Open source enterprise connection

Dennis Brandl, BR&L Consulting -- Control Engineering, 9/1/2004

I received some comments about my column on free software (April 2004), and I believe some clarification is needed. Although the term "free software" may be legally correct when defining software that can be freely modified but may have fees, it has been a marketing disaster. It was difficult to explain to end-users that their free software actually costs money. Fortunately, the term now used by most developers and users is "open source software." Common open source licenses are the GNU Public License (GPL) and the Lesser GPL. Software released under the GNU Public License (GPL) and the Lesser GPL can be freely distributed, modified, and copied; however, the source code must be made available and derivative works that are publicly distributed must follow the same license. The Lesser GPL is the most useful because it allows the software to be used in commercial products, provided the source code is also made available.

One significant new piece of open source software for manufacturing systems was just released under the Lesser GPL license by Cervecería Polar, the beer and malt business unit of Empresas Polar, a major Venezuelan food and beverage company. An interface between plant floor production systems and SAP R/3 business systems, this software is based on XSLT, the eXtensible Stylesheet Language Transformation. It converts SAP's interface files into industry standard XML files and XML files into SAP interface files.

Industry standard XML is based on B2MML, the Business to Manufacturing Markup Language (B2MML implements the ANSI/ISA 95.01 and IEC 62264-1 standards for manufacturing-to-business integration). The B2MML XML schemas were released as open source software through the World Batch Forum (www.wbf.org) and the Cervecería Polar XSLT code will also be available from the WBF Web site.

Cervecería Polar used this software to connect its SAP system to multiple, MES, PLC, and DCS configurations in only five weeks. Projects of this magnitude usually take up to a year to complete. The project was successful because of open source software and the volunteer support the open source authors provided. This project shows the benefit of open source software when commercial alternatives are not available or are available only for limited systems. Most SAP interface products work only with a single PLC, DCS, data historian, or MES system. The open source solution can now be used by any end-user and even may be incorporated in commercial products.

XSLT should be one of the tools in the manufacturing IT professional's toolkit. It is a general purpose tool used in IT systems to convert files from one format to another. This file conversion is also a common problem faced in integrating different manufacturing system elements. XSLT is most commonly used to convert files to HTML for display on Web browsers, but it can be used for much more. Unfortunately, XSLT is a difficult language to master, but its power means it may be applied in many different projects. For example, you could use XSLT to convert incompatible recipe, historian, and configuration files between applications. You can use XSLT to convert a single source file with P&ID tags to configuration files for HMI displays, tag lists for OPC data servers, installation checkout files, and maintenance configuration files.

The B2MML-to-SAP XSLT is an example of an information technology tool that was effectively applied to a manufacturing problem. IT tools are important elements when stitching together systems from multiple control vendors, because much of the integration involves data communication and conversion. I recommend adding XSLT to your IT toolkit; you will be surprised at the number of places you can use it.