Substitution Parameters in CQL

[Matthew Dovey <m.dovey@jisc.ac.uk>]

I felt that there was a nore elegant solution to the forms issue, and I've realised what I'd been vaguely thinking of - allowing substitution parameters in CQL.


Basicallly, the idea is that you can put a placeholder in the CQL query itself whose value is take from a url parameter.

I'm going to use {} to indicate these parameters in my examples, but we may need a better syntax to avoid ambiguity.

So the query

author = {qt1}

would be interpreted as author = whatever the value of the qt1 parameter is.

A form with two input boxes allowing an author and title search would have a hidden field for the query parameter with the value

author = {qt1} and title = {qt2}

A more generic query would be

{qi1} {qr1} {qt1} {qb1} {qi2} {qr2} {qt2}

I have used Tony's convention above but there is no particular need to. I could use

author = {author} and title = {title}

This would clearly only work for forms with a fixed know number of search terms. However since in order to have a form which allowed the user to arbitrarily add search terms would require javascript anyway, this isn't an issue.

The idea needs work to turn this into a robust specification (either a new CQL feature or an extension to CQL) but I wanted feedback as to the approach.

Matthew