First of all, link to SPARQL for those who doesn't know what it is.
So it would be nice to include it as input for Massviews.
- if user doesn't include ?item variable, error should be showed
- probably SPARQL queries will include ?item variable, but people will want to get pageview data for some specific Wikipedia, so there should be some internal converter from Wikidata item to Wikipedia article
- I would suggest inputting SPARQL query itself, not link to it (as they are pretty long) and because you can't directly get results. You have to use another URL (example in Python)