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OpenACS Workflow

This presentation introduces the OpenACS Workflow package, covering roles, cases, actions, states, and how to define and integrate workflows in web applications.

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OpenACS Workflow

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  1. OpenACS Workflow Mark Aufflick pumptheory.com

  2. This presentation • Goal: Learn to use a workflow in a web application • The OpenACS Workflow package • Roles, Cases, Actions & States • Defining a workflow • Integrating a workflow with your app

  3. A Brief History • The original ACS Workflow package was designed using Petri Nets as the underlying formal model • It’s design was very thorough, but the use of Petri Nets was overcomplicated and unnecessary in perhaps 95% of use cases • In 2003 Lars Pind of Collaboraid didn’t use the existing workflow package because it was cumbersome and unfinished – even though he was the original author while working for ArsDigita!

  4. The new Workflow • An analysis of common use cases showed that all common business workflows can be modeled with a simple Finite State Machine • The new workflow package is a modular development framework, and allows multiple workflow models to be used • Initially only FSMs are supported

  5. User Interface? • Many workflow packages, including the original ACS Workflow, have funky UIs • But – development is nearly always required • So – the new workflow has been designed as a developer framework that allows the power of workflows to be easily incorporated into applications

  6. Workflow Overview • A workflow is a set of: • Roles • Actions • States • plus their relations • A workflow is associated with an object type

  7. Cases • A workflow in action is a CASE • A case revolves around a specific object • A case holds information about: • Current state • Current assignments • Activity log

  8. Roles • From our publishing example, roles might be: • Author • Editor • Publisher • Roles convey permission and responsibility • Roles can be assigned by default and reassigned

  9. Actions • Which actions are available will depend on the current state • Actions may change the state • Actions can have side effects • Allowed roles control who can perform what actions • Assigned roles indicate who is responsible for the action • A workflow has an initial action

  10. States • A workflow has a finite set of states • From our bug tracker example: • Open • Resolved • Closed • A case will always be in exactly one state • States contain almost no information

  11. Defining a workflow • Start by drawing a diagram • -> your states, actions and roles set spec { contract { pretty_name "Contract" package_key "finance-contracts" object_type “finance_contract“ roles { } states { } actions { } } }

  12. Defining a workflow: Roles roles { submitter { pretty_name "Submitter" call_backs { workflow.Role_DefaultAssignees_CreationUser } } assignee { pretty_name “Assignee” callbacks { bug-tracker.ComponentMaintainer bug-tracker.ProjectMaintainer workflow.Role_PickList_CurrentAssignees workflow.Role_AssigneeSubquery_RegisteredUsers } } }

  13. Defining a workflow: States submitted { pretty_name "Submitted“ hide_fields { date_approval date_settlement } } approved { pretty_name "Approved" hide_fields { date_settlement } } declined { pretty_name "Declined" hide_fields { date_settlement } } settled { pretty_name "Settled" } discarded { pretty_name "Discarded" }

  14. Defining a workflow: Actions (1) submit { pretty_name "Submit" pretty_past_tense "Submitted" new_state "submitted" initial_action_p t } comment { pretty_name "Comment" pretty_past_tense "Commented" allowed_roles { submitter } priviliges { read write } always_enabled_p t }

  15. Defining a workflow: Actions (2) decline { pretty_name "Decline" pretty_past_tense "Declined" assigned_role "submitter" assigned_states { submitted } new_state "declined" privileges { write } edit_fields { date_approval } } approve { pretty_name "Approve" pretty_past_tense "Approved" assigned_role "submitter" assigned_states { submitted } new_state "approved" privileges { write } edit_fields { date_approval } }

  16. Integrating With Your App's API • Creating new objects • workflow::case::new • Fetching data • workflow::case::get • Editing objects • workflow::case::action::execute • see packages/bug-tracker/tcl/bug-procs.tcl

  17. Integrating with your App’s UI • Bug Tracker demo… • Use ad_form to build the form fields • Workflow will give you: • Action buttons (workflow::case::get_available_actions) • Role assignment (workflow::case::role::add_assignee_widgets ) • Case log ( workflow::case::get_activity_html ) • See packages/bug-tracker/www/bug.tcl

  18. Integrating with your app’s queries • For complex view-only listings, stats etc. • Join with: • workflow_cases • workflow_fsm_states • And others… • See the bug-tracker index-postgresql.xql for an example

  19. Service Contracts and Callback goodness • What is a callback good for? • Notifications • Other side effects • What is a service contract? • ACS Service contract allows packages to define and register implementation of interfaces • ACS Service contract provides mean to dispatch method calls on an interface implementation. • Interface Discovery is available programmatically • The Service Contract interface specification was inspired by WDSL, the interface specfication for web services.

  20. Package development details • APM TCL callbacks: • after-install (workflow::fsm::new_from_spec) • before-uninstall ( workflow::delete ) • before-upgrade • after-instantiate ( workflow::fsm::clone ) • before-uninstantiate( workflow::delete )

  21. References • All references, slides and materials will be posted on the internet at: http://pumptheory.com/collaboration/open-acs/lectures/ • OpenACS Workflow documentation • http://www.collaboraid.biz/developer/workflow-spec

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