Preserving Process
Hyperlink-Based Workflow
Representation
W. Eliot Kimber, DataChannel, Inc
Knowledge Technologies
March 2001
DataChannel, Inc
Agenda
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The Problem
Workflow Analysis Model
Workflow Document DTDs
Workflow Processing Model
Conclusions
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March 2001
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The Problem
• Dissatisfaction with existing workflow
solutions
• WfMC abstract model just not right
• Feels like people are just not thinking
about the problem in the right way:
– Too simple
– Too complicated
– Too implementation specific
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March 2001
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“Workflow Is An Application of
Hyperlinks”
• I Have been saying for years that
workflow is just behavior applied to
hyperlinks
• Never put this to the test
• Could be totally of full of it
• Finally have the motivation and tools to
put it to the test
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The Question
• Does using hyperlinks to model and
implement workflow actually add value?
• If so, what are the implementation
implications?
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The Approach
• Define abstract data model for
workflows
• Map abstract model to hyperdocumentbased implementation model
• Implement behaviors for links to make
workflows active
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March 2001
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Workflow Analysis Model
• Workflow can be modeled as transition
graph between states
• Two forms of workflow:
– Workflow templates: define abstract
process
– Concrete workflows: bind process to
objects and users
• Concrete workflows generated from
workflow templates
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Abstract Workflow
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Key Concepts
• Workflow aggregates states
• States related to possible next states
• States have precondidtions and
postconditions
• Conditions relate to properties of
information objects, workflows, and
information management systems
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States and Conditions
• Preconditions define rules for entry into
a state
• Postconditions must hold when in state
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Concrete Workflows
• Extends abstract workflows by:
– Binding states to information objects
– Adding concept of “agent”
– State transitions become first-class objects
– Adding promotion action
• InformationObjects are the things
managed through the workflow
• Agents set property values and promote
objects from state to state.
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Concrete Workflow Class
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State Transition Class
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Promotion Action
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Summary of Abstract Models
• Model feels pretty good
• Could be implemented fairly directly as
normal engineering exercise
• Would still need way to persist and
interchange workflow templates
• Would not leverage existing information
management functionality
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March 2001
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Link-Based Implementation
• Have standards for writing down hyperlinks in
XML:
– HyTime
– Xlink
• Have existing link management systems
• Should be able to use generic link
management functions to make “workflow
documents” active
• Should be easier than one-off implementation
of abstract model (maybe)
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March 2001
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Basic Approach
• Use XML documents to define
workflows:
– States are normal elements
– State transitions are hyperlinks
• For workflow templates must:
– Declare information object classes
– Declare relevant properties of information
objects, workflow instances, and
information management systems.
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March 2001
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Approach (Cont.)
• Concrete workflows are separate
documents
• Objects are progressed through
workflow by traversing state transition
links
• Change in workflow state results in new
version of workflow document
• Documents could be literal or “virtual”
(DOM or grove only)
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Workflow Template DTD
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Property Declarations
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State Template
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State Transition
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Workflow Template Refinements
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Workflow Template DTD
Summary
• Workflow template documents define abstract
processes
• Not bound to any implementation
• Can be interchanged
• Can include arbitrary information
• Can serve as primary process documentation
(e.g., ISO 9000 documentation)
• Relatively simple to create
• Purely declarative
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Review: Abstract Hyperlink Model
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Concrete Workflow DTD
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Transition Links
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State Element Type
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Concrete Workflow DTD
Refinements
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Concrete Workflow DTD
Summary
• Here, links are from objects to potential states
• All preconditions and post conditions
provided by workflow template
• ManagedObject elements serve as proxies
for real managed objects
• A concrete workflow document reflects the
state of the workflow at a given point in time
• Still completely declarative
• May be underspecified wrt agents and tasks
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March 2001
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Concrete Workflow Document
Processing Model
• Traversal from managed object to
potential state causes promotion of
object to new state
• If traversal succeeds, a new version of
the workflow document is created
reflecting the movement
• Preconditions checked on traversal start
• Postconditions checked on traversal
completion
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Example: Part 1
• Time T[0] MyCWF.xml, v0:
<?xml version=“1.0”?>
<Workflow>
<State id=“state1”>
<ManagedObject id=“ent1”>entity1</ManagedObject>
</State>
<State id=“state2”/>
<TransitionLink>
<ManagedObjects>ent1</ManagedObjects>
<StartingState>state1</StartingState>
<PotentialState>state2</PotentialState>
</TransitionLink>
</Workflow>
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March 2001
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Example: Part 2
• Time T[1] MyCWF.xml, v1:
<?xml version=“1.0”?>
<Workflow>
<State id=“state1”/>
<State id=“state2”>
<ManagedObject id=“ent1”>entity1</ManagedObject>
</State>
<TransitionLink>
<ManagedObjects></ManagedObjects>
<StartingState>state1</StartingState>
<PotentialState>state2</PotentialState>
</TransitionLink>
</Workflow>
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Making It Active: Activity Policies
• If traversal is promotion, have to hook the
traversal action
• HyTime concept of “activity policies” provide
standardized way to model these hooks
• Activity policies bind actions to nodes and
agents
• The “policy” can be any script or program
component
• Provides a single point of integration
• Requires appropriate link management
infrastructure
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Traversal Actions
• Two relevant traversal actions:
– Traverse from node
– Traverse to node
• Traverse-from policies check preconditions
for target anchor
• Traverse-to policies check post conditions for
target anchor
• Traverse-to policies can also perform actions
that cause post conditions to be true
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Traversal With Policies
Traverse-From Policy
Traverse-To Policy
?
?
Transition Link
ManagedObjects
PotentialState
Managed
Object
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State
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Agents Set Properties
• Agents set the properties checked by
preconditions and post conditions
• Agents may be humans or software
components
• Tasks are represented by actions
agents must perform to set states to
satisfy preconditions or post conditions
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Tasks are Implementation Details
• Tasks and their supporting software are
always system specific
• Will change as information management
system changes and as technology evolves
• Processes may not change over long periods
of time (decades)
• Activity policy approach clearly separates the
abstract workflow from implementation details
• User interfaces may present a task-primary
view of workflow
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March 2001
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Some Interesting Characteristics of
Workflow Documents
• If documents are versioned, maintains
complete historical record of the
process activity
• Workflow documents are system
independent
• Reduces implementation task to a
scripting exercise (given appropriate
infrastructure)
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March 2001
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Conclusions
• Overall model is sound
• Seems to be pretty easy to implement
• Use of documents to model workflows feels
appropriate
• Need more implementation experience to really
prove value
• Need to think more about modeling relationships to
users, groups, and tasks
• Good potential synergy with versioned document
management systems
• It helps to have a sophisticated link management
system handy.
Knowledge Technologies
March 2001
DataChannel, Inc