From: Frederic WANG <fwsmail35@aol.com>

Date: Sun, 06 Jan 2008 12:37:55 +0100

Message-ID: <4780BD93.6000303@aol.com>

To: www-math@w3.org

Date: Sun, 06 Jan 2008 12:37:55 +0100

Message-ID: <4780BD93.6000303@aol.com>

To: www-math@w3.org

I believe this is the occasion to study the more general issue of mixing graphics and MathML, otherwise you would have to add new MathML tags for each specific notation. Michael Kohlhase and David Carlisle wrote a W3C note 5 years ago about the graphics in MathML ( see http://www.w3.org/Math/Documents/Notes/graphics.xml ). In the section "Non-Hierarchical Mixing of Formulae and Graphics", they studied a case quite similar to the tie bars, except that they did not think about the label. At the end of the page, they proposed a "SVG in MathML" representation, using the "annotation-xml" tag. I think it would not be too difficult to apply this to the tie bar notation, using for example something like : <math xmlns="http://www.w3.org/1998/Math/MathML"> <semantics> <mrow> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>+</mo> <mo>...</mo> <msub id="starttie"> <mi>x</mi> <mi>i</mi> </msub> <mo>+</mo> <mo>...</mo> <msub> <mi>x</mi> <mi>n</mi> </msub> <mo>=</mo> <msub> <mi>y</mi> <mn>1</mn> </msub> <mo>...</mo> <mo>+</mo> <msub id="endtie"> <mi>y</mi> <mi>i</mi> </msub> <mo>+</mo> <mo>...</mo> <msub> <mi>y</mi> <mi>n</mi> </msub> </mrow> <annotation-xml encoding="image/svg" definitionURL="embellishments"> <svg:connection from="starttie" to="endtie" shape="undertiebar" label="i-th summand" /> </annotation-xml> </semantics> </math> Of course, the structure of the "connection" element should be adapted (and include the foreignObject element) if we want to write the label with MathML. > > Hi all. > > I've been talking to some people using MathML for chemistry lately, and got a question about tie bars, which can't usually be represented in MathML. If I understand correctly, tie bars look like a horizontal bracket (i.e. '[') under an equation, and seem to be primarily used to point to two terms in an equation that are related in some way. I'm not sure of this, but there is also probably a requirement to label the horizontal part of the notation. E.g. > > (x_0 + ... + x_i + ... x_n)^a = (x_0 + ... + x_i + ... x_n)^b > | | > ------------------------------- > ith summand > > I hope this comes out okay as ASCII art. > > However, by their nature, they do not respect the equation nesting structure, and so are tricky in MathML. Something like a <starttie/> ... <endtie/> type construct would be necessary. There might also need to be an id, since presumably one can have several tie bars in an equation, and one would need to match the starts and ends. > > I'm interested in hearing if lack of tie bars in MathML has been an issue for others. > > > --Robert -- Frederic WANG http://www.maths-informatique-jeux.com/international/Received on Sunday, 6 January 2008 11:35:57 GMT

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