Write support

This is a proposal for adding write-support to LDflex.

It requires three new handles:

• AdditionHandler: binds to add and addAll.
• DeletionHandler: binds to delete and deleteAll.
• UpdateHandler (optional): binds to update and updateAll.

Addition

This requires a straightforward handler that intercepts the add and addAll functions that take one mandatory argument.

Adding a single value:

await user.friends.add('https://rubensworks.solid.community/profile/card#me')

SPARQL:

INSERT DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <https://rubensworks.solid.community/profile/card#me>.
}

Adding the first of multiple values:

await user.friends.add(user.friends.friends)

SPARQL:

INSERT DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows
      <http://example.org/A>.
}

Adding multiple values:

for await (const addedFriend of user.friends.add(user.friends.friends)) {
    console.log(addedFriend)
}

SPARQL:

INSERT DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <http://example.org/A>.
}
INSERT DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <http://example.org/B>.
}
INSERT DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <http://example.org/C>.
}

Adding multiple values in bulk:

await user.friends.addAll(user.friends.friends)

SPARQL:

INSERT DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows
      <http://example.org/A>,
      <http://example.org/B>,
      <http://example.org/C>.
}

Note: We can not trap = via the proxy (set), as this requires a synchronous operation, and you can not play around with return values.

Deletion

This requires a handler that intercepts the delete and deleteAll functions that take one optional argument.

Deleting a single value:

await user.friends.delete('https://rubensworks.solid.community/profile/card#me')

SPARQL:

DELETE DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <https://rubensworks.solid.community/profile/card#me>.
}

Deleting the first of a list of values:

await user.friends.delete(user.friends.friends)

SPARQL:

DELETE DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows
      <http://example.org/A>.
}

(maybe this can be done with a DELETE WHERE?)

Deleting a list of values:

for await (const deletedFriend of user.friends.add(user.friends.friends)) {
    console.log(deletedFriend)
}

SPARQL:

DELETE DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <http://example.org/A>,
}
DELETE DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <http://example.org/B>,
}
DELETE DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows <http://example.org/C>,
}

Deleting a list of values in bulk:

await user.friends.deleteAll(user.friends.friends)

SPARQL:

DELETE DATA
{ 
  <https://rubensworks.solid.community/profile/card#me> foaf:knows
      <http://example.org/A>,
      <http://example.org/B>,
      <http://example.org/C>.
}

Deleting first or all possible values:

await user.friends.delete()
await user.friends.deleteAll()

Internally, this corresponds to await user.friends.delete(user.friends) or await user.friends.deleteAll(user.friends), because SPARQL DELETE does not allow blank nodes or variables

Note: We can not trap the delete operator via the proxy (deleteProperty), as this requires a synchronous operation, and you can not play around with return values.

Update

This corresponds to a delete followed by an insert. This is merely convenience functionality that combines deletion and addition (optimizable with a combined SPARQL query: https://www.w3.org/TR/2013/REC-sparql11-update-20130321/#deleteInsert). This requires a handler for set and setAll that take one mandatory argument.

Updating a single value:

await user.name.set('Ruben')

Translation:

await user.name.delete() # Delete a single value
await user.name.add('Ruben') # Add a single value

Updating the first of multiple value:

await user.name.set(user.friends.name)

Translation:

await user.name.delete()
await user.name.add(user.friends.name)

Updating multiple values:

for await (const newName of user.name.set(user.friends.name)) {
    console.log(newName)
}

SPARQL:

await user.name.deleteAll()
await user.name.add(name0) # add calls are separated by for-await iterations.
await user.name.add(name1)
await user.name.add(name2)
...

Updating multiple values in bulk:

await user.name.setAll(user.friends.name)

SPARQL:

await user.name.deleteAll()
await user.name.addAll(user.friends.name)

[rubensworks]

I’ve written everything down in a separate gist that I will update once we decide new things: https://gist.github.com/rubensworks/1123742b048bd2e82624c713a024dcab

I think we agree on everything already, except for perhaps the syntactical sugar and batching. But those build on top of the previous ones, so I can already go ahead an start implementing those.

[angelo-v]

Ok, I see there is https://github.com/RubenVerborgh/LDflex/issues/10 already 😃