> I don’t get it. How do I now that something is a data definition and not just more data? In our ScrollSet implementation, a measure definition (what you call

> I don’t get it. How do I now that something is a data definition and not just more data? In our ScrollSet implementation, a measure definition (what you call a "data definition") is a subset of a parser. You will know something is a measure definition when you see a line starting with a word with a "Parser" postfix, and nested inside that definition is a line like "extends abstractMeasureParser". Below is a link to a web IDE we built. You can see all of the measure definitions currently powering PLDB on the left. On the right, you can see a concept ("more data", in your terms). https://jtree.treenotation.org/designer#url%20https%3A%2F%2Fpldb.io%2Fpldb.grammar%0AprogramUrl%20https%3A%2F%2Fpldb.io%2Fconcepts%2Frecfiles.scroll https://jtree.treenotation.org/designer#url%20https%3A%2F%2F... > He calls it a trick, why? The current term of art is "Offi-side rule" (https://en.wikipedia.org/wiki/Off-side_rule https://en.wikipedia.org/wiki/Off-side_rule). I never liked that term. I call it the indentation trick. But I am referring to the Offside_rule.