validation skipped on non-modified subjects

[dpetran]

An ex:Person must have a ex:pet with an ex:tail that is datatype xsd:string:

{"@type"          "sh:NodeShape"
 "id"             "ex:personShape"
 "sh:targetClass" {"@id" "ex:Person"}
 "sh:property"    [{"sh:path" {"@list" [{"id" "ex:pet"}
                                        {"id" "ex:tail"}]}
 "sh:datatype" {"id" "xsd:string"}}]}

And we transact perfectly valid Person:

{"@id" "ex:pet-haver"
 "@type" "ex:Person"
 "ex:name" "Guy"
 "ex:pet" {"@id" "ex:dog"
           "ex:tail" "fluffy"}}

All is good.

But then, we update the pet:

{"@id" "ex:dog" "ex:tail" true}

This doesn't trigger validation at all, because we never touch the subject with the class that triggers this shape.

[dpetran]

I have a general question:

• How do we know which shapes need to be validated when we are processing a transaction?

We can't figure it out by just checking the types of the subjects that we modified, which is what we currently. So maybe we validate every shape? Or every shape that has a sh:path that has a predicate that is in the tx?

Which leads to a second question:

• What do we have to validate after processing a transaction?

We currently start with the s-flakes of a subject that got changed, and then depending on the path and the constraints we may pull in other flakes. But if have to re-validate flakes that haven't changed, because of graph-crawling constraints in other shapes, we need a different way to constrain the scope so we don't have to re-validate the whole db: if we have a million Persons in the db, we don't want to re-validate all of them just because we changed one.