Capabilities, Metadata and Adaptation Architectures

1
Capabilities, Metadata and Adaptation
Architectures

• T-110.456 Next Generation Cellular Networks
• Immo Heino

2
Content

• Adaptation and delivery context
• Methods for describing capabilities and
  preferences
• Adaptation architectures
• Summary

3
Adaptation and delivery context

• Goals of content negotiation/adaptation best
  efforts to provide
• Device independence
• Personalization
• Elements needed for content negotiation
  /adaptation
• A way to describe attributes of the data source
• A way to describe capabilities preferences of
  data requester
• Naming registration schemes for labeling the
  attribute sets
• Frameworks (protocols algorithms) to exchange
  and process attributes
• Delivery context
• A attribute set that characterizes the
  capabilities of the access mechanism, the
  preferences of the user and other aspects of the
  context into which the content is to be delivered

4
General adaptation model

• Picture source W3C DIWG

5
Some characteristics of delivery context

• User interaction methods
• Presentation and capturing modalities
• User agent capabilities
• Scripting, MIME types capabilities
• Connections
• Networks, protocols, bandwidth, latency
• Location and localization
• Geographic location, proximity, languages, time
• Use environment
• Noise, light
• Level of discourse
• Verbosity, content detail
• Trust
• Privacy and security

6
Approaches to describe delivery context

• WWW Consortium (W3C)
• HTTP headers negotiation
• CSS Media Queries
• CC/PP
• DPF
• SMIL
• Open Mobile Alliance (OMA)
• Wap UAProf
• IETF
• Conneg Media Feature Sets
• SIP
• ISO/IEC
• MPEG21
• Open source
• WURFL

7
HTTP headers negotiation

• Accept headers
• Accept text/html (MIME types)
• Accept-Charset iso-8859-5 (charset accepted)
• Accept-Encoding gzip (preferred reply encoding)
• Accept-Language en, fr0.5 (preferred by user)
• User agent string
• User-Agent Nokia6630/1.0 (2.3.129) SymbianOS/8.0
  Series60/2.6 Profile/MIDP-2.0 Configuration/CLDC-1
  .1
• Server driven negotiation vs. HTTP 1.1 agent
  driven negotiation
• Server determines which alternate to send to a
  user agent as a result of examining the user
  agents request header fields
• Server gives a list of available presentations,
  User Agent is responsible for selecting most
  appropriate content

8
HTTP headers negotiation (cont.)

• Pros
• Already used in practice
• Cons
• User agent string format not standardized
• User agent strings are not officially available
  or maintained ( a list of mobile UA agents
  strings http//www.zytrax.com/tech/web/mobile_id
  s.html)
• Limited capability to describe user preferences
  (no support for dynamic attributes/properties)
• Agent driven negotiation delay (multiple
  request-response round trips)
• Numerous proprietary HTTP headers are already
  used for content negotiation

9
CSS2/CSS3 Media Queries

• HTML4 CSS2 supports media-dependent style
  sheets tailored for different media types
• ltlink rel"stylesheet" type"text/css"
  media"screen" href"sans-serif.css"gt ltlink
  rel"stylesheet" type"text/css" media"print"
  href"serif.css"gt
• _at_media screen font-family sans-serif
• CSS3 Media Queries media type media feature
  expressions to limit the scope of the style
  sheets
• E.g. declares what kind of media types a style
  sheet is suitable for
• ltlink rel"stylesheet" media"screen and (color)"
  href"http//www.example.com/color" /gt
• Several media queries can be combined
• Comma Logical Or, and logical AND, only, not
• Associated style sheets applied (by User Agent)
  when matching is true, otherwise ignored

10
CSS2/CSS3 Media Queries

• Pros
• Compatibility with current XML syntaxes
• Style sheets already supported (?)
• Proposed Media Features (CSS3) extends the
  control of content presentation (related to IETF
  Connegs work)
• Width,height,color,resolution,scan, grid etc..
• Cons
• Coarse CSS2 media types (aural, braille,
  handheld, print,projection, screen,
  tty, tv)
• CSS3 not supported yet with current browsers
  (limited support with Opera 7, Mozilla 1.7, IE
  Exploder ?)
• Support for user preferences / non static
  attributes?
• Work in progress since 2002

