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The Application of XML-Based Markup Languages in Enterprise Process Modeling

Manjunath Kamath, Nikunj P. Dalal, and Ramasamy R. Chinnanchetty Oklahoma State University

Stillwater, OK 74078, USA Abstract

Extensible Markup Language (XML) is quickly becoming the universal format for structured documents and data on the Web. XML is actually a metalanguage that has spawned the creation of numerous domain-specific, industry- standard markup languages, each having its own set of user-defined tags and attributes. XML is also a family of technologies such as the Extensible Style Sheet Transformation Language (XSLT) designed to transform an XML document into another XML document. In this paper, we survey specific XML-based markup languages for enterprise process modeling. We also discuss, in the context of an ongoing NSF-funded research project, the role of XML and related technologies in supporting a distributed, Web-based, collaborative framework for enterprise process modeling.

Keywords

XML, Markup Languages, Process Modeling, Enterprise Modeling.

1. Introduction

Extensible Markup Language (XML) “is the universal format for structured documents and data on the Web”

(www.w3.org). Markup takes the form of words between angular brackets, called tags, e.g., <first_name> and

<phone>. Markup entities or elements normally consist of an opening tag and a closing tag, e.g., <first_name> and

</first_name>. By describing the enclosed information, tags make an XML document self-documenting. Thus, XML adds context and gives meaning to data. HTML, on the other hand, is concerned with the presentation of data.

Both HTML and XML were derived from the Standard Generalized Markup Language (SGML), an international standard format for embedding descriptive markup in a document and describing the document structure [12]. XML is extensible because it is a metalanguage – a language for describing other languages. XML lets us define our own custom tags so that we can define customized markup languages for any document or application. Hence, XML has spawned the creation of numerous domain-specific, industry-standard markup languages, each having its own set of user-defined tags and attributes. This aspect of XML is central to the theme of this paper. An XML-based markup langauge is used to capture and store an enterprise process model description created by using a graphical process modeling language.

XML is also a family of technologies, which includes, among others, (i) the Extensible Stylesheet Language (XSL), which allows us to apply rules for formatting, including presentation format, to XML documents, (ii) the Extensible Stylesheet Transformation Language (XSLT) designed to transform an XML document into another XML document, and (iii) Xlink, which describes a standard way to add hyperlinks to an XML file [18, 19]. The output of an XSLT transformation could take the form of XSL formatting objects that are rendered to hard copy, to a screen device, to an audio device, and/or a Web page. Transformation using XSLT will play a key role in configuring various models from an XML-based description of enterprise processes, for analysis purposes.

An XML file is a text file that is portable across various platforms and languages. Problems encountered due to the heterogeneity of architectures and platforms can be overcome with XML. It can be used to pass message requests and responses across any environment. It is an excellent format for exchanging data between applications, especially when dealing with loosely connected applications. XML is already having a major impact on the development of next-generation business-to-business (B2B) e-commerce applications. For example, trading partners can use a standardized XML syntax to describe business documents like purchase orders and invoices, and automate their transfer across the Internet.

1.1 Enterprise Process Modeling

An enterprise is a complex entity composed of people and processes, producing products or services for customers.

Enterprise modeling is concerned with the representation and specification of the various aspects of an enterprise’s

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operations [1]. The main aspects are (1) functional aspects that describe what things are to be done and in what order; (2) informational aspects that describe which objects are used or processed; (3) resource aspects that describe what or who performs things and according to which policy; and (4) organizational aspects that describe the organizational structure within which things are to be done [23]. Within the context of enterprise modeling, business process modeling and activity modeling play a central role. Enterprise behavior concerns the order in which things are to be executed (i.e., the flow of control). It is described in terms of business processes. Enterprise functionality concerns the things to be done (i.e., the functions – either transformational or decision-making). It is described in terms of enterprise activities [23].

