- From: David Carlisle <davidc@nag.co.uk>
- Date: Fri, 27 Jan 2006 23:19:55 GMT
- To: public-cdf@w3.org
Math IG comments on the Last Call CDF documents: WICD Core 1.0 http://www.w3.org/TR/2005/WD-WICD-20051219/ WICD Full 1.0 http://www.w3.org/TR/2005/WD-WICDFull-20051121/ WICD Mobile 1.0 http://www.w3.org/TR/2005/WD-WICDMobile-20051121/ Compound Document by Reference Framework 1.0 http://www.w3.org/TR/2005/WD-CDR-20051219/ Summary ======= The current Framework (and hence the profiles defined based on that framework), do not support features necessary for display of compound document formats such as XHTML+MathML, and which have been available in common desktop browsers for many years. The Math Interest Group urgently request that the Framework (and Core and Full profiles), support the automatic determination of the size and alignment of the rendered referenced (or included) language fragment. Historical background ===================== As you will be aware, MathML has long been a primary example of a W3C Recommendation designed for use in a Compound Document Format, having been first issued as a W3C Recommendation in 1998 within a few months of the XML recommendation. Common desktop browsers have been capable of displaying (X)HTML+MathML documents by reference since the initial recommendations. (Roughly speaking Internet Explorer 4 and Netscape 4 era browsers). The mechanisms for referencing external MathML content differed between MathML systems and browsers (applets, plugins, object tag or embed tag, etc) They also suffered from problems with spacing and alignment although that could be overcome to a certain extent using scripting interfaces to modify alloted size. Similarly common desktop browsers (IE 5.5, IE6, Mozilla/Netscape/Firefox) have been able to display XHTML+MathML "CDI" format markup for 4 years or so. Here the situation is rather better than in the CDR case, standard markup can be used, although differences in browser internal interfaces mean that it is more difficult than one would like to manipulate the resulting DOM from script. Thus it has been apparent for at least 8 years that a recommendation was needed specifying the markup and APIs that should be used to provide cross platform access to this capability and the Math Interest Group was very supportive of the creation of the Compound Documents activity. Unfortunately there appears to be a real danger that the current CDF working drafts are standardising a framework that would not support MathML (or any language with similar requirements) at all. We understand that the current priorities are aimed at the Mobile and other small footprint applications, and that MathML would not be included in the Mobile profile, but it is Essential that the _Framework_ support MathML, and highly desirable that the Desktop profile should similarly support the possibility of MathML (if not actually requiring MathML rendering). While standardised access to DOM scripting and interaction is desirable, the most fundamental requirement is the ability to _display_ the embedded language (MathML in our case). The main requirement here is that there has to be negotiation between the renderer of the host language and renderer of the embedded language as to the screen area and position. The size of a mathematical expression can _not_ be specified in the markup, it must be calculated by the MathML renderer (as the size and alignment depend on properties of the rendering engine, current fonts, lineheights and so on, and thus further depends on the state of the CSS engine). Both the width, and the vertical positioning of the embedded rendering must be calculated, so as to align the baseline of the mathematical expression with the baseline of the surrounding text. In the case of CDI formats, this size negotiation is available in IE (via its activex component interfaces, and in mozilla browsers, where the mathml rendering is added as a native extension) in the older CDR formats using plugin and applet markup, it is possible to use javascript to manage the size negotiation, but again the functionality is there (and has been for many years), what was lacking is any standardised interface. The requirements for such a compound document rendering were outlined in this 1998 submission to the Math Working Group http://www.w3.org/Math/W3CDocs/mathmlrequ.html and for a more modern expression of the requirements, a presentation at the W3C's CDF workshop: http://www.w3.org/2004/04/webapps-cdf-ws/papers/designscience.html The nearest the current documents get to discussing the size of the rendered content is 3.3/1 Rightsizing http://www.w3.org/TR/2005/WD-WICD-20051219/#rightsizing which is unfortunately totally inadequate, it is not possible to put the size of a mathematical expression explicitly into the markup, it depends on so many factors, and in particular it depends on the MathML rendering engine being used, and on user defined CSS stylesheets which may alter the ambient environment such as current font size. The CDR framework document gives an example of a XHTML+MathML document (using inclusion rather than reference) however the example is over simplistic as it uses a displayed equation so doesn't demonstrate the essential ability to be able to render inline equations such as E=mc^2 with the equation forming a natural part of the text stream, using the current text size, and with letters correctly aligned on the baseline of the surrounding text. David Carlisle Co-Chair Math Interest Group Writing on behalf of the Group ________________________________________________________________________ This e-mail has been scanned for all viruses by Star. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ________________________________________________________________________
Received on Saturday, 28 January 2006 01:10:07 UTC