John J. Barton John_Barton@hpl.hp.com
Hewlett Packard Labs
Copyright 2001 Hewlett Packard
To allow digital appliances to interact directly with web services we extend form-fill-in markup semantics to support "sensor data". If the sensor is an image sensor, then the data corresponds to an image and posting a form with the image filled in amounts to image upload. Many other kinds of sensors can be supported and the results of including their output in forms can be more elaborate than storage. Our proposal offers a way to support simple image upload in the general framework of forms that is capable of many additional applications.
Our proposal works within the ongoing development of a new generation of forms
based in XML, the XFORMs work at W3C. We propose a new
xform element entitled "
input" to compliment the existing
output" element in XFORMs.
XFORMs separates the form schema, instance values, and presentation. In the
form schema or model, XFORMs supports a "
There isn't a corresponding solution for the instance values or presentation.
For instance values we propose that binary data be referenced by URI. Here is an example:
<model> <string name="album_id" /> <binary name="photo"> <mediaType>image/jpeg</mediaType> <mediaType>image/png</mediaType> </binary> </model> <instance> <album_id>John's Great Adventure</album_id> <photo href="G122F.jpeg"></photo> </instance>
href attribute is URI for a default value in the form in the
same sense that the text in the
album_id field is a default text
value. The appearance of a URI in the instance does not obligate the user agent
to access the named resource. The resolution rules for the URI are exactly the
same ones that apply to URIs that appear in the presentation markup.
This approach to binary instance data parallels a separate proposal for XFORMs to send XMLP (aka SOAP) messages when the user submits the form. Binary data can be carried with the submitted form using the SOAP Messages with Attachments approach. This approach hyperlinks the XML message carried in one part of a multipart/related MIME message to binary data carried in another part. The hyperlink URI can be absolute and globally unique or relative to the message. By using a URI for the binary data in the instance, all of the issues of mixing binary and XML data are handled by the same proven methods.
To solicit the input of sensor data we use a button form control element with
an action attribute value of "
attribute for this same button form control element will point to the value
in the form that is to be supplied. The mapping of particular sensors to particular
form values is entirely determined by the client. For example, when the form
getLocal button that calls for an image type, a camera XFORMs
user agent software will provide a means for the user to associate a image with
the value that corresponds to the button.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns:xsd="http://www.w3.org/2000/10/XMLSchema" xmlns:xform="http://www.w3.org/2001/02/xforms" xmlns:pxml="http://schemas.xmlsoap.org/soap/envelope/"> <head> <xform xmlns="http://www.w3.org/2000/xforms" id="photo_upload" action="http://myphotoservice.com/addphoto.asp" method="postXMLP"> <model> <string name="album_id" /> <binary name="photo"> <mediaType>image/jpeg</mediaType> <mediaType>image/png</mediaType> </binary> </model> <instance> <pxml:Envelope xmlns:pxml="http://schemas.xmlsoap.org/soap/envelope/"> <pxml:Body> <album_id>John's Great Adventure</album_id> <photo></photo> </pxml:Body> </pxml:Envelope> </instance> </xform> </head> <body> <xform:button action="getLocal" ref="photo_upload/pxml:Envelope/pxml:Body/photo">
</xform:button> <xform:submit xform="photo_upload"> Add to <xform:output ref="photo_upload/pxml:Envelope/pxml:Body/album_id" /> photo album </xform:submit> </body> </html>
 XML Protocol Activity
 XForms - the next generation of Web forms
 XForms 1.0: Data Model
W3C Working Draft, 6 April 2000
 XForms Requirements
W3C Working Draft, 21 August 2000
 SOAP - Simple Object Update Protocol
 SOAP Messages with Attachments
Paul V. Biron and Ashok Malhotra. Candidate Recommendation: XML Schema Part 2: Datatypes. Available at: http://www.w3.org/TR/xmlschema-2. 2000.
Form content types of the HTML 4.0.1 specfication.