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RE: Formula alignment

From: Daniel Marques <dani@wiris.com>
Date: Fri, 18 Dec 2015 18:54:28 +0100
Message-ID: <2964808098f29b80bd865757e52386ab@mail.gmail.com>
To: David Carlisle <davidc@nag.co.uk>, www-math@w3.org
Thank you very much David for the response and very fast in answering.  As
always you do!!!

-----Original Message-----
From: David Carlisle [mailto:davidc@nag.co.uk]
Sent: viernes, 18 de diciembre de 2015 18:21
To: www-math@w3.org
Subject: Re: Formula alignment

On 18/12/2015 16:56, Daniel Marques wrote:
> Dear MathML group,
>
> I’m just wandering how to align formulas given a symbol. For example,
>
> __y=x+1
>
> x+1=y
>
> (where the _ are spaces)
>
> Reading the MathML specification, I came up with
>
> <mtable>
>
>    <mtd>
>
>      <mi>y</mi>
>
>      <malignmark/>
>
>      <mo> = </mo>
>
>     <mi>x</mi>
>
>      <mo>+</mo>
>
>      <mn>1</mn>
>
>    </mtd>
>
>   <mtd>
>
>      <mi>x</mi>
>
>      <mo>+</mo>
>
>      <mn>1</mn>
>
>      <malignmark/>
>
>      <mo> = </mo>
>
>      <mi>y</mi>
>
>    </mtd>
>
> </mtable>
>
> Do you think that this is the best way to express that?

Apart from a missing mtr (was optional in mathml 1 but not since) yes
but.....


malignmark is one of the trickier areas of mathml and not supported in all
mathml renderers so if you are targetting a specific system and it works
then fine, otherwise I'd split it as two columns right aligned for the left
hand side and left aligned for the rest. Of course that suffers from the
problem that malignmark was trying to address of breaking up the expression
structure.


>
> Another question is whether the malignmark must appear always inside a
> table (mtable)
as specified yes.

  or can be used also combined with <mspace
> linebreak="newline"/>. For example, is the following a valid alternative?
>
>    <mrow>
>
>      <mi>y</mi>
>
>      <malignmark/>
>
>      <mo> = </mo>
>
>     <mi>x</mi>
>
>      <mo>+</mo>
>
>      <mn>1</mn>
>
>      <mspace linebreak="newline"/>
>
>      <mi>x</mi>
>
>      <mo>+</mo>
>
>      <mn>1</mn>
>
>      <malignmark/>
>
>      <mo> = </mo>
>
>      <mi>y</mi>
>
>    </mrow>
>
> Dani
>

I was going to show that that was invalid but it turns out that it is
invalid according to the prose but the constraint that malignmark only
appears in tables isn't checked by the schema. (In principle it could do but
it would greatly complicate the relax schema as you'd have to carry the fact
that you were inside a table through arbitrary pattern rules.  I suppose the
XSD schema could have had an xpath assertion saying explicitly that all
malignmark are within a table.


David

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Received on Friday, 18 December 2015 17:54:52 UTC

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