Rhys Lewis

Chair W3C Device Independence Working Group

Director of Software Architecture

Volantis Systems Ltd

Metadata and Device Independence

Agenda

The DIWG Model of the Web

Metadata and the DIWG Model of the Web

Finding the Metadata We Need

The DIWG Model of the Web

Web

Adaptation

Selection

Transformation

Generation

Delivery

Context

URI

Delivery

Unit

Application

Content

Adaptation Rules

DU

PU

PU

PU

AU

AU

AU

DU

DU

DU

Distributed Adaptation

Web

Adaptation 1

Selection

Transformation

Generation

Delivery

Context

URI

Delivery

Unit

Application

Content

Adaptation Rules

DU

PU

PU

PU

PU

AU

AU

AU

Adaptation 2

Selection

Transformation

Generation

Adaptation Rules

URI+

DC

DU+

MD

Application

Content

AU

AU

AU

Meta

Data

DU+

MD

DU+

MD

DU

Metadata and the DI Model [1]
Whole Resource Metadata

Metadata that applies to the entire resource

Traditional

HTTP headers and negotiation are an example

Useful but insufficient on its own

Image selection example

Delivery Unit

Image Reference

Adaptation

Image Version A

Image Version B

Image Version C

Metadata for Verson A

Metadata for Verson B

Metadata for Verson C

Metadata and the DI Model [2]
Sub-resource Metadata

Finer granularity metadata

Annotations within a resource

Enhance that ability for authors to make clear their intent

“Semantic Enrichment” of a resource

Presentation markup tends to be very general

Semantics limited to document structure

paragraphs, headings, sections, lists

Styling mechanisms must be very general

Essentially free of semantics

class=”menu” doesn't guarantee its a menu

Allow adaptation to interpret resources more completely

XHTML Version 2 is introducing a mechanism

Finding the Metadata We Need
The Process

Survey

Survey the needs of adaptation

Survey the information available

from devices

from users

Survey the information found useful in annotation

Experiences from people who have done it

Survey the information needed from the resource

Analyse

the gaps in the information available

Define

the new information

the appropriate representations and ontologies

Rhys – history + DIWG and W3C

Simplest view of the model – single step adaptation

Note that the fundamental adaptation operations are selection, transformation and generation.

Note flow of delivery context. DC in this case is associated with device, but doesn't necessarily have to be only that – see next slide

Represents server side adaptation. This is how current systems from telecommunications operators and software vendors work.

Cover terminology

Functional and harmonized user experience. In functional, could use decorating the fire exit as the analogy for applications, like emergency information support, where the function is the important thing not the appearance.

Mention the glossary

Represents multistep adaptation. Some parts of the adaptation distributed. Selection of appropriate version of a media resource, for example.

Note flow of metadata with the DU

Note multistep server side is illustrated

Note that client-side adaptation is hinted at by metadata at the devices. This could be because an assistive technology is making use of this metadata

Note the implications – how much adaptation does a step do? Commit vs. defer.

It is insufficient because it supports only selection between alternative resources. Adaptation is more than this.

It does not necessarily have the appropriate granularity. There is no longer a guarantee of a one-to-one relationship between a page an author creates and the page as experienced by a user. One authored 'page' may turn into many perceivable units on a small device.

It does support situations where adaptation is just selection. Hence the image example.

An adaptation processor is building a delivery unit. It needs to provide a reference to an appropriate version of an image for use by the requesting device. It selects an appropriate representation based on the metadata available. This might include width, height, color depth, encoding etc. In addition, an author might express intent about the destination for these versions, again in terms of metadata. Note that all of these characteristics, including the author's intent, apply to the entire resource. Adaptation is selection in this case.

Ultimately we want the ontologies/vocabularies

We need to know which information is worth adding and how to represent it.

We don't need to add information that is already available. Much image metadata is already available in the resource itself.

As with Delivery Context, we anticipate a core ontology and an extension mechanism.

Metadata and Device Independence

Mark Watson

2001-04-19T18:25:35

Care Of