<?xml version="1.0" encoding="UTF-8"?>
<entity_model xmlns="http://www.entitymodelling.org/ERmodel">
<!-- 6-Nov-2017 element.symbol name identifying in place of element.name -->
	<entity_type>
		<name>element</name>
		<presentation>
			<x>1.0</x>
			<y>0.1</y>
		</presentation>
		<value>
			<name>symbol</name>
			<type>string</type>
			<identifying/>
		</value>
		<value>
			<name>name</name>
			<type>string</type>
		</value>
		<value>
			<name>atomic number</name>
			<type>integer</type>
		</value>
		<value>
			<name>relative atomic mass</name>
			<type>float</type>
		</value>
		<composition>
			<type>allotrope</type>
			<cardinality>OneOrMore</cardinality>
			<identifying/>
		</composition>
		<composition>
			<type>valency</type>
			<cardinality>OneOrMore</cardinality>
			<identifying/>
		</composition>
	</entity_type>
	<group>
		<presentation>
			<below>element</below>
			<y>0.5</y>
		</presentation>
		<entity_type>
			<name>allotrope</name>
			<presentation>
			   <w>2.1</w>
			</presentation>
			<value>
				<name>name</name>
				<type>string</type>
				<identifying/>
			</value>
			<value>
				<name>melting point</name>
				<type>float</type>
				<optional/>
			</value>
			<value>
				<name>boiling point</name>
				<type>float</type>
				<optional/>
			</value>
			<value>
				<name>density</name>
				<type>float</type>
				<optional/>
			</value>
		</entity_type>
		<entity_type>
			<name>valency</name>
			<presentation>
				<rightOf>allotrope</rightOf>
				<w>2.1</w>
			</presentation>
			<value>
				<name>number</name>
				<type>integer</type>
				<identifying/>
			</value>
		</entity_type>
	</group>
</entity_model>