You can't use expression inside other expression in tapestry. It is always recommended to use separate method in java class for such expressions e.g.:
<tr t:type="Loop" t:source="summarizer.byAssociationConceptSorted" t:value="entry" >
<td>${entryConcept.name}</td>
<td>${entry.value}</td>
</tr>
And in java class:
public Concept getEntryConcept() {
return getPage().getStore().loadConcept(entry.getKey());
}
It is also possible but not recommended to use something like this:
<tr t:type="Loop" t:source="summarizer.byAssociationConceptSorted" t:value="entry" >
<td>${page.store.loadConcept(entry.key).name}</td>
<td>${entry.value}</td>
</tr>