Content packaging and MPEG-21 DID

UKOLN is supported by:

Content packaging and MPEG-21 DID

Andy Powell, UKOLN, University of Bath

[email protected]

JISC Joint Programmes Meeting, July 2005, Cambridge

www.bath.ac.uk

a centre of expertise in digital information management

www.ukoln.ac.uk

JISC Joint Programmes Meeting 2

Contents

• why• how

PPS - I’m not really going to tell you how to use MPEG-21 DID since until 24 hours ago I knew pretty much nothing about it, but many thanks to Jeroen Bekaert and Herbert Van de Sompel of LANL for sharing their presentations and thoughts with me…

PPS - I’m not really going to tell you how to use MPEG-21 DID since until 24 hours ago I knew pretty much nothing about it, but many thanks to Jeroen Bekaert and Herbert Van de Sompel of LANL for sharing their presentations and thoughts with me…

PS - I’m only going to tell you how using MPEG-21 DID.

PS - I’m only going to tell you how using MPEG-21 DID.


Why…

• … do we need packaging standards?• because nothing in life is simple!• applications tend to be built around

aggregate objects of one kind or another– digitised books (multiple parts, i.e. pages)– learning objects (pathway thru multiple objects)

• even objects that look simple (e.g. an eprint in an eprint archive) turn out to be complex

• we need to exchange ‘complex objects’


Packaging standards

• framework for encoding ‘complex objects’– containing multiple objects and/or metadata

– may be nested

• often using XML as the encoding framework

• component objects embedded ‘by value’– XML fragments or Base64 encoding or …

• or passed ‘by reference’– URI

• like all standards, there are plenty to choose from:– METS, IMS-CP, MPEG-21 DID, XFDU (CCSDS)

http://dev.dcc.rl.ac.uk/twiki/bin/view/Main/ContentPackaginghttp://dev.dcc.rl.ac.uk/twiki/bin/view/Main/ContentPackaging

XFDU = XML Formatted Data UnitCCSDS = Consultative Committee for Space Data Systems

XFDU = XML Formatted Data UnitCCSDS = Consultative Committee for Space Data Systems


Example 1 – digitised book

• consider digitised book in a ‘digital library’

• complex object (book) made up of component parts (pages)

• the object and the parts each have one or more chunks of associated metadata

• parts may be embedded (by value) or linked (by reference)

• typical application:‘virtual page turner’

• typical packaging format:METS page

book


Example 2 – learning object

• consider a learning object (whatever that is!)• complex object made up of one or more parts

(other learning objects)– documents, images, videos, interactive objects, audio

files, maps, etc.– each with IEEE LOM metadata– some notion of workflow or sequencing ‘thru’ the parts

• typical application:VLE

• typical packaging format:IMS-CP

PDF document

learning object

video multiple-choice

test


Example 3 - eprint

eprint (work)

PDFmanifestation

PDF(manifestation)

MS-Word(manifestation)

now: expose separate simple objects (metadata only)

future: expose complex objects (metadata and full text)

• eprints in eprint archives typically exposed using OAI-PMH currently

• repositories take different approaches to what they expose in their metadata– work, or manifestations, or both

eprint (work)

PDF Word


Some observations…

• complex objects made up of component parts and metadata– component parts need not be digital objects

• common approach to modelling objects crucial to interoperability

• unfortunately… a common approach to modelling is difficult to achieve– especially on an international scale

• but no ‘best practice’ yet for how to model the complex objects found in eprint archives and institutional repositories


MPEG-21

• ISO standard that defines ‘a normative open framework for multimedia delivery and consumption for use by all the players in the delivery and consumption chain’

• MPEG-21 is modular (17 parts!)– Part 2: DID – representation of digital objects– Part 3: DII – identification of digital objects– Part 4: IPMP – enforcement of rights expressions– Part 5: REL – declaration of rights expressions– Part 7: DIA – transcoding based on contextual

information– Part 10: DIP – association of behaviors– Part 16: BF – binary representation of digital objects

• parts can be (and are) used autonomously


MPEG-21 DID

• ISO/IEC 21000-2: Digital Item Declaration– second edition ISO standard

• representation of Digital Objects– referred to as Digital Items

• 3 sections– abstract model – DID– representation of the Model in XML (DIDL)– W3C XML Schema

• other representation of DID may emerge – ISO/IEC 21000-16: Binary Format– Resource Description Framework (RDF)?


DIDL and digital libraries

• development of MPEG-21 largely driven by the big movie/video content owners and broadcast industries

• little widespread involvement by digital library community

• however, significant involvement of staff at LANL Research Library– input into 2nd edition of the standard– ISO to publish the standard for free on the

ISO Web site


MPEG-21 DID modelcontainer

item

(sub-)item

component

resource (datastream)

instantiated as DIDL/XML document

represents the digital item/object/asset

items (with optional nested sub-items)made up of one or more components, eachof which has one or more datastreams

Descriptor/Statement




metadata and/or identifier


ItemDescriptor/Statement dii:identifier doi:10.1234/5678Component

Descriptor/Statement dcterms:created 2005-02-22Resource @mimeType application/xml

@ref http://example.org/getMeta?id=5678Component

Descriptor/Statement dcterms:created 2005-02-21Resource @mimeType

@ref

ItemDescriptor/Statement dii:identifier doi:10.1234/5678Component

Descriptor/Statement dcterms:created 2005-02-2Resource @mimeType application/xml

@ref http://example.org/getMeta?id=5678Component

Descriptor/Statement dcterms:created 2005-02-21Resource @mimeType application/pdf

@ref http://example.org/getPDF?id=5678

Example – journal article

• consider a ‘journal article’ digital asset comprising a PDF document and an XML metadata record (both by reference)

• the asset is mapped to a DIDL ‘Item’ element as follows…

DIDL elementssecondaryinfo type value


MPEG-21 DIDL strengths

• MPEG-21 DID ‘abstract model’ provides a syntax-independent way of– defining underlying ‘complex object’ model in

use– mapping between complex objects from

different repositories

• combination of DID and MPEG-21 Digital Item Identification (DII) allows for unambiguous global identification of complex objects and their component parts


MPEG-21 DIDL strengths (2)

• DID model (and associated DIDL XML schemas) provide open, extensible framework

• in particular, the Descriptor/Statement mechanism provides a way of attaching arbitrary metadata (secondary information) to the digital object or any of its component parts– checksums and/or signatures– DC description– rights metadata (MPEG-21 REL)– etc.


Final thoughts…

• some danger that discussion about packaging formats is a religious issue (i.e. don’t bring it up in a job interview!)

• the really difficult ‘issues’ are in the way that our complex objects are modelled– applies to all the packaging formats, i.e the problem

is independent of chosen packaging standard

• need widespread agreements about how we model our complex objects in order to achieve interoperability

• need to do that on an international basis


Questions?

Content packaging and MPEG-21 DID

Education

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