Native

XML

Business Process Execution

for

Computer Supported

Mobile

Adaptive

Business Processes

Thomas Hildebrandtassociate professor, ITU

Komialt seminar, ITU, Dec 5th, 2006

FTP research project 2007 - 2010 Kjeld Schmidt, Henning Niss and Mikkel Bundgaard (ITU)

& Microsoft Development Center Copenhagen

Road Map

The Computer Supported Mobile Adaptive Business Processes (CosmoBiz) research project

Traditional Business Process Models and execution

Challenges for Pervasive Business Processes

Native XML BP execution and formalisation

Computer

Supported

Mobile

Adaptive

Business Processes

ITU

&

Microsoft

Development

Center

Copenhagen

Interdisciplinary research project combining industrial prototyping and research in formal models and computer supported cooperative work

Starts january 1st, 2007 and runs for 4 years.

2 PhDs and 1 year postdoc funded by the danish research agency for technology and production

Relates to 2 industrial PhD projects: Danske Bank (MDBP) and Resultmaker (Clinical Workflows)

Work packages

Models of Business Processes

BPMN WS-BPEL

Model-based design, e.g. from graphical flow-chart notation to XML-based execution language

Traditional architecture

The WfMC reference model

Business Process Execution

business processes are long-lived

process state is persisted

- traditionally in a proprietary relational format

The informal semantics is hidden in the process execution engine

Challenges for Pervasive BPM

context-dependent, mobile business process instances ?

(static) guarantees for correctness and security ?

(higher-order) processes for process management ?

evolution and adaption of business process languages ?

How do we support:

Our working thesis

Business process instances must be exchangeable,

the execution semantics must be formalised to support consistent execution on different devices and advanced programming language concepts such as types, mobile and higher-order processes,

and the formalisation must be extensible and close to the language and its implementation to support language evolution, engineering (e.g. exploring new features based on CSCW field studies and formal models) and execution in practice

A possible solution

Formalise process execution using theory of graph-rewriting and process calculi, implemented as XML-rewriting and persisted in XML-store

Proof of concept: A formalized native XML execution of BPEL implemented on top of a peer-to-peer XML persistence layer

Described in two ITU MSc thesis projects and presented at the International workshop for models and tools for coordination (MTCoord) in 2005 and the COORDINATION conference in 2006

Graph rewriting systemsA graph rewriting system consists of a definition of the valid graphs and a set of rules of the form (L→R) specifying that a sub graph L can be replaced with the sub graph R

Example: Petri Net can be seen as an instance of a graph rewriting system

Christian Stahl has provideda complete Petri netsemantics for BPEL 1.1:

graphical & extensive tool support,but not easily extensible, nor as close to the language as one could hope for!

Process CalculiA process calculus is a formal textual notation for (usually concurrent communicating) processes equipped with rewrite rules for execution and a theory of relating processes (e.g. simulation)

Example:The pi-calculus is a famous example of a process calculus for communicating processes with dynamic communication channels

Lapadula, Pugliese and Tiezzi have proposed a WS-process calculus:

- supports WSDL type system, but not easily extensible

Bigraphical Reactive Systems

and Reactive XML

A bigraph is a collection of trees (the place graph) with links (the link graph)

Bigraphical Reactive Systems (Robin Milner, 2001)

is a graph rewriting framework (and theoryof simulation) for bigraphs inspired by thepi-calculus but also able to describe Petri Net

Incidentally, bigraphs correspond closely to XML data and thus the syntax of BPEL, e.g.:

<instance name=”transfer”> <variables> <variable name=”accountA”>P1</variable> <variable name=”accountB”>P2</variable> </variables> <sequence> <assign><copy><from var=”accountA”/> <to var=”accountB”/> </copy> </assign> P </sequence></instance>

XML corresponding to the example bigraph

Example bigraph for BPEL process instance

Native XML BPEL execution as (bi)graph

rewritingThe idea: Combine the process description and state and execute by rewriting as in theory of process calculi and graph-rewriting

persist, distribute and exchange process instances as XML

- a word on the XML persistence layer

(XMLstore)

never destroys data, but shares subtrees, e.g:

maintains complete history (e.g. for transactions) and easy replication (e.g. for P2P distribution)

XML process calculus

we use a shorter process calculus notation (maps 1-1 to XML)

maps to

so we introduce a “next” node to record the order of actions in sequence

Technical note: sibling nodes of bigraphs are unordered (expressed by P | Q ≡ Q | P )

A system consists of a set of processes and instances in parallel:

Instances are defined as processes except allowing values for variables:

The BPEL subset

computation steps can be described as bigraphical reactions

specified by a set of parametric rewrite rules L→R (e.g. parametric in the variable names, content and context)

Formalising computation steps

Semantics of assignment (in process calculus notation)

Semantics of exit

Rewrite rule examples

From BPEL to Bigraphs & back

Summary

XML rewriting framework called Reactive XML formalised as Bigraphical Reactive Systems and distributed P2P implementation using value-based XML persistence layer (MTCoord Workshop, 2005)

BPEL case: process language, formalisation and implementation closely connected - and extensible(Coordination Conference 2006)

ITU Technical Report TR-2006-85.(extended, submitted journal version available)

The architecture for pervasive BPM?

Perspectives & Future Work

Extensible platform for distributed (business) process language engineering, execution, CSCW & coordination

Future (partly covered by the CosmoBiz project)

Full BPEL semantics and implementation

Model-based development (i.e. transformations from BPMN/UML to BPEL)

Typed, mobile and higher-order processes

CSCW studies in adaptive, context-dependent, mobile business and work flow processes, e.g. sales services and clinical workflows

Formal reasoning & verification

Quantitative semantics: Time and probabilities (with M. Kwiatkowska)

Relate to other graph rewriting frameworks (R. Heckel, graph rewriting)