11
CC/PP

• W3C's Composite Capability/Preference Profiles is
  a framework
• for defining delivery contexts ( vocabularies
  e.g. attribute sets) by using the Resource
  Description Framework (RDF) CCPPStruct
• allows devices to pass a description of these
  characteristics to Web servers for use in content
  selection/adaptation (CCPPex)
• CC/PPStruct standardize the structure of profile
  information
• In practice CC/PP vocabulary is a structured set
  (components) of (unique) attribute names and
  valid attribute data types (RDF /XML Schema)
• Each vocabularies are uniquely identified by a
  URI
• Additional specification of meaning of attributes
  and attribute values is needed
• CC/PPEx standardize the exchange protocol
• Exchange of CC/PP refence profiles (as a URI) or
  profile diffs (inline XML )
• HTTP extension framework (RFC2274) use was
  recommended but not actually used (nor
  functionally equivalent W-HTTP)
• WSP used instead

12
WAP UAProf

• The Open Mobile Alliances (formerly known as the
  WAP Forum) CC/PP based vocabulary (CC/PP
  application) for describing static
  characteristics of mobile phones
• Hardware Platform e.g., screen size, type of IO
  methods etc.
• Software Platform operating system, supported
  markup languages, supported media codecs etc.
• Network characteristics bearer information
• Browser User Agent
• WAP characteristics WML browsers WAP capability
• Push characteristics
• Virtually all CC/PP capable devices use UAProf
• UAProf defines how to include profile information
  in WSP or HTTP requets

13
Dynamic Properties Framework (DPF)

• Device configuration, user preferences and
  environmental conditions can vary dynamically
• W3C Multimodal Interaction Framework (abstract
  framework)
• Interaction manager the logical component that
  coordinates data and manages execution flow from
  various input and output modality component
  interface objects
• System Environment - component enables the
  interaction manager to find out about and respond
  to changes in device capabilities, user
  preferences and environmental conditions

14
Dynamic Properties Framework (cont.)

• Dynamic Properties Framework provides
• the dynamic access (an DOM based interface) to a
  hierarchy (a tree) of properties representing the
  current device capabilities, device
  configuration, user preferences and environmental
  conditions (related to MIF system environment)
• a mechanism to both query and update persistent
  (static) and transient (dynamic) properties
• Properties raise events to notify changes to
  property values
• Complementary to CC/PP
• Work has just started in 4Q/2004

15
IETF Conneg MFS,BCP

• Media Feature Tags (MFS), RFC 2506, 2533
• allows complex descriptions of capabilities and
  preferences by allowing individual predicates to
  be combined using Boolean expressions in
  MIME-type definitions
• An algorithm and a basic implementation of
  feature set matching is also presented
• Media Feature Tag Registration Procedure (BCP),
  RFC 2506
• Handling of tag namespaces
• IETF General Tree, Global tree (g.org-X.xxx)
• URI tree enables the sharing of media feature
  tags without registration (u.org.xxx)
• Example
• Mime-Version 1.0
• Content-Type multipart/mixed boundary"break"
• Content-features ( (pix-xlt800) (pix-ylt600)
•       (  ( (typetext/html)
  (charsetiso-8859-1)
•             (colorlimited) )
•           ( (typetext/plain)
  (charsetUS-ASCII) )
•           ( (typeimage/gif) (colormapped) )
•           ( (typeimage/jpeg) (colorfull) ) )
  )

16
IETF Conneg MSF,BCP (cont.)

• Pros
• Based on solid principles (predicate calculus)
• Extendable
• Protocol independent
• Non-verbose (vs. XML-style tagging)
• Cons
• Sender oriented approach (provides content media
  information that augments basic MIME content type
  information)
• Not actually used in practice (?)

