NodeExp composability / partial evaluation / parametrization

[VladimirAlexiev]

These are some vague ruminations on

• How composable are NodeExprs?
• Are they amenable to partial evaluation?
• How parameterizable are they?
• Is there some Combinator or Lambda calculus hidden behind them?

SPIN and Constraint Components do this sort of stuff, but I don't see them in the current draft https://raw.githack.com/w3c/data-shapes/master/shacl12-node-expr/index.html

Use case 1: Composition
(Inspired by @HolgerKnublauch example in #484)
shnex:filterShape filters a nodeset by a constraint. Assume a lot of the time that will be a single sh:property constraint.

• Will it be possible to define a custom shortcut like
  ex:filterProperty [...] that expands to shnex:filterShape [sh:property [ ... ]]

Use case 2: Parametrization
(Inspired by https://raw.githack.com/w3c/data-shapes/master/shacl12-node-expr/index.html#EstonianCompanyShapeExample)

• How to parameterize a generic shape "Organization in Country" with <type>, <country>
• How to evaluate it partially (substitute the params) to derive "Company in Estonia" and "University in Bulgaria" shapes?

[afs]

#452 (comment)

[HolgerKnublauch]

@VladimirAlexiev I had just created #498 for this yesterday. Maybe copy your comments there and close this one as duplicate?