Yes, the structure is always there. The trick with unix pipes is that interpreting the structure is always on the receiving side. I don't care if this is CSV or TSV if all I want is the number of lines. I don't care about concrete representations such as JSON or YAML if all I want is to change one string (like a hardcoded server name) to another (like a variable reference). Can you see that? How about this: why would one need a spec or schema in order to pipe an XML file through gzip?