Our interest is in modeling enterprise functionality and behavior for the purpose of enterprise/process improvement and redesign. The ultimate goal of our effort is to develop process-modeling capabilities, which offer accurate, precise, and timely decision support for improvement efforts within dynamic business/technical environments.

Business processes hold the key to the future success of enterprises; it is the business process that operates on business data to accomplish the enterprise’s business objectives and give the enterprise a competitive edge. With recent advancements in information technology, there is an increased interest in techniques, existing and new, for modeling, specification, implementation, maintenance, and performance improvement of business processes [14].

Another facet of enterprise functionality and behavior is workflow management, which includes both business process specification and automated execution of business procedures. Workflow management is a next-generation extension to business process modeling efforts that emphasizes the increased role that information systems have come to play in today’s businesses [20]. Workflow Management involves two phases – (i) the modeling phase that abstracts from business procedures and defines computer-implementable workflow specifications, and (ii) the execution phase that executes instances of the workflows to meet business requirements, and both these phases are managed and coordinated by a Workflow Management System (WfMS) [6]. The growing interest in workflow management has led to the creation of many software products, each championed by its own set of vendors, and file- formats, etc. In an effort to standardize terminology, and enable inter-operability between different vendors, the Workflow Management Coalition (WfMC), an international consortium founded in 1993, has established standard reference architectures that software vendors have to conform to, and basic terminology as would be essential for any process modeling language, amenable to computerization [6, 24].

In this paper, we examine the important role that XML-based markup languages play in enterprise process modeling. In section 2.0, we present markup languages developed especially for process modeling and specification and work flow management. In section 3.0, we discuss how XML and related technologies could be used to support a distributed, Web-based, collaborative framework for enterprise process modeling by describing the progress made on an ongoing NSF-funded project.

2. XML-based Markup Languages for Process Modeling and Workflow Management

As mentioned earlier, XML is a metalanguage that allows user to develop their own XML-based language, supported with customized markup tags. The user is referred to the W3 Web site (www.w3.org) for a listing of other developments related to XML. Here, we briefly present some of the markup languages related to business process modeling and specification, as well as workflow management.

2.1 Process Specification Language (PSL)

PSL, a Process Specification Language based on XML, is being developed by the National Institute of Standards and Technology's Manufacturing Systems Integration Division. PSL primarily focuses on the manufacturing process encompassing the entire life cycle of the product, from design process to production planning and control [17]. The XML representation of PSL semantics employs the Resource Description Framework (RDF) schema language [13].

2.2 Business Process Modeling Language (BPML)

BPML provides an abstracted execution model for collaborative and transactional business processes that span multiple applications and business partners, behind the firewall and over the Internet, and across multiple verticals [2]. BPML is an XML schema that provides a standard way to model mission-critical business processes. The first draft of BPML covers transactions and compensating transactions, dataflow, messages and scheduled events, business rules, security roles, and exceptions. The Business Process Modeling Language will enable the enterprise to model, deploy, and manage business processes such as order management, customer care, demand planning, product development, and strategic sourcing.

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2.3 Electronic Business eXtensible Markup Language (ebXML)

ebXML is a framework of specifications that enables businesses to collaborate electronically and implement a complete e-business solution [4]. The ebXML defines the business processes and associated roles and activities, creating and publishing business profiles in a registry, storing business information in a repository, searching for other business partners, agreeing trading protocols, creating business documents, and sending them via secure and reliable messaging systems. ebXML provides a standard way to manage collaborative business processes (CBP). It is maintained by industry consortia (OASIS and UN/CEFACT) and allows companies to benefit from electronic trading via a global network, regardless of size or geographical location, both within and across industries.

2.4 eXchangeable Routing Language (XRL)

XRL is an instance-based workflow language that uses XML to represent process definitions and Petri nets for its semantics [22]. A routing element is an important building block of XRL, and it includes task, sequence, choice, condition, parallel-sync, and stop, among others. XRL is designed to support inter-organizational business processes such as those arising in the context of B2B e-commerce. Unlike traditional workflow modeling languages that are class or type-based, XRL is instance based. Workflow definitions can be changed on-the-fly and sent across organizational boundaries. Such features are considered to be vital for today’s dynamic and networked economy.