17
MPEG21, SMIL, SIP etc..

• MPEG-21 Multimedia Framework Digital Item
  Adaptation (DIA)
• Descriptions of the environment (terminal,
  networks, user)
• focus on video, audio and image (requantization,
  wavelet and spatial size reduction etc..)
• SMIL (Synchronous Multimedia Integration
  Language) content control module for runtime
  content choices and optimized content delivery
• priorities for different media objects
• Predefined Test Attributes additional
  test-attributes (system-bitrate,
  system-screen-size, system-screen-depth)
• media objects to be preloaded (as bandwidth
  allows) to improve presentation quality.
• SIP (Session Initiation Protocol) provides a
  mechanism for user agents to negotiate the media
  types they can accept in message bodies
• a user agent can announce the MIME media types it
  supports to another user agent.
• SDPng (Session Description Protocol) for content
  negotiation (proposed IETF RFC in 2001)- related
  to work of IETF Multiparty Multimedia Session
  Control

18
Wireless Universal Resource File (WURFL)

• Standard like UAProf is endorsed by many in
  theory, but not enough in practice, which makes
  it hard to rely on
• infrastructure to set up UAProf profiles ?
• There is no guarantee that the info in UAProf are
  accurate
• the WURFL file contains information regarding
  wireless devices' configurations, capabilities
  and features
• Open-source project and intended for developers
  working with the WAP environment.
• Hundreds of possible properties to describe
  static properties (over 300)
• contains over 1,500 devices
• XML based (human readable, machine interpretable)
• - Current size 2.5 MB
• The WURFL framework includes tools, utilities,
  and libraries to parse and query the XML data
• http//wurfl.sourceforge.net

19
Adaptation architecture models

• Architecture alternatives
• at the destination (client side)
• at the intermediary (proxy)
• at the source (server side)
• Dynamic vs. static adaptation
• Adaptation based on predefined profiles (static
  versioning of the content)
• Adaptation on demand (on the fly)

20
Client side adaptation

• Picture source W3C DIWG

21
Client side adaptation (cont.)

• Benefits
• Has full information on own capabilities, user
  preferences and usage context
• Always has up-to-date information
• Can use information that could not be revealed to
  server (due to privacy issues)
• Is not limited to what has been standardized
• Drawbacks
• Requires terminal processing resources (CPU,
  battery life)
• If dummy origin server, needless traffic
  (especially in mobile networks !)

22
Intermediate (proxy) adaptation

• Picture source W3C DIWG

23
Intermediate (proxy) adaptation

• Benefits
• Moves computation from the client site to the
  proxy
• Complex transformations possible (image video
  transcoding etc..)
• Dedicated services possible (versatility)
• Reduces the volume of data transferred to the
  client
• Drawbacks
• Possible bottleneck
• No control for origin data (legal issues ?) nor
  terminal behavior
• Infrastructure maintenance (profile databases)

24
Server side adaptation

• Picture source W3C DIWG

25
Server side adaptation (cont.)

• Benefits
• Full control to the content (content
  modularization)
• Pre calculated content representations possible
  (static adaptation) as well as dynamic adaptation
• Drawbacks
• Infrastructure maintenance (profile databases)
• Storing content locally usually locks it down
  to a specific adapted form (static adaptation)

26
Summary

• Adaptation/content negotiation is a very complex
  issue
• Moving target terminal devices and the network
  infrastructure
• Variation of media types
• Changing (dynamic) properties of delivery
  context
• No single capability/metadata standard will be
  adequate or dominant
• Due to diversity of standardization bodies ?
• Several overlapping work with metadata in
  progress or ended
• Standards will be only partially supported,
  manufacturer specific extensions etc..?
• Suitable adaptation architecture depends on
  application, media content and required level of
  adaptation

27
References

• Device Independence
• http//www.w3.org/2001/di/
• SMIL Content control
• http//www.w3.org/TR/1999/WD-smil-boston-19991115/
  content.html
• Media Queries
• http//www.w3.org/TR/css3-mediaqueries/
• IETF Conneg
• http//www.imc.org/ietf-medfree/index.html
• MPEG21 DIA
• http//www-vs.informatik.uni-ulm.de/proj/qos/draft
  s/m10996_SDPng0406131704.pdf
• CC/PP
• http//www.w3.org/Mobile/CCPP/
• DPF
• http//www.w3.org/TR/DPF/