I/O operations in deferred remote evaluation

Depending on the time and order of input/output we have different situations. First of all, in a workflow (or in a functional program) we cannot predict strictly the order of I/O operations and when they are scheduled. Due to this we simply assume that the state of external inputs does not change with time. This is why inputs - file and URL inputs, and input() statements - can be performed immediately, i.e. during interpreter phase and before runtime. Similarly, outputs - file and URL outputs, and all print() statements - can be performed as soon as the results are available. The only limitation is the locality of the sources and targets: expensive I/O operations (large data) should be carried out on the resources where they will be processed / have been produced.

There are currently no tests with the I/O operations. There should be some tests.

The following features should be implemented in deferred and remote (workflow) execution.

print(), obj to file and obj to url statements

A database query followed by the actual output operation. All these operations should be non-blocking.

• print(): state-dependent and for interactive use and called always immediately: If the object is not evaluated at the time of call null value is printed. After Jupyter integration print() is not necessary.
• obj to file and obj to url are state-independent should return and wait (non-blocking) until objects are evaluated (checked by database queries) and then executed.

Object from file and Object from url statements

• Object from file and Object from url should be blocking all operations depending on the inputs. These can be implemented as Firetasks / Fireworks parent to the dependent Fireworks / Firetasks.