This expression fell out of favour a long ago. At first it was used with the ‘if’ expression :

  _if do
    equals :field_value => 'customer', :other_value => 'British Petroleum'
    participant :ref => 'Allister'
  end

but lately, the :test attribute of the ‘if’ expression is used :

  _if :test => '${f:customer} == British Petroleum' do
    participant :ref => 'Allister'
  end

In some cases, the ‘if’ expression vanishes and the :if attribute shared by all expressions is used :

  participant :ref => 'Al', :if => '${f:customer} == British Petroleum'

attributes

The ‘equals’ expression accepts those attributes :

• :value
• :field_value
• :variable_value
• :val
• :field_val
• :variable_val

and

• :other_value
• :other_field_value
• :other_variable_value
• :other_val
• :other_field_val
• :other_variable_val

With a bit of luck, they make sense on their own.