This is a proposal for a new way of selecting math mappings in MkIV. I want
to get input from other math users whether this syntax would take care of all
scenarios or not.

There are five different ranges in mathematics:
- digits (0..9)
- lower case Latin (abc..z)
- upper case Latin (ABC..Z)
- lower case Greek (áâã..æ)
- upper case Greek (ÁÂÃ..Z)

A user may want to control what each range is mapped to. So, I suggest a setup
command

     \setupmathmappings
       [
          digits={style,alternative},
         lclatin={style,alternative},
         uclatin={style,alternative},
         lcgreek={style,alternative},
         ucgreek={style,alternative},
       ]

where the options for style are

   normal, bold

while the options for alternative are

   normal, italic, sans, sansitalic, blackboard, script

This command will the mappings for each range. **NOTE**: All combinations are not valid.

A companion command

     \definemathmappings
       [whatever]
       [....]

can be used to define multiple mappings. These mappings can be used by

     \setupmathmappings[whatever]

(An alternative is that these mappings are activated using \whatever ...)

For example, we can define a command to typeset vectors using

     \definemathmappings
       [vectors]
       [ digits={bold,normal},
        lclatin={bold,normal},
        uclatin={bold,normal},
        lcgreek={bold,normal},
        ucgreek={bold,normal}]

     \def\VEC{\groupedcommand{\setupmathmappings[vector]}{}}

If later, we want to represent vectors as sans serif, we can use


     \definemathmappings
       [vectors]
       [ digits={normal,sans},
        lclatin={normal,sans},
        uclatin={normal,sans},
        lcgreek={normal,sans},
        ucgreek={normal,sans}]

This interface makes it easy to switch math fonts for disiplines that want
different style for different alphabet ranges.

It is relatively easy to implement the above interface. All we need is 
some bookkeeping to set the right attributes. The default math mapping 
commands can be reimplmeneted using \definemappings. Before implementing 
this, I want to ask the opinion of other math users.

Would the above interface take care of different use cases, or is it missing
something?

Finally, I am not too happy with the syntax. There are only a few ConTeXt
commands in which the keys take a pair of values. Another option is to allow all
12 valid options

   normal, italic, sans, sansitalic, blackboard, script,
   bold, bolditlaic, boldsans, boldsansitalic, boldblackboard, boldscript

with the variants sansitalic-italicsans, boldsans-sansbold, etc. as synonmyms.

Which way of specifying the keys do you prefer?

Aditya