[Rdfapi-php-interest] remove, replace

Problem:
I want the mimic Update and Delete functionality present in SQL. 

For example, imagine an RDFS class that has a multiple cardinality property -
like FOAF:knows. If George knows 10 people and I want to remove 5 of them
based on a search - i would do an RDQL query first and then pass the results
to the remove function called 5 times in a loop. (inefficient, but I am not
aware of another solution)
Removing single statement seems trivial enough.

Update seems to be less friendly. 
If 5 out of  George's 10 friend's phone numbers have all changed this would
be easy if I do the same as above using replace:

foreach (rdqlqueryresult)
{
  replace($friend, FOAF:hasphone, ?anyoldPhoneNumberY, $newphonenumber)
}

The problem is when ?anyoldPhoneNumber is also a multiple cardinality item.
In this case I need to know the the previous result I want to replace. 

foreach (rdqlqueryresult)
{
  replace($friend, FOAF:hasphone, $specificPhoneNumber, $newphonenumber)
}

So this all seems a bit hackish. But generally is this the way I should
proceed to get the update and delete functionality?