However, such on-the-fly-changes coupled with the perils of “open” e-commerce, e.g., doing business with other firms without prior trading relationship, are likely to result in logical errors. Since XRL semantics are expressed in terms of Petri nets, powerful analysis techniques can be used for verifying the XRL workflows. Based on XRL, a workflow management system called “XRL/Flower” has been developed that includes verification of soundness of workflow processes using Petri nets.

2.5 Wf-XML Protocol

In an Internet-scale workflow, a large number of companies and processes could be linked because each individual company may support only a small part of the process, referring to other parts via URL-style links [5]. Lack of standardization in interfaces, due essentially to custom designed programs, is a barrier to the smooth execution of such collaborative activities. The Wf-XML message set and protocol, currently maintained by the WfMC, represents an attempt to provide a simple protocol that enables interaction between requesters and providers of workflow-type services [5]. Wf-XML focuses on a subset of SWAP (Simple Workflow Access Protocol), which was a WfMC initiative to define an Internet-based workflow access protocol to instantiate, control, and monitor workflow process instances. Wf-XML specification represents the next step in the evolution of workflow interoperability standards and builds on the semantic and extensibility properties of XML. An extension of Wf- XML has been proposed [9] that specially targets the workflow requirements of electronic commerce systems.

3. The Distributed Integrated Modeling of Enterprises (DIME) Framework

Since the development of data flow diagrams (DFDs) and the IDEF family of techniques in the 1970s, process modeling has been an active area of research [10]. A comparative evaluation of these and several newer process modeling techniques was presented in the 2001 IERC, wherein several inadequacies of existing modeling techniques were identified when it comes to the distributed, Internet-driven, open, and collaborative nature of modern business transactions [7]. An ongoing NSF-funded research effort builds on existing process modeling approaches to provide an integrative framework for enterprise process modeling. We call this the Distributed Integrated Modeling of Enterprises (DIME) Framework. Many of the shortcomings of existing techniques are addressed with the help of Petri net theory, and by integrating modern concepts such as activity-based management, linkages between engineering and business approaches, and the distributed computing paradigm of the Internet [8].

Our vision for this framework is a Web-based environment in which enterprise users will define, modify, and analyze business processes using user-oriented modeling applications resident on Web clients. Business process models will be translated into formal models using the underlying Petri net-based constructs. The formal representation of the enterprise’s business processes will be stored on enterprise servers. The Web-based clients will address the needs of diverse enterprise users, ranging from the managerial to the technical. Server applications will store and manipulate the formal representations and also perform qualitative and quantitative analyses using formal models to support process improvement initiatives.

A laboratory implementation of the new framework is underway. The front-end is based on a graphical process modeling language that we have developed [8]. Concepts from process improvement methods such as activity-based

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costing and process-value chains, as well as distributed computing features are being integrated with the classical process modeling constructs of control flows, data flows, and process descriptions. The syntax and semantics of this language also incorporate the knowledge derived from Petri net representations of workflow constructs [21]. The linkage between Petri net theory [3], and the graphical process modeling language in a Web context represents a corner stone in the establishment of a scalable theoretical foundation for user-oriented enterprise process modeling.

The power of the underlying Petri net representations is clearly evident when it comes to the use of logical operators. To illustrate, the Petri net representation can quickly detect the presence of ambiguous logic and provide immediate feedback to the user.

The direct business model of a hypothetical enterprise, HAL Computer Corporation, was used to facilitate the development of the graphical process-modeling language, the two-way mappings, and the proof-of-concept prototype. The working example included the following high-level processes and their expansions - product selection and customer order placement; customer order processing and vendor order placement; and manufacturing.

Parts of a working example, illustrating the different models and representations, are shown in Figure 1.

