Workflow Engine for PHP 5

Welcome!
A Workflow Engine for PHP 5
or: Graph-Oriented Programming with PHP
Sebastian Bergmann
http://sebastian-bergmann.de/
September 14 th 2007

Who I Am
Sebastian Bergmann
Contributor to the PHP Project since 2000
Creator of PHPUnit
Developer for eZ Systems AS
Author, Consultant, Trainer

Who Are You?
Your Background
PHP 5?
OOP?
eZ Components?
Workflow?

Introduction
Business enterprises need to reduce the cost of doing business and continually develop new services and products.
Enterprise Content Management
helps with storing business-critical content (customer data, documents, etc.) in a central repository and in a unified way.
Workflow Management
provides the methodologies and software that help with organizing the processes that operate on this content inside an organization.

What is Workflow Management?
“The automation of a business process, in whole or parts, where documents, information or tasks are passed from one participant to another to be processed, according to a set of procedural rules” [RA01]

What is Workflow Management?
“Technology supporting the reengineering of business and information processes. It involves: (1) defining workflows, i.e., describing those aspects of a process that are relevant to controlling and coordinating the execution of its tasks [...], and (2) providing for fast (re)design and (re)implementation of the processes as business needs and information systems change” [DG95]

Motivation The workflow of eZ Publish 3

Activity-Based Workflow Mgmt. Who must do what when and how ?

Activity-Based Workflow Mgmt. Who must do what when and how ?
Directed Graph
Nodes represent activity steps
Edges between nodes represent the flow
Control Flow
Data Flow
Nodes can have service objects attached to them

Workflow Patterns
W.M.P. van der Aalst, A.H.M. ter Hofstede, B. Kiepuszewski, and A.P. Barros. Workflow Patterns .
Requirements for Workflow Languages
Vocabulary to compare Workflow Languages

Workflow Patterns
Basic Control Flow Patterns
Sequence, Parallel Split (AND-Split), Synchronization (AND-Join), Exclusive Choice (XOR-Split), Simple Merge (XOR-Join)
Advanded Branching and Synchronization
Multi-Choice (OR-Split), Synchronizing Merge (OR-Join), Multi-Merge, Discriminator
Structure
Arbitrary Cycles, Cancel Case, Implicit Termination

Graph-Oriented Programming
Implementation technique for graph-based execution languages
Strategy for implementing graph execution on top of an object-oriented programming language
Original implementation: JBoss jBPM

Provides the means to structure software around graphs
Adds wait states to object-oriented programming language
Ability to suspend and resume executions

Workflow Virtual Machine
Sérgio Miguel Fernandes, João Cachopo, and António Rito Silva. Supporting Evolution in Workflow Design Languages .
Isolate the core of the Workflow Management System from the Workflow Description Language
No standard Workflow Description Language
Workflow Description Languages change
„Compile“ frontend Workflow Description Language(s) to backend representation

Micro-Workflow Architecture
Dragos A. Manolescu. An Extensible Workflow Architecture with Objects and Patterns .
Object-Oriented
Original implementation in Smalltalk
Component-Oriented
Separation of concerns
Components are exchangeable

Micro-Workflow Architecture
Components
Core
Execution
Process
Synchronization
Persistence
Worklist
Manual Intervention
History
Monitoring
Federated Workflow

ezcWorkflow
Reusable workflow engine component
Part of the eZ Components
Version 1.0 released on July 2 nd 2007
Developed as part of my Diploma Thesis

Interlude: eZ Components
Provide a solid platform for PHP application development
Clean and simple API
Excellent documentation
Keep backward compatibility for longer periods of time
Stable and few regressions
Clean IP, Open Source friendly

Interlude: eZ Components <?php require 'ezc/Base/base.php' ; function __autoload ( $className ) { ezcBase :: autoload ( $className ); }
pear channel-discover components.ez.no
pear install ezc/ezcomponents

ezcWorkflow
Pragmatic approach to describe workflows through objects that encapsulate the workflow patterns
A workflow definition is an object graph than can be
programmatically created using the Workflow Definition API or
loaded from an XML file
and executed via the Workflow Execution API

ezcWorkflow Data Storage Workflow Core Wf Definition API Wf Execution API GUI XML Mail / SOAP / ...

