Compare MQA Schema to Data Package Table Schema
I'm also involved in https://datapackage.org/ - this includes a schema language for tabular data. A limited variant of this language also used by Wikimedia, so there is some real-world data to play with. Related issue: #210
I created a Comparison of Data Package Data Resource and MediaWiki Tabular Data. Additional schema languages for tabular include MQA Schema, Avram, and SQL/Schemata. Some spreadsheet software further allows to lock/protect properties of cells to create forms and there is a "data validation" feature but this capabilities are very limited so it's far from a schema.
Sounds very good. It contains constraints that are not available now in MQAF, and there are others that are variants of MQAF properties. It is worth to investigate them more deeply.