Consider a information model where each record is represented by an immutable tuple. This tuple in this context is called a fact.
Example of a fact:
('john', 'age', 18, true)
In this representation, the subject (or entity) 'john' has a value of '18' associated with the attribute 'age'.
To represent a deletion (or retraction) of information, the fourth element of the tuple can be 'false' to indicate that the corresponding entity's attribute no longer has that value.
As it is common in many domains, attributes can have cardinality of either a single value (one) or multiplicity (> 1, many) is allowed.
The following is an example of a list of facts in the format (E, A, V, added?) explained above; i.e. [entity, attribute, value, true if added else if it was retracted).
const facts = [
['gabriel', 'address', 'baker street, 109', true],
['john', 'address', 'apple street, 10', true],
['john', ''address', 'pine street, 88', true],
['john', 'phone', '234-5678', true],
['john', 'phone', '91234-5555', true],
['john', 'phone', '234-5678', false],
['gabriel', 'phone', '98888-1111', true],
['gabriel', 'phone', '56789-1010', true],
];
You can assume the list is ordered from oldest to newest.
The schema for this domain which defines the cardinality for each attribute is:
const schema = [
['address', 'cardinality', 'one'],
['phone', 'cardinality', 'many']
];
i.e. an entity can have multiple (one-to-many) phones, while 'address' is a one-to-one relationship.
In this example, the following records represent the history of addresses that john already had:
[['john', 'address', 'rua alice, 10', true],
['john', 'address', 'rua bob, 88', true]]
Where the current value is the latest one.
The goal of this programming task is to write a function that returns the "current facts" about these entities. i.e. only the latest information at current time.
The function should receive facts (the historical facts) and schema as arguments.
The expected result for this example is the set (order is not important):
[
['gabriel', 'address', 'baker street, 109', true],
['john', 'address', 'pine street, 88', true],
['john', 'phone', '91234-5555', true],
['gabriel', 'phone', '98888-1111', true],
['gabriel', 'phone', '56789-1010', true]
]
Feel free to write the solution in whichever programming language you feel more comfortable.