INTERNET DRAFT EXPIRES APR 1999 INTERNET DRAFT
R. Nelson
12 October 1998
Category: EXPERIMENTAL
HTML REFRESH LANGUAGE (HTMLR/1.0)
<draft-rfced-exp-nelson-00.txt>
Status of This Memo
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Copyright Notice
Copyright (C) Ross Nelson (1998). All Rights Reserved.
Abstract
This document describes HTML REFRESH, an EXPERIMENTAL language
and protocol for refreshing HTML pages and allowing serious
thin-client/server applications via HTTP [RFC2068].
1. Rationale and Scope
HTML forms have changed little in functionality or feature since
the inception of the HTML standard. Whilst HTML forms allow the
submission of form data from visible and hidden fields up to a
server side CGI program (or some derivative thereof), the results
must come back as a complete HTML page, either in the existing
window/frame or in another browser window or frame.
This is particularly tedious as the entire target page needs to
be redrawn, even if only certain data elements have been changed.
This has two very negative affects. Firstly, the bandwidth
requirements are increased as the entire page format must be sent
down to the browser again and not just the "field" data which has
changed. Secondly, the affect of redrawing the entire screen does
not allow the development of user friendly thin-client/server
applications (where the client is the web browser)and currently
leads to user disorientation.
Various browser "add-ins", such as "Java" have been developed
whilst HTML forms have largely been allowed to languish. This is
extremely unfortunate as by far the largest number of transactions
over the Internet occur via HTML forms.
This document specifies a HTML REFRESH language, which permits
the refreshing of the form data elements and images on a HTML
browser page without the redrawing of the entire page. This
allows serious user interfaces to be developed whilst using
less bandwidth to do so.
Future versions of this protocol may include extensions for
refreshing non-form elements of a web page, in-line with DHTML
standards.
2. HTML REFRESH LANGUAGE
The HTMLR language is built using the concepts of the HTML
language and is to be used in web browsers in conjuction
with HTML. Needless to say the main delivery method for
HTMLR is HTTP, with the use of a new mime-type.
2.1 HTTP Added mime-type
The HTTP would allow the following mime-type through to the
browser and the web server and browser would comprehend it.
The mime-type is :
text/htmlr
which would denote the content which followed as a HTML refresh.
A HTML REFRESH aware browser would acknowledge the mime-type
and note not to redraw the target page from scratch but instead
integrate the results with it.
2.2 HTMLR Language
The HTMLR Language uses HTML like syntax to denote the refreshes
that are to be made to a HTML page. The following tags and
attributes are used to specify these refreshes. Each tag is
covered below with accompanying description and example.
It is anticipated that HTMLR response pages would be generated by
existing CGI (or like) capable programming languages, for example
PERL, ASP, COLD FUSION, etc. Such languages should be easily
capable of generating HTMLR and also changing the response
mime-type.
2.3 HTMLR TAGS
2.3.1 HTMLR
Syntax:
<HTMLR> ... </HTMLR>
Description:
The HTMLR tag denotes that the all tags and text until the /HTMLR
tag comprise a refresh of the existing HTML page/frame as
displayed by the browser. This tag is equivalent in import to the
<HTML></HTML> tags. Upon encountering a HTMLR tag, a browser
should not clear the existing HTML display page/frame, but rather
interpret the contents of the HTMLR tag and apply the relevant
processing to the current page.
Valid tags within HTMLR tags are specified in the rest of this
section.
Example:
<HTMLR>
..... refresh tags ....
</HTMLR>
2.3.2 WITHFORM
Syntax:
<WITHFORM NAME="form-name">....</WITHFORM>
Description:
The WITHFORM tag denotes which form the tags within it apply to.
The form-name specified with the NAME parameter must match the
name of an existing form on the currently displayed page. The
browser should treat all tags encountered within the WITHFORM
screen as dealing with the specified form where applicable.