Figure 1. Parts of a Working Example from Ongoing Work 3.1 The Role of XML in the DIME Framework

Ongoing development of the DIME framework will focus on three distinct layers – a descriptive layer, a scalable representation layer, and an enterprise analysis layer. The descriptive modeling layer includes the graphical front- end language mentioned earlier, which we define as the DIME Descriptive Modeling Language (DDL). DDL incorporates many user-oriented features and uses a novel, tiered approach for enterprise process modeling.

The scalable representation layer is so named because it contains computer-processable representations that enable internal user groups as well as supply-chain partners to share information about processes. This layer includes the XML representations of the descriptive and formal models as well as the DIME mappings that are achieved between these representations. The XML representation of the descriptive model is captured using the DIME Markup Language (DML). DML is automatically created from the DDL using a browser-resident program. We have developed a preliminary markup language using XML to represent the basic modeling constructs of DML with sets of hierarchical nested tags. The DML will be accompanied by the creation of reusable XML schema for validation.

XML schema is a language for describing the components and rules of a language like DML. Each time the user creates or modifies a DDL model, it is automatically validated for consistency of data structures against the XML- schema before it can be automatically mapped to the DML representation. The XML parser module present in the Web browser flags all errors. A new XML schema can be made from libraries of schema. So, the need to build new XML documents from scratch is reduced when the size and complexity of the enterprise system increase over time.

<process ID= "1"type= "HAL's Ordering Process">

<activity id= "1.1">

<name>Configure Computer</name>

<activity id= "1.1.1">

<name>Select Computer Type</name>

...

...

</activity>

</process>

Process Models XML Representation

P1 P2 P3

Select Computer Type(T1)

Configure Laptop (T2)

Configure Desktop (T3)

Petri Net Modeling and Analysis

Configure Computer

H, C

1.1

Submit Payment

M

1.2 Mailing Address

Credit Card details

Purchase Order Number

XOR

Select Computer

Type

H,C

1.1.1 Configure

Desktop

H, C

1.1.3 Configure

Laptop

H,C

1.1.2

XOR

(HAL's Ordering Process)

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<?xml version="1.0" encoding="utf-8"?>

<xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">

<xsd:element name="dml">

<xsd:complexType>

<xsd:sequence>

<xsd:element name="activity" minOccurs="0" maxOccurs="unbounded">

<xsd:complexType>

<xsd:sequence>

<xsd:element name="name" type="xsd:string"/>

<xsd:element name="resources" type="xsd:string"/>

<xsd:element name="from" type="xsd:string"/>

<xsd:element name="to" type="xsd:string"/>

<xsd:element name="input" minOccurs="0" maxOccurs="unbounded">

<xsd:complexType>

<xsd:attribute name="flow" type="xsd:string"/>

</xsd:complexType>

</xsd:element>

<xsd:element name="output" minOccurs="0" maxOccurs="unbounded">

<xsd:complexType>

<xsd:attribute name="flow" type="xsd:string"/>

</xsd:complexType>

</xsd:element>

. .

</xsd:element>

Schema for DML (Dime Markup Language)

The Transformation Code

<?xml version="1.0" encoding="utf-8" ?>

<xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">

<xsd:element name="PNML">

<xsd:complexType>

<xsd:sequence>

<xsd:element name="transition" minOccurs="0" maxOccurs="unbounded">

<xsd:complexType>

<xsd:sequence>

<xsd:element name="name" type="xsd:string" /

>

<xsd:element name="resources"

type="xsd:string">

<xsd:element name="arc">

<xsd:element name="source"

type="xsd:string" />

<xsd:element name="target"

type="xsd:string" />

</xsd:element>

<xsd:element name="input"

minOccurs="0"

maxOccurs="unbounded">

<xsd:complexType>

. .

