[ac] Text for XML "read" case

I haven't integrated this into the document as I believe we need some 
section restructuring, but I want to wait for Anne's changes before 
incorporating them. 

--Brad

3.1 Description of Browser Sandbox for XML "read"

The processing instruction is designed explicitly to enable extending 
the sandbox for access to XML content for "read" access. 

Web browsers strive to make it "safe" to run any application fetched 
from the Internet.  In order to safely run untrusted code, the web 
browser tightly controls which resources the web page is allowed to 
access.  In this way, the browser creates a safe "sandbox" in which the 
application can run.

One of the capabilities that web browsers allow is for one site to 
create a hyperlink to another site.  Similarly, a web browser allows a 
site to display an image from another site.  For instance, an HTML page 
from www.example.com may display an image hosted by www.w3.org.  This 
interaction is considered "safe" because the contents of that image are 
displayed to the user, but are not exposed to example.com.

In order to make the experience safe for the end user, web browsers must 
tightly control access to data.  Web pages or XML documents often 
contain sensitive information such as account balances or personal 
correspondences or corporate financial information.  Consequently, the 
browser must prevent an example.com application from making a request 
from your browser that would allow it to "read" your sensitive information.

Because the web browser can not tell which web pages or XML documents 
contain sensitive information and which do not, the browser sandbox by 
default restricts all "read" requests.  An application in example.com 
can not load or inspect the contents of data from any other document. 

Some browsers make an exception if the "read" request is for data from 
the same host or domain.  For instance, a web page from www.example.com 
could request to read another XML document hosted on documents.example.com.

In HTML browsers, the Javascript function XMLHttpRequest allows this 
type of XML read access.  VoiceXML 2.1 browsers implement this 
functionality with an element named <data/>.

The restriction on XML "read" is very strict.  There are cases where an 
application would like to "read" data from another XML document on the 
internet without these restrictions.   For instance, a car reservation 
web site may want to request your trip itinerary data from an affiliated 
airline reservation website to streamline making your car reservation.  
An online retail store may want to read information from a shipping 
company to give you information on when your order will arrive. 

The access-control header allows an XML data document to declare that it 
is safe for the web browser to allow another site to read this data.  By 
specifying an access control header that "allows" example.com to read, 
that particular XML document is saying "Yes, it is safe to allow an 
example.com application to read this data."

3.2 Definition of XML "read"

XML read request:  A request made by an application to load an XML 
document in a manner that allows the application to inspect the contents 
of that XML document.  Upon inspection of the contents, the application 
can perform any other allowed operation using that data such as 
presenting it to the user, performing calculations or making decisions 
based on that data, copying the data into another data object, and 
submitting it back to its own website.

Received on Wednesday, 17 January 2007 21:05:55 UTC