Tags which are affected by the WITHFORM tag are SETINPUT,
SETTEXTAREA,CLEARINPUT,WITHSELECT.
If WITHFORM does not enclose these tags, they are deemed to be
relating to the first form on the current page.
Example:
<HTMLR>
<WITHFORM NAME="Person">
.... refresh tags for person form .....
</WITHFORM>
</HTMLR>
2.3.3 CLEARINPUT
Syntax:
<CLEARINPUT {EMPTY|DEFAULT}>
Description:
The CLEARINPUT tag clears all fields/checkboxes/radiobuttons/
textareas/buttons in the currently targeted form and resets them
to either empty or their default values. The targeted form is the
one specified in the enclosing WITHFORM tag, or in the absence
of this, the first form on the page. This should be processed in
sequence by the browser, thus any subsequent SETINPUT tags would
set the fields away from their default or empty values.
The EMPTY attribute sets the fields to empty whilst the DEFAULT
attribute set the fields to the original default value as
specified in the original HTML page.
Example:
<HTMLR>
<WITHFORM NAME="PERSON">
<CLEARINPUT EMPTY>
</WITHFORM>
<STATUS VALUE="Person Record Added">
</HTMLR>
2.3.4 SETINPUT
Syntax:
<SETINPUT NAME="field-name" VALUE="new-value" {CHECKED|UNCHECKED}
{DISABLED|ENABLED}>
Description:
The SETINPUT tag sets the input-field to the new-value specified
in the VALUE parameter. For radio button and checkbox fields, the
CHECKED/UNCHECKED parameter can be specified to alter the field
appearance. The field-name, specified in the NAME parameter must
match the name of a field (hidden/text/radio/checkbox/button) in
the targeted form on the current page. The targeted form is the
one specified in the enclosing WITHFORM tag, or in the absence
of this, the first form on the page. For radio button fields,
the new-value must also match the existing value of the named
field in the current form.
The HTML 3.0 proposed (but not widely implemented) DISABLED
parameter could also be used in SETINPUT, along with ENABLED to
dynamically enable/disable the input field.
Example:
<HTMLR>
<WITHFORM NAME="Person">
<SETINPUT NAME="Name" VALUE="Fred Jones">
<SETINPUT NAME="Dob" VALUE="26/Jan/1971">
<SETINPUT NAME="Address" VALUE="35 Fred Street, Springfield">
<SETINPUT NAME="Sex" Value="MALE" CHECKED>
</WITHFORM>
</HTMLR>
2.3.5 SETTEXTAREA
Syntax:
<SETTEXTAREA NAME="field-name" {ENABLED|DISABLED}
>new-value</SETTEXTAREA>
Description:
The SETTEXTAREA tag sets the input-field to the new-value
specified before the closing /TEXTAREA tag. The field-name,
specified in the NAME parameter must match the name
of a textarea field in the targeted form on the current page.
The targeted form is the one specified in the enclosing WITHFORM
tag, or in the absence of this, the first form on the page.
The HTML 3.0 proposed (but not implemented) DISABLED parameter
could also be used in SETTEXTAREA, along with ENABLED to
dynamically enable/disable the textarea.
Example:
<HTMLR>
<WITHFORM NAME="Person">
<SETTEXTAREA NAME="Comments">
The comments for this record are these
</SETTEXTAREA>
</WITHFORM>
</HTMLR>
2.3.6 SETFOCUS
Syntax:
<SETFOCUS FORM="form-name" FIELD="field-name">
Description:
The SETFOCUS tag set the input focus the field/textarea/selectlist
/checkbox/radiobutton-set/button with the name specified by the FIELD
parameter. The form the field is in is specified by the FORM
parameter. This tag is not affected by the WITHFORM tag as it
must set a definitive focus for the entire page, regardless of
how many forms are present.
