[MathML3-last-call] Clarify how "symmetric" should be set by the Operator Dictionary

[Frédéric WANG]

I like the compact form to list boolean valued properties of an operator
in Appendix C. However, in the section that describes the format of
operator dictionary entries, these rules are given in order to set their
values:

"Boolean valued attributes such as stretchy are specified together in
the final Properties column by listing the attribute name if its value
should be set to true by the dictionary."

and "Any attribute not listed for some entry has its default value,
which is given in parentheses in the table of attributes in Section
3.2.5 Operator, Fence, Separator or Accent <mo>."

If I read this correctly, the "symmetric" property should be set to
"true" when it is present and to its default value when it is not. But
its default value is still "true" according to section 3.2.5.2.1 !

[Neil Soiffer-3]

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Thanks for spotting that.  Upon discussing this, some WG members felt that the default should be symmetric='true' for when someone says to stretch something.  That's true for fences, but for arrows, the main use case is in a mtable and there they should not stretch symmetrically.

The tentative conclusion was that  we should remove the sentence in 3.2.5 and do a better job of finding fences in Unicode and defaulting them to symmetric in Appendix C (even though very few fonts will be able to stretch many of them).  That gets the right behavior and allows us to continue to have a compact form for the table in Appendix C.

While modifying Appendix C, we will try to list more of the arrows as being stretchy (even though most fonts don't support stretching them easily).

Does anyone object to this approach?

Neil Soiffer
Senior Scientist
Design Science, Inc.
www.dessci.com
~ Makers of MathType, MathFlow, MathPlayer, MathDaisy, WebEQ, Equation Editor ~

 

2009/9/28 Frédéric WANG <fred.wang@...>

I like the compact form to list boolean valued properties of an operator in Appendix C. However, in the section that describes the format of operator dictionary entries, these rules are given in order to set their values:

"Boolean valued attributes such as stretchy are specified together in the final Properties column by listing the attribute name if its value should be set to true by the dictionary."

and "Any attribute not listed for some entry has its default value, which is given in parentheses in the table of attributes in Section 3.2.5 Operator, Fence, Separator or Accent <mo>."

If I read this correctly, the "symmetric" property should be set to "true" when it is present and to its default value when it is not. But its default value is still "true" according to section 3.2.5.2.1 !

[Neil Soiffer-3]

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Partially resolved.  The default for symmetric has been changed from "true" to "false"

/w3ccvs/WWW/Math/Group/spec/xml/presentation-markup.xml
new revision: 1.280

The operator dictionary (Appendix C) still needs updating so that more fences are identified and given the "symmetric='true'" setting.  Related to this correction, more arrows should also be identified and marked as stretchy by default.

Neil Soiffer
Senior Scientist
Design Science, Inc.
www.dessci.com
~ Makers of MathType, MathFlow, MathPlayer, MathDaisy, WebEQ, Equation Editor ~

 

2009/9/29 Neil Soiffer <neil.soiffer@...>

Thanks for spotting that.  Upon discussing this, some WG members felt that the default should be symmetric='true' for when someone says to stretch something.  That's true for fences, but for arrows, the main use case is in a mtable and there they should not stretch symmetrically.

The tentative conclusion was that  we should remove the sentence in 3.2.5 and do a better job of finding fences in Unicode and defaulting them to symmetric in Appendix C (even though very few fonts will be able to stretch many of them).  That gets the right behavior and allows us to continue to have a compact form for the table in Appendix C.

While modifying Appendix C, we will try to list more of the arrows as being stretchy (even though most fonts don't support stretching them easily).

Does anyone object to this approach?

Neil Soiffer
Senior Scientist
Design Science, Inc.
www.dessci.com
~ Makers of MathType, MathFlow, MathPlayer, MathDaisy, WebEQ, Equation Editor ~

 

2009/9/28 Frédéric WANG <fred.wang@...>

I like the compact form to list boolean valued properties of an operator in Appendix C. However, in the section that describes the format of operator dictionary entries, these rules are given in order to set their values:

"Boolean valued attributes such as stretchy are specified together in the final Properties column by listing the attribute name if its value should be set to true by the dictionary."

and "Any attribute not listed for some entry has its default value, which is given in parentheses in the table of attributes in Section 3.2.5 Operator, Fence, Separator or Accent <mo>."

If I read this correctly, the "symmetric" property should be set to "true" when it is present and to its default value when it is not. But its default value is still "true" according to section 3.2.5.2.1 !

[Frédéric WANG]

> Partially resolved.  The default for symmetric has been changed from
> "true" to "false"
Yes, default all the boolean properties to false seems a reasonable
thing to do. Thanks for having made this change.
> While modifying Appendix C, we will try to list more of the arrows as
> being stretchy (even though most fonts don't support stretching them
> easily).
>
> Does anyone object to this approach?
This sounds good to me.