</xsd:element>

Output PNML File

<?xml version="1.0" encoding="iso-8859-1"?>

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">

<xsd:schema xmlns:xsd="http://www.w3.org/2000/10/XMLSchema">

<xsd:element name="PNML">

<xsd:complexType>

<xsd:sequence>

<xsd:element name="transition">

<xsl:attribute name="minOccurs"><xsl:value-of select="xsd:schema/ xsd:element/xsd:complexType/

xsd:sequence/xsd:element/@minOccurs"/></xsl:attribute>

<xsl:attribute name="maxOccurs"><xsl:value-of select= "xsd:schema/ xsd:element/xsd:complexType/

xsd:sequence/xsd:element/@maxOccurs"/></xsl:attribute>

<xsd:complexType>

<xsd:sequence>

<xsd:element name="name">

<xsl:attribute name="type"><xsl:value-of select= "xsd:schema/ xsd:element/xsd:complexType/

xsd:sequence/xsd:element/xsd:complexType/xsd:sequence/xsd:element/@type"/></xsl:attribute>

. .

</xsd:element>

Figure 2. DML to PNML Translation: An Example

The other XML representations within this layer are for (1) Petri net models, (2) other formal models such as queueing and simulation, and (3) formal views, such as cost, resource, and productivity views. With Petri nets providing the theory base, the two-way mapping between the DML and the Petri net representation is fundamental to our approach. Our mapping scheme has polynomial complexity and in many cases generates a Petri net model that has a one-to-one correspondence with the descriptive model. The mapping from DML to PNML, the Petri net Markup Language (and other similar DIME mappings from DML to other markup representations) is achieved by means of XSL Transformations – Figure 2 illustrates an example. The transformation code specifies the set of rules that produces the output document from the input XML document. A transformation written in XSLT is called a style sheet. The style sheet is made up of template rules, which have two parts, a ‘pattern’ that is matched against the nodes in the source document and a ‘template’ that can be instantiated to form the result document.

The proposed DIME framework is highly scalable, flexible, and robust for many reasons. First, the Web-based creation, management, and use of models, enables users from different locations to work independently on parts of the same enterprise process model. The existing model is not affected by the addition of a new sub-model or by the addition of a new group of users assigned to modeling a different set of processes. Once the new sub-model is created, it can be linked to the existing model via an appropriate parent process by the owner of the parent process.

Second, the XML-based scalable representation layer is flexible, yet powerful. With the help of the DIME mappings, this layer will 1) enable models created by different users to be aggregated automatically in a platform and machine independent manner, 2) allow other members of the supply-chain to share and access the enterprise model as needed, and 3) enable the use of Petri net theory, queueing theory, and other formalisms to access, analyze, and modify the enterprise process model. Third, the DIME descriptive modeling language (DDL) will enable us to

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compactly capture the semantics of all business processes for a variety of enterprises, whether they be traditional manufacturing firms, extended/virtual enterprises or parts of a supply chain. The XML-based DIME Markup Language and the XSLT-based DIME mappings at the scalable representation layer of our framework are expected to be significant contributions to the theory and practice of enterprise systems and collaborative commerce. They serve as precursors to the development of a futuristic standard enterprise modeling and analysis markup language.

Acknowledgements

We gratefully acknowledge the funding support provided by the National Science Foundation through grant # DMI- 0075588 under the Scalable Enterprise Systems Initiative. We also thank Mr. Karthik Ayodhiramanujan and Mr.

Eswar Sivaraman for their assistance during the preparation of this paper.

References

1. Bernus, P., Nemes, L., and Morris, R., 1996, “The Meaning of an Enterprise Model,” in Modelling and Methodologies for Enterprise Integration, Bernus, P. and Nemes, L. (eds.), Chapman & Hall, UK, 183-200.