Example:
<HTMLR>
<MSGBOX>You must enter an Name</MSGBOX>
<SETFOCUS FORM="Person" FIELD="Name">
</HTMLR>
2.3.7 WITHSELECT
Syntax:
<WITHSELECT NAME="field-name" {DESELECTALL} {REMOVEALL}
{ENABLED|DISABLED}></WITHSELECT>
Description:
The WITHSELECT tag is used to choose and set a select list
object in the current form. The field-name, specified in the
NAME parameter must match the name of a select list object
in the targeted form on the current page. The targeted form is
the one specified in the enclosing WITHFORM tag, or in the absence
of this, the first form on the page.
The DESELECTALL parameter immediately de-selects all existing
items in the select list. The REMOVEALL parameter immediately
removes all items from the select list.
The HTML 3.0 proposed (but seldom implemented) DISABLED parameter
could also be used in WITHSELECT, along with ENABLED to
dynamically enable/disable the SELECT list.
Example:
<HTMLR>
<WITHSELECT NAME="Continent" CLEARALL ENABLED>
<SETOPTION SELECTED>Asia</A>
</WITHSELECT>
</HTMLR>
2.3.8 SETOPTION
Syntax:
<SETOPTION {ADD|DELETE} SELECTED|DESELECTED
VALUE="return-value">display-value</OPTION>
Description:
The SETOPTION tag is used to add, alter, or delete a select
list item of the current SELECT list object. The current select
list is the select list named by the last WITHSELECT within the
currently targeted form. The SETOPTION tag is invalid outside of a
WITHSELECT. The targeted form is the one specified in the
enclosing WITHFORM tag, or in the absence of this, the first form
on the page.
The ADD/DELETE parameter is used to add and delete items
respectively from the SELECT list. The SELECTED/DESELECTED
parameter is used to select/deselect an item after it has been
created, or if it already exists, to alter it.
Example:
See WITHSELECT tag example
2.3.9 MSGBOX
Syntax:
<MSGBOX {TITLE="title"}>message</MSGBOX>
Description:
The MSGBOX tag displays a centered message box to the user with
message supplied before the </MSGBOX> parameter enclosed in it.
The message box must be modal and have an 'OK' button to allow
the user to proceed. The browser should process the MSGBOX tag
immediately before parsing/processing any more of the HTMLREFRESH.
The optional TITLE parameter specfies a title for the messagebox
window.
The text between MSGBOX and /MSGBOX tags should not contain HTML
formating and browsers may wrap the text as well as obey CRLF
combinations found in the text.
The MSGBOX tag allows for easy server generated intrusive messages
without affecting the browser page display.
Example:
<HTMLR>
<MSGBOX TITLE="Update Successful"
>The Record has been updated.</MSGBOX>
</HTMLR>
2.3.10 STATUS
Syntax:
<STATUS VALUE="status-line-value">
Description:
The STATUS tag is used to place the value specified in the VALUE
parameter into the status line at the bottom of the browser
window.
The STATUS tag allows for another form of easy server generated
intrusive messages without affecting the browser page display.
Example:
<HTMLR>
<STATUS VALUE="Please correct the value in the Age Field.">
<BELL>
</HTMLR>
2.3.11 PRINT and PRINTURL
Syntax:
<PRINT {TO=printer-name} {ORIENT=orientation} {TRAY=traynumber}
{COPIES=copy-count}>....</PRINT>
<PRINTURL {TO=printer-name} {ORIENT=orientation}
{TRAY=traynumber} {COPIES=copy-count} SRC="url">
Description:
The PRINT tag is used to print HTML to the specified printer.
The HTML to print is supplied between the PRINT and /PRINT tags.
The print is sent to the printer specified by the optional TO
parameter. If no TO parameter is specified, a printer dialog
should be displayed for the user to select a target printer
from. Printing should occur in parallel to any other browser
processing. The TO option is of most value in an intranet
environment.
The ORIENT, TRAY and COPIES parameters are all options which
allow control over the printing process. The ORIENT parameter
can be used to specify "landscape" or "portrait" printing. The
TRAY parameter can be used to select a paper source. The COPIES
parameter can be user specify an number of copies to print. All
are optional and are most suited to intranet systems.
