syntax restric)ons
C.7 Seman)c restric)ons
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 9

10. Evalua)on and Discussion
• Players could somehow handle Digital Items
– Metadata not understood is not displayed (i.e., ignored)
• Choice/Selec)on not adopted
– Mul)ple components instead with addi)onal seman)cs
defined
– Only first component is displayed for first use case
• Digital Item Iden)fica)on a requirement
• Interpreta)on of media resources vs. metadata
– Install media decoders – in necessary – on‐demand
– How about metadata? “Metadata decoder” not defined!
 Use proprietary metadata only internally
• Presenta)on logic not mandated
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 10

11. Conclusions
• Flexibility
– Applica)ons implement only a subset
– Add seman)c restric)ons to simplify DI handling
– Allows the use of proprietary metadata
• Flexibility leads to interoperability issues?
– Does not invalid DID
– Processing may lead to a loss of func)onality
– Never (twice) the same DI (analogous to NTSC’s “never the
same color” or “never twice the same color”)
• Need for addi)onal layer to homogenize the use of
MPEG‐21
– Digital Item Processing (DIP)
– Presenta)on of Structured Informa)on (PSI)
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 11

12. Conclusions (cont’d)
• Digital Item Processing (DIP)
– Sugges)ons of interac)on with the DI
– Embed Digital Item Methods (ECMAScript, Digital Item
Base Opera)ons) which are presented to the User
• Presenta)on of Structured Informa)on (PSI)
– Extension of LASeR to point to certain parts of the DID
for presenta)on purposes
– Actual presenta)on according to LASeR
• Both require extension of MPEG‐21
2008/10/31 Chris)an Timmerer, Klagenfurt University, Austria 12

13. Thank you for your a;en)on
... ques)ons, comments, etc. are welcome …
>> Visit the IT campus Carinthia <<
>> h;p://www.it‐campus.at <<
Ass.‐Prof. Dipl.‐Ing. Dr. Chris)an Timmerer
Klagenfurt University, Department of Informa)on Technology (ITEC)
Universitätsstrasse 65‐67, A‐9020 Klagenfurt, AUSTRIA
chris)an.)mmerer@itec.uni‐klu.ac.at
h;p://research.)mmerer.com/
Tel: +43/463/2700 3621 Fax: +43/463/2700 3699
© Copyright: Chris.an Timmerer
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