In the current draft of Device Independence Principles it describes a framework where the URIs used in accessing resources or services are the same regardless of the client side environment, device, etc.  This is expressed as

    DIP-2 (DIP-3 in last draft): Device independent web page identifiers

This is obsolete in the sense of a page view vs. a service view, but more importantly it does not scale adequately.  The scopes of web pages are not sufficiently device independent for device independent page identities to be a cardinal principle on which Device Independence strategies are based.  To get to a framework of principles with enough scalability in which to address device independence, on has to look inside the current practices of page composition to realize that it combines elements that are device independent with those that are not.

To this end I have attached a figure showing a logical representation of a web page as a view into a continuing and connected body of resoure -- information or service resource as it may be. 

In the picture, there is a "payload" or "slice covered in the current page" of information which is extracted from a larger "continuing corpus of information."  This is wrapped in "packaging" which forms a "view-conditioned framing" for the payload.

In many framed websites the main frame is basically payload and the rest is packaging.

The framing identifies the site and provides links to site tools and other off-page resources.  Some links are always there but some have to be added as the scope of the  page in the payload domain is drawn smaller and smaller.

The whole point here is that to accomodate different client side interface capabilities (such as large vs. small screens) and network data rates, the amount of material addressed in one nominal page must be allowed to vary, and the URIs will vary along with this.

One of the devices we are targeting is a wall poster on the order of the one in the Diggles Challenge.

http://lists.w3.org/Archives/Public/w3c-wai-ua/2001JulSep/thread.html#164

This is a resource which in the wall chart medium is one page, but for desktop browsing purposes would not be, nor for browsing by a voice dialog.

So in the overall world of serving device diversity, sectioning the resource infoset at different horizons is one of the degrees of freedom that has to be available to be adjusted.

We in WAI need a device independence strategy that doesn't just handle small devices.  We need a device independence strategy that works for the Advanced Collaborative Environments group in the Global Grid Forum, where the device environments range from a voice dialog or on-off buzzer plus sip and puff device up to powerwalls with at least 100X as many pixels as on the average office desktop, driven with full motion video.

The page boundaries may well be the same over some range of adapatation, but this is a design compromise to be determined later, not set as a boundary condition now.

Al