5   <element name="proofSystem">
7       <element name="rule">
8         <attribute name="name"/>  attribute
10 	  <ref name="antecedent"/>
12 	<ref name="consequent"/>
18 <define name="formula">
19   <element name="formula">
21       <ref name="judgement"/>
22       <ref name="expr"/>
27 <define name="consequent">
28   <ref name="judgement"/>
31 <define name="antecedent">
32   <ref name="judgement"/>
35 <define name="judgement">
37     <element name="judgement">
38       <attribute name="name"/>  attribute
40 	<ref name="expr"/>
43     <element name="not">
44       <ref name="judgement"/>
49 <define name="expr">
51     <element name="var">
52       <attribute name="range"/>
54 	<attribute name="index"/>
57 	<attribute name="sub"/>
60     <element name="function">
61       <attribute name="name"/>  attribute
63         <ref name="expr"/>
66     <element name="element">
67       <attribute name="name"/>  attribute
69         <element name="attribute">
70           <attribute name="name"/>  attribute
71           <ref name="expr"/> 
75         <ref name="context"/>
78         <ref name="expr"/>
81     <element name="group">
83         <ref name="expr"/>
86     <element name="string"><text/></element>
90 <define name="context">
91   <element name="context">
92     <ref name="expr"/>