Target release	6.0
Epic
Document status	DRAFT
Document owner	Former user (Deleted)
Designer	Former user (Deleted)
Developers	Former user (Deleted)
QA	Olga Faber (Unlicensed)

Goals

Generalise tile-based pull-processing processing to multi-purpose push-processing workflows, i.e. allow execution of GPF graphs from source(s) to target(s).
Make pull-processing an implementation detail of GPF operators
Account for GPF operators that don’t compute tiles (or don’t even output products? maybe later...)
Allow progress monitoring of whole workflow and individual workflow step execution

Background and strategic fit

A number of GPF operators don't compute target tiles at all: Binning, Mosaicing, Pixel Extraction, Statistics, and many more. In order to trigger their computation, awkward code is usually introduced to trigger the one-time computation of the operator's result. Tile-based pull-processing shall become an implementation detail, a number of operators just implement a new execute() method.

Assumptions

It is assumed it is always possible to bring processing nodes in a unambiguous order ensuring correct processing of outputs in each step.
It is assumed that outputs of an operator are still generated by their initialize() methods, otherwise we introduce incompatibility with existing graphs

Requirements

#	Title	User Story	Importance	Notes
1	`Operator.execute()` method	Write operators by implementing a execute() method that takes a progress monitor and a context object as parameter. The context object is used to access the workflow and its steps and can be used e.g. by a target or intermediate step to determine and set appropriate tile sizes to be used by a ReadOp located at the start of the workflow.	Must have
2	API to run graphs as workflow

User interaction and design

Questions

Below is a list of questions to be addressed as a result of this requirements document:

Question	Outcome
What happens if an operator requires in its "execute"-method the results from another operator's "compute_tile"-method?

Not Doing

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