XML Used for STEP Process Data

by
William G. Beazley, PhD
Information Assets, Inc.

The trend in E&C firms has always been to integrate applications by sharing or reusing data. However, in the rapidly mobilized and demobilized design organizations of today, with the problems discussed, full integration with trading partners or even certain internal resources is usually too slow and costly to attempt to any great degree.

Hence it often more practical to interface applications using transactions. In the process industry, as well as others, there have been several initiatives to develop formats to pass data, Including:

IGES,

STEP,

EDI, etc.

Importantly, many of these initiatives have been less that successful but their data dictionaries and data models remain available to us to resuse.

Why XML?

XML (Extensible Markup Language) is the second application of SGML (Standard Generalized Markup Language) to be developed for use on the WWW. The first, HTML (Hypertext Markup Language) is the well know tag language for marking text for presentation as web pages. While HTML structures documents for presentation, XML (as does SGML) structures documents for content. The simplifications introduced in XML make it much easier to design, program and use than the more generalized SGML.

For example, as simple XML file might contain:

<Name>Bill Beazley</Name>

</Contact>

Here content is identified by easily readable tags.

Like SGML, XML can use a Document Type Definition (DTD) to describe how to structure a document. For a number of reasons, there are efforts now underway to define XML schemas in better ways that a DTD. For example, DTD’s do not use the XML format and they cannot easily specify the data type between tags.

The DTD for the above would contain:

<!ELEMENT Contact - - (Name, Phone)>

<!ELEMENT Name - - CDATA>

<!ELEMENT Phone - - CDATA>

Here "Contact" contains "Name" and "Phone".

The characteristics making XML attractive as an interfacing transaction :

· Readable Structure. The human-readable tags allows domain experts to examine and assure data integrity without special software applications.

· Ubiquitous Interface. The widespread support building for XML among browsers, databases, authoring tools and other content applications reduces the cost and risk of extending applications to input and output XML.

· Convert to HTML using XSL. Using Extensible Stylesheet Language (XSL), XML can be converted to HTML for browser display.

· DOM. Elements and Attributes of the XML document can be directly accessed and manipulated using the Document Object Model (DOM)

· HTTP Compatible. XML files are retrieved using normal HTTP (Hypertext Transfer Protocol) requests. And since the files are transferred as ASCII characters, XML poses no virus hazards.

XML in Plant Design

Thus the business case for XML in plant design depends largely on finding industry transactions that benefit from being done on the WWW. Process Delivery. The Process Data Exchange Institute (pdXi), initiated in 1989 by AIChE's Computing and Systems Technology Division, establishes written protocols and specifications for the exchange or process engineering data among computer programs, databases, and organizations within process engineering.

PdXi is developing an XML implementation of their STEP Application Protocol for process data exchange (ISO 10303 AP 231).

For more information, contact: Tom Teague, pdXi Technical Director, Protesoft Corporation, 10400 S. Post Oak Rd., Suite E-PMB#300, Houston, TX 77035, Telephone: 713-728-9140, Fax: 713-728-1371, E-mail: info@protesoft.com, or consult: http://www.aiche.org/industry/pdxi/.

The Future

Clearly there are transactions that lend themselves to XML's advantages in plant design. Many vendors, such as Bentley, SAP, IBM, Oracle have announced XML support from their product

The bigger vendors, such as, Microsoft, IBM, SUN, as well as a host of smaller vendors are betting that there is money to be made in selling "content servers" to process and format content in XML and related formats. Microsoft and Corel have already committed to XML support in their office suites (Corel has support SGML for years). XML data transfer and applications interfacing look the right idea at the right time.

More Information

For more information, contact: William G. Beazley, PhD, President, Information Assets, Inc., 5700 Northwest Central Dr., Suite 160, Houston, TX 77092, TEL: 713-690-7644, FAX 713-690-7645, email: wbeazley@infoassets.com.