The Zthes abstract model for thesaurus representation: changes between versions 0.5 and 1.0

• Added new top-level elements termUpdate, termVocabulary, termCategory, termStatus, termApproval and termSortkey.
• The termNote element is now repeatable, and may carry a disambiguating label. It may additionally carry an indication of a constraint on its value.
• Relations may now carry optional weights.
• The <sourceDb> is slightly abstracted, its Z39.50-specific aspects removed to the profile.
• A ``whole thesaurus'' record may now be included, describing the thesaurus as a whole using Dublin Core elements and a repeatable, label-bearing termNote.