Implementing Distributed Workflow Systems from XML Specifications

1
ImplementingDistributed Workflow Systems from
XML Specifications
Vineet Kakani Dept of Computer Science University
of Minnesota http//www.cs.umn.edu/Ajanta
2
Project Goals

• Specification of a generic workflow
• Construction of workflow from high level
  specifications
• Rapid construction of any workflow

3
Project Contributions

• Use of XML for specifying the workflow entities
• Design and Implementation of a generic
  distributed collaboration facility built using
  agents

4
Publications

• Distributed Collaborations using Network Mobile
  Agents
• To appear in ASA/MA 2000
• By Anand R Tripathi, Tanvir Ahmed, Vineet Kakani
  and Shremattie Jaman
• Implementing Distributed Workflow Systems from
  XML Specifications
• Submitted to CSCW 2000
• By Anand R Tripathi, Tanvir Ahmed, Vineet Kakani
  and Shremattie Jaman

5
Approach Overview

• Devising a XML schema
• Description of a Workflow Plan
• Shared Objects
• Roles
• Privileges
• Coordination Operations
• Interfacing plan with generic coordination
  facility

6

Steps in building distributed Workflow
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Outline of Presentation

• Workflow
• definition
• examples
• XML schema and example of Workflow Plan using an
  authoring system
• Design of an agent based middleware
• Conclusions and Future work

8
Workflow

• What is workflow ?
• Examples
• Document Workflow
• Internet Based Workflow

9
Document Workflow
10
Internet based Workflow
11
Workflow Models

• Short Term Workflow
• Example - Online Shopping
• Medium Term Workflow
• Example - Project Proposal
• Long Term Workflow
• Example - House Loan

12
Example Authoring System
13
XML Plan

• ltPLANgt
• ltROLE ROLE_ID"docauthor"
• ROLE_NAME"author"
• OBJECT_REF"doc"
• ROLE_INTERFACE"ajanta.UserInterface"gt
• ltPRINCIPAL URN"URNansA"/gt
• lt/ROLEgt
• ltROLE ROLE_ID"docreviewer"
• ROLE_NAME"reviewer"
• OBJECT_REF"doc"
• ROLE_INTERFACE"ajanta.UserInterface"gt
• ltPRINCIPAL URN"URNansB"/gt
• ltPRINCIPAL URN"URNansC"/gt
• lt/ROLEgt
• .........
• lt/PLANgt

XML Specification for Workflow Plan and Role
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XML Object

• ltOBJECT OBJ_ID"doc"
• OBJ_NAME"Document"
• OBJ_TYPE"multipart/alternative"gt
• ltACL/gt
• ltSTATUS/gt
• ltOBJECT OBJ_ID"docch1"
• OBJ_NAME"Chapter1"
• OBJ_TYPE"multipart/alternative"gt
• ltACL/gt
• ltSTATUS/gt
• ltOBJECT OBJ_ID"docch1content"
• OBJ_NAME"Contents"
• OBJ_TYPE"text/plain"gt
• ....
• lt/OBJECTgt

XML Specification for an Object
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XML Access Control

• ltACLgt
• ltACL_ENTRYgt
• ltGROUP ROLE_REF"docauthor"/gt
• ltPERMISSION NAME"read"/gt
• ltPERMISSION NAME"update"/gt
• lt/ACL_ENTRYgt
• ltACL_ENTRYgt
• ltGROUP ROLE_REF"docreviewer"/gt
• ltPERMISSION NAME"read"/gt
• lt/ACL_ENTRYgt
• ltACL_ENTRY TYPE"negative"gt
• ltPRINCIPAL URN"URNansC"/gt
• ltPERMISSION NAME"read"/gt
• lt/ACL_ENTRYgt
• lt/ACLgt

XML Specification for Role Based Access Control
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XML Operation

• ltOPERATION OP_ID "docch1conpublish"
• OBJECT_REF"docch1content"
• OPERATION_NAME"Content_Publish"gt
• ltACLgt
• ltACL_ENTRYgt
• ltGROUP ROLE_REF"docauthor"/gt
  
• ltPERMISSION/gt
• lt/ACL_ENTRYgt
• lt/ACLgt
• ltCLONE_OBJECTgt
• ltTARGET ROLE_REF"docreviewer"/gt
• lt/CLONE_OBJECTgt
• lt/OPERATIONgt

XML Specification for an Operation
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XML Agent Action

