FF 17 : Processes A presentation by Robin Upton ( ) ‏ Latest version at Attribution – NonCommercial - ShareAlike V Recommended Pre-requisite: FF8: Messages

Motivation for Processes F2F Services are requested by XML, which is a tree: This presentation explains the F2F process, a structure that complements the independent, hierarchical operation of threads and services. 2 1A 1B 1C They are invoked in a correspondingly hierarchical fashion:

Overview of Processes 1A 1B 1C These Child Threads pass data back to their parent process. /1A /1B /1C The process uses these datastreams to update its data. Users are kept informed according to their preferences.... 2) Processes are created at a particular node, 1) 3) 4)...where they launch child threads.

1) Creating A Process Processes are created by the process-add core service, specifying... These run like normal threads, but passing data back to the process... /1A /1B /1C... the URI. Whoever calls the process is the first user. Other users may connect later.... the child-thread(s).... the block. 1A 1B 1C The child- thread(s) run at this node.

2) Returning Data from Child-threads A process’ child-thread may use the return service to send return messages to its parent process at any time: When a child-thread terminates, its contents are passed back in a term message as usual.... Some XML to return... The parent process handles these messages with an F2F script...

3) Updating the Process Data Processes use a script to process data inputs:... Process users may be informed of changes to the The script runs in its own thread, which is addressed. elements specify where incoming data is received. It can access the process’ block as if it were a datastore named “*”.

4) Informing Users Each user has their own connection record, which is consulted to decide whether to contact them: watch-type watch-specifier Send an update to this User? always unused Yes never unused No on-change * unusedIf the data changes on-change xpath If the result of this Xpath changes on-decrement numerical xpath If the result of this Xpath decreases on-increment numerical xpath If the result of this Xpath increases on-no-change unused If the data is unchanged on-no-change xpath If the result of this Xpath is unchanged To update the user, some of the data, chosen by the user’s specifier (an Xpath expression) is sent to their address. *default

Operation of Processes The following core services are for operation of processes: process-add process-edit process-list process-read process-connect process-disconnect Creating a new process. Modifying a process. Listing all the existing processes. Reading details of a process. Create/edit a process connection. Stop listening to a process. process-signal Pause/restart/delete a process.

Summary Recommended Follow-up: FF18: Messages They contact users & manage a data store. F2F processes aid non-hierarchical communication. They are accessed through core services. 1A 1B 1C