The PRINTURL tag functions the same as the PRINT tag in terms of
parameters, except that the content to print is supplied by the
url specified in the SRC parameter. The browser should open the
specified url and print the resultant stream as requested. The
printing method should be dictated by the mime-type returned.
Browsers should aim to support multiple PRINT requests in a
single HTML REFRESH stream.
The HTML allowable between the PRINT and /PRINT tags should be
of the same conformance level as the normal HTML supported by
the browser and print exactly the same as a user activated print
of a normal web page.
Example:
<HTMLR>
<MSGBOX>The person record will now be printed to your
"HP" printer.</MSGBOX>
<PRINT TO="hp01" ORIENT="portrait" TRAY="3" COPIES="1">
<HTML>
<HEAD>
<TITLE>Person Record 123321</TITLE>
</HEAD>
<BODY>
<H2>Person Record 123321</H2>
<B>Name:</B> John Smith<BR>
<B>DoB: </B> 14/Mar/1969<BR>
<B>Address: </B> 14 James St Smithville<BR>
<HR>
</BODY>
</HTML>
</PRINT>
</HTMLR>
2.3.12 BELL
Syntax:
<BELL>
Description:
The BELL tag makes the browser produce an audible or visible bell.
Example:
<HTMLR>
<BELL>
<MSGBOX>The server has detected an error.</MSGBOX>
</HTMLR>
2.3.13 SETIMG
Syntax:
<SETIMG NAME="image-name" SRC="url">
Description:
The SETIMG tag is used to set images to new images based on a new
URL. The "image-name" given in the NAME parameter must match the
name of an image on the current HTML page. The new image is loaded
into the same screen area as specified by the original IMG tag on
the original HTML page.
The browser will place the new image on the page in the same
location as the old image, with the same dimensions to avoid
page resizing.
Example:
<HTMLR>
<SETIMG NAME="EmployeePic" SRC="/images/employee/002012.jpg">
</HTMLR>
3. Operational Constraints and Implications
3.1 Web Servers
Web servers may require configuration to allow the text/htmlr
mime-type to be transmitted from the CGI program.
3.2 Web Browsers
Web browsers will naturally be required to support the protocol
with substantial internal changes. On reciept of a HTML REFRESH
of a given page, the page will not be redrawn but instead the
fields altered as required. The refresh should NOT be placed in
any history or "BACK" button cache as this does not make sense.
3.3 Javascript/VBscript Implications
Javascript/VBscript browser implementations could possibly be
extended to support an "OnRefresh" event in a similar manner
as the existing "OnLoad" event. This event would be triggered
upon receipt and application of a HTML REFRESH to the page.
Appropriate extensions to the HTML BODY tag syntax would need to
be made to support the "OnRefresh".
3.4 CGI Programs
CGI program authors would gain the freedom to write serious
thin-client/server applications with HTML REFRESH. For example,
a HTML page could have buttons to move forward and backward
though records in a database. Upon pressing either button, a
submission would be sent to the appropriate Web Server/CGI
program. It would navigate the the next/previous database row and
return new data for the HTML form fields using a HTML REFRESH.
This refresh would only alter the values in the HTML FORM fields
on the page, thus lessening bandwidth requirents, aiding
usability and removing redundant page redraws.
3.5 Security
HTML REFRESH pages would travel under HTTPS the same as HTML and
therefore enjoy the same security benefits.
4. Acknowledgements
Thanks in particular to Steve Aldred, Nigel Williams and last but
not least Joanna Ladon for encouragement and review.
5. References
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., and T.
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2068,
January 1997.
6. Author's Address
Ross Nelson
Wizard Information Services
15 Barry Drive
TURNER ACT 2612
Australia
EMail: Ross.Nelson@wizardis.com.au
INTERNET DRAFT EXPIRES APR 1999 INTERNET DRAFT