ezcWorkflow
Workflow Definition API
Exposes functionality to create , modify , and delete workflow definitions
Workflow Execution API
Exposes functionality to start , suspend , resume , and stop workflow execution
Exposes functionality to monitor workflow execution

ezcWorkflow $workflow = new ezcWorkflow ( 'Test' ); $input = new ezcWorkflowNodeInput ( array( 'choice' => new ezcWorkflowConditionIsBool ) ); $workflow -> startNode -> addOutNode ( $input ); Example: Defining a workflow

ezcWorkflow $branch = new ezcWorkflowNodeExclusiveChoice ; $branch -> addInNode ( $input ); $branch -> addConditionalOutNode ( new ezcWorkflowConditionVariable ( 'choice' , new ezcWorkflowConditionIsTrue ), new ezcWorkflowNodeAction ( 'PrintTrue' ) ); // ... Example: Defining a workflow

ezcWorkflow $merge = new ezcWorkflowNodeSimpleMerge ; $merge -> addInNode ( $true ) -> addInNode ( $false ) -> addOutNode ( $workflow -> endNode ); Example: Defining a workflow

ezcWorkflow $merge = new ezcWorkflowNodeSimpleMerge ; $merge -> addInNode ( $true ) -> addInNode ( $false ) -> addOutNode ( $workflow -> endNode ); $storage = new ezcWorkflowDefinitionStorageXml ( '/path/to/xml/files' ); $storage -> save ( $workflow ); Example: Saving a workflow to XML

ezcWorkflow <?xml version = "1.0" encoding = "UTF-8" ?> <workflow name = "Test" version = "1" > <node id = "1" type = "Start" > <outNode id = "2" /> </node> <node id = "2" type = "Input" > <variable name = "choice" > <condition type = "IsBool" /> </variable> <outNode id = "3" /> </node> <node id = "3" type = "ExclusiveChoice" > <condition type = "Variable" name = "choice" > <condition type = "IsTrue" /> <outNode id = "4" /> </condition> <condition type = "Variable" name = "choice" > <condition type = "IsFalse" /> <outNode id = "5" /> </condition> </node> <node id = "4" type = "Action" serviceObjectClass = "PrintTrue" > <outNode id = "6" /> </node> <node id = "5" type = "Action" serviceObjectClass = "PrintFalse" > <outNode id = "6" /> </node> <node id = "6" type = "SimpleMerge" > <outNode id = "7" /> </node> <node id = "7" type = "End" /> </workflow> Example: Saving a workflow to XML

ezcWorkflow $merge = new ezcWorkflowNodeSimpleMerge ; $merge -> addInNode ( $true ) -> addInNode ( $false ) -> addOutNode ( $workflow -> endNode ); $storage = new ezcWorkflowDatabaseDefinitionStorage ( ezcDbFactory :: create ( $dsn ) ); $storage -> save ( $workflow ); Example: Saving a workflow to a database

ezcWorkflow $execution = new ezcWorkflowDatabaseExecution ( $db ); $execution -> setWorkflow ( $workflow ); $executionId = $execution -> start (); // ... $execution -> resume ( $executionId , array( 'choice' => true ) ); Example: Executing a workflow

ezcWorkflow $execution = new ezcWorkflowTestExecution ; $execution -> setWorkflow ( $workflow ); $execution -> setInputVariable ( 'choice' , true ); $execution -> start (); Example: Testing a workflow

ezcWorkflow
OXID eSales GmbH is planning to go in production with their first product based on ezcWorkflow this fall
Thomas Nunninger (of OXID eSales GmbH) has developed a persistence backend for Zend_Db
Dave Heath has developed a persistence backend for Doctrine
He is also working on an AJAXy workflow editor
Early Adopters

The End
Thank you for your interest!
These slides will be available shortly on http://sebastian-bergmann.de/talks/.

Bibliography
Sebastian Bergmann. Design and Implementation of a Workflow Engine. Diploma Thesis to obtain the degree of Diplom-Informatiker (Univ.) from the Institute of Computer Science of the University of Bonn, Germany, February 2007.

Bibliography
Rob Allen. Workflow: An Introduction . In: Workflow Handbook, Workflow Management Coalition, 2001.
Dimitrios Georgakopoulos and Mark F. Hornick and Amit P. Sheth. An Overview of Workflow Management: From Process Modeling to Workflow Automation Infrastructure . In: Distributed and Parallel Databases, Volume 3, Number 2, Pages 119-153, 1995.

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Workflow Engine for PHP 5

by Sebastian Bergmann on Sep 14, 2007

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Workflow Engine for PHP 5 — Presentation Transcript