• ltOPERATION OP_ID"docstatus"
• OBJECT_REF"status"
• OPERATION_NAME"UpdateStatus"gt
• ltACL/gt
• ltAGENT_ACTIONgt
• ltTARGET ROLE_REF"docreviewer"/gt
• ltREMOTE_METHOD
• OBJECT_REF"status"
  
• METHOD_NAME"updateOp"/
  gt
• lt/AGENT_ACTIONgt
• lt/OPERATIONgt

XML Specification for Agent Action
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Implementation of Workflow using Mobile Agents

• Integration of XML description and generic
  coordination facility
• Coordination facility - built using
• Ajanta System
• Next
• Ajanta Overview
• Agent Based Implementation environment
• Implementation Issues

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Ajanta Overview

• A Java based framework for programming mobile
  agents
• Agent - an autonomous entity migrating from node
  to node
• Key Features
• Security
• Authentication
• Access Control
• Resource Protection

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Ajanta (cont.)
Agent-Agent Communication
Agent Migration
X
Y
Y
Agent Server 1
Agent Server 2
Server- Server protocol
Host A
Host B
Physical Network
A Mobile Agent System
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Role of Mobile Agents in Workflow

• To encapsulate
• Role specific protocols and interfaces
• Security privileges based on users role and
  identity
• Dynamic alteration of workflow policies by
  updating the mobile agents
• Supporting Disconnected Operations

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Agent-based Implementation Environment

• Plan Creation and Consistency Checking
• XML Plan preparation
• Parsing and Consistency Checking
• Plan Distribution with Authentication
• Role specific Plan Distribution
• Bare User Coordination Interface(UCI) derived
  from AgentServer Class

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(cont.)

• Creation of Role Based User Interface
• UCI populated with objects and user interface
• User Interface - from Convener or
• default generic interface
• Execution of Coordination Operations
• Access Control
• Precondition Check
• Cloning/Agent Action
• Launching of Agents

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Plan Creation and Distribution
User A
User B
3
3
2
2
Convener
XML specifications
1
3
2
Plan Creation and Consistency Checking
Role C
1
Authentication
2
Plan Distribution
3
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System Level View
Role Based User Interface
Generic Coordination Facility
Convener
Get Plan
Get Plan
Role Based User Interface
Role Based User Interface
Generic Coordination Facility
Generic Coordination Facility
User A
User B
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User Coordination Interface
Role Based User Interface
Document Manager
AGENT from a remote users UCI
Proxy
Objects obtained from Convener
AccessProtocol
Agent Environment
UCI Implementation as an Agent Server
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User Interface
User Interface for Author Role
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Execution of Coordination Operations
User A
User B
Communication Network
User Interface
User Interface
a
b
d
c
a
b
d
c
Shared Objects
Shared Objects
Agent-based Coordination Facility
Agent-based Coordination Facility
Dispatching of a Coordination Agent
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Implementation Issues

• Node Serialization not supported by current DOM
  Model
• implemented our own version
• DOM allows only string values to be stored in the
  XML tree

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Conclusion

• Main Contribution methodology for building
  distributed workflow systems using a high level
  specification
• Able to leverage an agent based middleware and
  its security architecture
• Generic Specification for implementing any
  workflow/collaboration

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Future Work

• Dynamic System Behavior
• Dynamic delegation of access rights
• Adding entities to workflow dynamically
• Manipulation of different MIME types of objects
  through User Interface

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XML DTD Plan

• ltPLANgt
• ltROLE ROLE_ID"docauthor"
• ROLE_NAME"author"
• OBJECT_REF"doc"
• ROLE_INTERFACE"ajanta.UserInterface"gt
• ltPRINCIPAL URN"URNansA"/gt
• lt/ROLEgt
• ltROLE ROLE_ID"docreviewer"
• ROLE_NAME"reviewer"
• OBJECT_REF"doc"
• ROLE_INTERFACE"ajanta.UserInterface"gt
• ltPRINCIPAL URN"URNansB"/gt
• ltPRINCIPAL URN"URNansC"/gt
• lt/ROLEgt
• .........
• lt/PLANgt

• lt!DOCTYPE PLAN
• lt!ELEMENT PLAN (ROLE, OBJECT,
• 
  OPERATION)gt
• lt!ELEMENT ROLE (PRINCIPAL)gt
• lt!ATTLIST ROLE
• ROLE_ID ID REQUIRED
• ROLE_NAME CDATA REQUIRED
• OBJECT_REF IDREF REQUIRED
• ROLE_INTERFACE NMTOKEN IMPLIED
• gt
• lt!ELEMENT PRINCIPAL EMPTYgt
• lt!ATTLIST PRINCIPAL
• URN CDATA REQUIRED
• gt
• ......
• gt

