numass-framework/site/content/docs/shards/meta/hidden_values.md

content_type	title	chapter	ordering	label	version	published
doc_shard	Hidden values	meta	10	hidden_values	1.0	true

Meta structure supports so-called hidden values and nodes. These values and nodes exist in the meta and could be requested either by user or framework, but are not shown by casual listing. These values and nodes are considered system and are not intended to be defined by user in most cases.

Hidden values and nodes names starts with symbol @ like @node. Not all meta-data representations allow this symbol so in could be replaced by escaped sequence _at_ in text format (<_at_node/> in XML).