Clarifying sheduler section.

[fjtirado]

Workflow scheduler is currently described here and here
I have some questions:

1. Should we assume that all workflows can be manually instantiated, not matter its (optional) scheduler definition? I guess the answer is yes, but for completeness I have to raise the question
2. Should we define incompatibilities between the existing options (after, every, cron and on)?. For example, it appears to me that you can schedule every certain time or after certain time, but not both within the same workflow definition. And, although every and cron (depending on the cron expression) can theoretically live together, I have doubts we should allow that combination too.
3. After specify a delay that should be obeyed after a workflow instance ends, but:

• what instantiates this first instance? wait for manual/event/cron instantiation or automatic invocation after the workflow definition file is parsed?
• After means after every workflow instance? So, for example, if we manually/on/cron instantiate three workflows, then there will be another three workflow instances being executed after a certain delay when these three ones are finished?. Or after is just similar to every and just means that just one instance should always be running after certain delay (with the difference that every counts from the moment the workflow start, so there can be in theory more than one instance if the delay is short, and after counts from the moment the workflow ends and it means there will be a max of one instance running at a given moment of time, not matter how short is the delay)?

4. If every is present, the first workflow instance of the period should be started once the workflow is parser or after the given delay?