XML-based supply chain integration: a case study

This paper describes experiences gained from the implementation and evaluation of an XML-based integration system in a real case. The prototype was designed to support electronic data exchange in a supply chain. The purpose of the prototype was to study the properties of the integration system from both a development and usage perspective . In particular , the study outlined how and in which circumstances XML facilitates supply chain integration. EDI provided a point of comparison. This information is useful both for the developers and users of integration systems. Received October 2001 Revised June 2002 Accepted July 2002 This work was partly funded by the European Commission through the IST Project GNOSIS-VF: Towards the Virtual Factory: Delivering Configuration, Scheduling and Monitoring Services through a Web-Based ClientServer Architecture. The authors thank their colleagues Stefan Jakobsson, Kalle Kuhakoski and Martin Ollus as well as their industrial partners ABB Control and InCap Electronics. 1 Plan: demand/supply planning. 2 Source: sourcing/material acquisition, manage sourcing infrastructure. 3 Make: production execution, manage make infrastructure. 4 Delivery: order management, warehouse management, transportation and installation management, manage deliver infrastructure. This model requires integration of participants in the supply chain. These participants are not just different sites within the same company but they often belong to different companies. The latter case is in many ways much more difficult than the former one. In all, supply chain management is about integration. Requirements ABB Control has a switchgear factory located in Vaasa, Finland. ABB Control is part of the world-wide ABB group and it produces switchgear assemblies for both internal and external use. The case is based on the idea that the functionality of an in-house information system can be expanded to support supply chain integration. The geared functionality of the integration system will cover the functionality that is related to production management and purchasing with respect to internal and external resources. ABB Control’s business process model related to the execution of customer orders is quite traditional. Generally, ABB Control uses internal resources to carry out production, but in production overload situations it has to use external resources, which may be either other ABB companies or local subcontractors. The combination of internal and external production resources forms a supply chain. The basic idea behind such co-operation is the flexible transparency of internal and external production resources. Production management has the possibility of planning external resources as internal ones. The expected business benefits from supply chain integration are related to improved production flexibility and more profitable data exchange. Figure 1 illustrates a co-operation model in which a subcontractor produces ABB-specific products, whereas a supplier does not. The co-operation model of supply chain integration can mainly be implemented with current software technologies. A number of commercial integration systems (see e.g. Microsoft, 2002) are available. However, taking into account the unstable status of the new technologies, the case gives an opportunity to design and implement a prototype of the integration system. The objective is to achieve the prototype that can be easily maintained and used, and to utilise XML-technologies. The purpose is for XML to be used to extend supply chain integration to those subcontractors who have not accepted EDI. The architecture of the prototype is based on the following model. A central part of this architecture is a server that supports EDI, XML, or both. Clients of this server can be browsers, other integration systems, or applications. This is not the only possible model but many commercial integration systems at least partially conform to this architecture. The implementation of supply chain integration requires the design of the required semantic message models and their interaction-handling logic. The content of the messages can be based on XML-based e-business frameworks (BizTalk, 2002; ebXML, 2002; RosettaNet, 2002; xCBL, 2002). A large number of potentially useful interactions are identified in the context of supply chain integration (GNOSIS-VF, 2001d). In this case, the objective is for the prototype to be capable of performing the following interactions: ABB sends a specific purchase order to a specific subcontractor. Query the database for an order, translate the order from the EDI segments to the xCBL format, send this order as an e-mail or a message to a subcontractor, and return success/failure. A subcontractor queries for one of its purchase orders. Query the database for an order, translate the order from the EDI segments to the xCBL format, and return the order. A subcontractor queries for a list of all its purchase orders. Query the database for orders, translate the orders from the EDI segments to the XML format, and return a list. A subcontractor updates a purchase order response into a database of ABB. Translate an order response in the xCBL format to INSERT statements for EDI segments, update the database, and return success/failure. A subcontractor updates an invoice into a database of ABB. Translate an invoice in the xCBL format to INSERT statements for EDI segments, update the database, and return success/failure. A subcontractor queries for a demand forecast of its possibly forthcoming purchase orders. Query for forthcoming orders, translate the forthcoming orders from the EDI segments to the XML format, and return a demand forecast. [ 587 ] Juha-Miikka Nurmilaakso, Jari Kettunen and Ilkka Seilonen XML-based supply chain integration: a case study Integrated Manufacturing Systems 13/8 [2002] 586±595 All these interactions, except the last one, are used as a starting point in the design and implementation of the prototype. They were suggested by ABB Control. The final interaction is applied after implementation to evaluate the maintainability of the prototype. It was identified after implementation and suggested by InCap Electronics. xCBL (version 2.0) is utilised in the case because it provides XML-based business documents for the chosen interactions and is interoperable with EDI. XSLT is needed to make the necessary transformations between XML and EDI formats. XML-technologies XML The Extensible Markup Language (W3C, 2002a) is designed to improve the functionality of the Internet by providing flexible information structuring. XML is extensible because it is not a fixed format like HTML but a metalanguage for describing other languages. XML can be utilised to design customised mark-up languages for different types of documents. XML is a subset of SGML, with some exceptions. SGML is a standard for defining descriptions of the structure of an electronic document. SGML is very powerful but complex, whereas XML is a lightweight version of SGML that removes all the features making SGML too complex for the Internet. The XML standard defines the syntax of a mark-up language that is applied to represent the structure of an electronic document. These documents are composed of a set of objects that may contain elements. Each element may have a number of attributes, according to which the document will be processed. XML provides a formal syntax to describe the dependencies between the objects, elements and attributes, and to build an electronic document. The XML document has to be well formed or valid. The document is well formed if each non-empty element has a start-tag and an end-tag between tags of its parent element. The document can be validated by DTD, which defines elements of the document and a hierarchical order between them. DTD also defines attributes of the elements and values of the attributes. XSLT The Extensible Stylesheet Language Transformations (W3C, 2002b) is a language for transforming XML documents into other XML documents. XSLT is not intended as a completely general-purpose XMLtransformation language but it is designed for use as a part of XSL, which is a stylesheet language for XML. XSL includes an XML vocabulary for specifying formatting. A transformation expressed in XSLT describes rules for transforming a source document into a result document. This stylesheet contains a set of template rules, which consist of patterns and templates. This allows a stylesheet to be applicable to a wide class of documents that have structures similar to the source document. A pattern is matched against elements in the source document. A template is instantiated to create part of the result document that is separate from the source document. In constructing the result, elements from the source can be filtered and reordered, and arbitrary structure can be added. xCBL The Common Business Library (xCBL, 2002) is a set of XML building blocks and a document framework that allows the creation of reusable XML documents for e-business. Although XML provides a selfdescribing document, stronger data typing and validation for e-business transactions is needed. In addition, there is a proliferation of industry-specific elements that would potentially lead to problems. xCBL is a combination of the leading XML industry initiatives and most common cross-industry XML elements. Fundamental documents, such as orders and invoices, and elements, such as country codes and currencies, have been captured in xCBL. Since the applications are heterogeneous, integration would have to take place at a semantic level where components communicate through a common language, vocabulary, and business concepts. xCBL is not a single standard but a collection of Figure 1 A co-operation model [ 588] Juha-Miikka Nurmilaakso, Jari Kettunen and Ilkka Seilonen XML-based supply chain integration: a case study Integrated Manufacturing Systems 13/8 [2002] 586±595 common business elements that underlie all EDI and Internet protocols. xCBL has been developed after EDI semantics, such as EDIFACT. Its reusable components should speed the implementation and facilitate interoperation by providing a common semantic framework.