Dev: Extending the Messaging Protocol

My conception of representation protocol.

• You need to opt-in for a type of representation independently for each variable,
• You need a fallback if the representation you want is not available.
• You might want several reprentation.

add this field to execution_request rich_user_variable : [list_of_desired_repr_variable]

where each of list_of_desired_repr_variable is a dict with the following :

{
    variable:'variable_name',
    prefered_repr: [list of [list of preferred repr format]]
}

example, I have a variable gaussian that I need :

• as a SVG, if not possible as PNG, otherwise, as JPG.
• also as LaTeX, or if not possible as PlainText

{
    variable:'gaussian',
    prefered_repr: [
                    ['svg','png','jpg'],
		    ['latex','text']
                   ]
}

The response should be a dict whose keys are variable name, and value are dict of representation. representation would be a dict with key being repr type, and value dict of status, error_reason and data.

response : {
  gaussian : {
    'svg' : { 
      status:'error',
      data : null,
      error_reason, 'no svg repr for object'
    },
    'png' : { 
      status:'ok',
      data : '0123456789ABCDEF0123456789ABCDEF....',
      error_reason: null
    },
    'png' : { 
      status:'not_computed',
      data : null,
      error_reason: null
    },
    'latex' : { 
      status:'ok',
      data :'\LaTeX',
      error_reason: null
    },
    'text' : { 
      status:'not_computed',
      data : null,
      error_reason: null
    },
  },
  foo : {
    'text' : { 
      status:'error',
      data : null,
      error_reason: 'object does not exist'
    },
  }
}