2. Business Process Management Initiative <http://www.bpmi.org>

3. David, R. and Alla, H., 1991, “Petri Nets for Modeling Dynamic Systems” Automatica, 30(2), 175-202.

4. Electronic Business XML< http://www.ebxml.org >

5. Hayes, J.G., Peyrovian, E., Sarin, S., Schmidt, M.-T., Swenson, K.D., and Weber, R., 2000, “Workflow Interoperability Standards For The Internet,” IEEE Internet Computing, 4(3), 37-45.

6. Hollingsworth, D., 1995, “The Workflow Reference Model,” published by the Workflow Management Coalition, Document TC00-1003, available athttp://www.wfmc.org/standards/docs.htm.

7. Kamath, M., Dalal, N., Kolarik, W., Chaugule, A., Sivaraman, E., and Lau, A., 2001, “Process-Modeling Techniques For Enterprise Analysis And Design: A Comparative Evaluation,” IERC 2001 Proceedings.

8. Kamath, M., Dalal, N., Kolarik, W., Lau, A., Sivaraman, E., Chaugule, A., Choudhury, S., Gupta, A., and Channahalli, R., 2002, “An Integrated Framework For Process And Performance Modeling Of Next-Generation Enterprise Systems: Design And Development Issues” Proc. of the University Synergy Program (USP) Conf.

9. Kanaya, N., Hara, H., Nomura, Y., Komori, H., and Ebata, T., 2000, “Distributed Workflow Management System for Electronic Commerce,” Proc. of 4th Intl. Enterprise Distributed Object Computing Conf., 150-159.

10. Kateel, G., Kamath, M., and Pratt, D., 1996, “An Overview Of CIM Enterprise Modeling Methodologies,”

Proceedings of the 1996 Winter Simulation Conference, IEEE, 1000-1007.

11. Keller, G. and Detering, S., 1996, “Process-Oriented Modeling and Analysis of Business Processes Using the R/3 Reference Model,” in Modelling and Methodologies for Enterprise Integration, Chapman & Hall, 69-87.

12. Khare, R., and Rifkin, A., 1997, “XML: A Door To Automated Web Applications,” IEEE Internet Computing, 1(4), 78-87.

13. Klein, M., 2001, “XML, RDF, And Relatives,” IEEE Intelligent Systems, 16(2), 26-28.

14. Knowles, G., 1999, “Next Generation Enterprise Modeling: A Step Beyond Baan Application Modeling,” Baan Brothers Foundation 2ndRoundtable Proceedings, Utrecht, The Netherlands, 95-115.

15. Lenz, K., and Oberwise, A., 2001, “Modeling Interorganizational Workflows With XML Nets,” Proc. of the 34thAnnual Hawaii International Conf. on System Sciences, Jan. 3-6, 2589-2598.

16. Murata, T. 1989, “Petri Nets: Properties, Analysis and Applications,” Proceedings of the IEEE, 77, 541-580.

17. National Institute of Standards and Technology <http://www.mel.nist.gov/msidstaff/lubell/pslxml/>

18. Roy, J., and Ramanujan, A., 2000, “XML: Data’s Universal Language,” IT Professional, 2(3), 32-36.

19. Roy, J., and Ramanujan, A., 2001, “XML Schema Language: Taking XML To The Next Level,” IT Professional, 3(2), 37-40.

20. Sheth, A., Aalst, W.M.P., and Arpinar, I. (1999), “Processes Driving the Networked Economy,” IEEE Concurrency, 7(3), 18–31.

21. van der Aalst, W.M.P. (1998), “The Application of Petri Nets to Workflow Management,” The Journal of Circuits, Systems, and Computers, 8(1), 21–66.

22. van der Aalst, W.M.P., Verbeek, H.M.W., and Kumar, A., 2001, “Verification of XRL: An XML-Based Workflow Language,” Proc. of the Sixth International Conf. on Computer Supported Cooperative Work in Design, July 12-14, Ont., Canada, 427-432.

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24. WfMC, 1999, “Terminology & Glossary,” published by the Workflow Management Coalition, Document WFMC-TC-1011, available athttp://www.wfmc.org/standards/docs.htm.

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