Schema and Example for Workflow Plan and Role
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XML DTD Objects

• lt!ELEMENT OBJECT (ACL, STATUS,METHOD, OBJECT) gt
• lt!ATTLIST OBJECT
• OBJ_ID ID REQUIRED
• OBJ_NAME CDATA REQUIRED
• OBJ_TYPE CDATA REQUIRED
• CODE_BASE NMTOKEN "null"
• OBJ_DATA CDATA "null"
• gt
• lt!ELEMENT METHOD ( ACL, PARAMETER)gt
• lt!ATTLIST METHOD
• METHOD_NAME NMTOKEN REQUIRED
• gt
• lt!ELEMENT STATUS OPERATION_PERFORMED)gt
• lt!ELEMENT OPERATION_PERFORMED EMPTYgt
• lt!ATTLIST OPERATION_PERFORMED
• OP_REF IDREF REQUIRED
• OPERATOR CDATA IMPLIED
• gt

• ltOBJECT OBJ_ID"doc"
• OBJ_NAME"Document"
• OBJ_TYPE"multipart/alternative"gt
• ltACL/gt
• ltSTATUS/gt
• ltOBJECT OBJ_ID"docch1"
• OBJ_NAME"Chapter1"
• OBJ_TYPE"multipart/alternative"gt
• ltACL/gt
• ltSTATUS/gt
• ltOBJECT OBJ_ID"docch1content"
• OBJ_NAME"Contents"
• OBJ_TYPE"text/plain"gt
• ....
• lt/OBJECTgt

Schema and Example for Object
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XML DTD Access Control

• lt!ELEMENT ACL (ACL_ENTRY)gt
• lt!ATTLIST ACL
• ACL_NAME CDATA IMPLIED
• ACL_OWNER CDATA IMPLIED
• gt
• lt!ELEMENT ACL_ENTRY ((PRINCIPALGROUP),
  PERMISSION)gt
• lt!ATTLIST ACL_ENTRY
• TYPE (positivenegative) "positive"
• gt
• lt!ELEMENT GROUP EMPTYgt
• lt!ATTLIST GROUP
• ROLE_REF IDREF REQUIRED
• gt
• lt!ELEMENT PERMISSION EMPTYgt
• lt!ATTLIST PERMISSION
• NAME (executeupdateread) "execute"
• gt

• ltACLgt
• ltACL_ENTRYgt
• ltGROUP ROLE_REF"docauthor"/gt
• ltPERMISSION NAME"read"/gt
• ltPERMISSION NAME"update"/gt
• lt/ACL_ENTRYgt
• ltACL_ENTRYgt
• ltGROUP ROLE_REF"docreviewer"/gt
• ltPERMISSION NAME"read"/gt
• lt/ACL_ENTRYgt
• ltACL_ENTRY TYPE"negative"gt
• ltPRINCIPAL URN"URNansC"/gt
• ltPERMISSION NAME"read"/gt
• lt/ACL_ENTRYgt
• lt/ACLgt

Schema and Example for Role Based Access Control
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XML DTD Operation

• lt!ELEMENT OPERATION (ACL, PRE_CONDITION
  (CLONE_OBJECT AGENT_ACTION))gt
• lt!ATTLIST OPERATION
• OP_ID ID REQUIRED
• OBJECT_REF IDREFS REQUIRED
• OPERATION_NAME NMTOKEN REQUIRED
• gt
• lt!ELEMENT PRE_CONDITION EMPTYgt
• lt!ATTLIST PRE_CONDITION
• OP_REF IDREFS REQUIRED
• gt
• lt!ELEMENT CLONE_OBJECT (TARGET)gt
• lt!ELEMENT TARGET EMPTYgt
• lt!ATTLIST TARGET
• ROLE_REF IDREFS REQUIRED
• gt

• ltOPERATION OP_ID "docch1conpublish"
• OBJECT_REF"docch1content"
• OPERATION_NAME"Content_Publish"gt
• ltACLgt
• ltACL_ENTRYgt
• ltGROUP ROLE_REF"docauthor"/gt
  
• ltPERMISSION/gt
• lt/ACL_ENTRYgt
• lt/ACLgt
• ltCLONE_OBJECTgt
• ltTARGET ROLE_REF"docreviewer"/gt
• lt/CLONE_OBJECTgt
• lt/OPERATIONgt

Schema and Example for Operation