Transformation function over joined sources? about rml-core HOT 7 CLOSED

Saved you hours of work there @bjdmeest 😂

from rml-core.

I have the feeling these are two issues:

• joining values of a second source as objects of a first source (which I don't think is currently feasible in RML?)
• executing a function over a join result

Right now

• it is possible to join values across data sources, but without join conditions (see eg https://github.com/RMLio/rml-fno-test-cases/blob/master/RMLFNOTC0009-CSV/mapping.ttl, also brought up by @pmaria at https://kg-construct.slack.com/archives/C01QFSW77QF/p1615717859003600)
• it is possible to nest functions (see eg https://github.com/RMLio/rml-fno-test-cases/blob/master/RMLFNOTC0018-CSV/mapping.ttl), so functions on top of functions, but not functions on top of joins.

For what you want, I think we need both (i) a function with a nested condition (in RML+FnO), and (ii) the ability to describe a join condition that does not return the subject of a triples map, but something else, maybe it returns the iteration from a different logical source that matches the condition, so that we could use a reference formulation to take any data field from that iteration (in RML) --> this is related to kg-construct/mapping-challenges#29

What I did:

• I create new issue to describe the current "it is possible to join values across data sources, but without join conditions" in this spec --> kg-construct/rml-lv#16
• I create new issue to describe the current "it is possible to nest functions" in this spec --> kg-construct/rml-fnml#3
• I create new issue to specify feature request "executing a function over a join result" here (still to be discussed, bc I think that depends on how we handle kg-construct/mapping-challenges#29) --> kg-construct/rml-fnml#4

WDYT?

from rml-core.

Isn't "joining values of a second source as objects of a first source" the same as the mapping challeng "join on literals"? At least, that's how I interpreted the latter.

I agree with the above. I also feel that it would be good to solve that issue in RML first, before deciding on how iterations in "function triples maps" should work. It might save us from making things overly complex.

from rml-core.

Isn't "joining values of a second source as objects of a first source" the same as the mapping challeng "join on literals"? At least, that's how I interpreted the latter.

You're totally right, forgot that was already in there 😅

EDIT: I refined my comment above

from rml-core.

Isn't "joining values of a second source as objects of a first source" the same as the mapping challenge "join on literals"? At least, that's how I interpreted the latter.

Totally agree with this too!

from rml-core.

@bjdmeest as this issue has been split into three new issues, where we are actually discussing all, shall we close this?

from rml-core.

awesome, yes!

from rml-core.