ISA-95 Implementation Best Practices: Production Models and Segments

ISA-95 and Business-to-Manufacturing Markup Language (B2MML), like any standards, are subject to interpretation.

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Manufacturing execution systems (MES) and enterprise resource planning (ERP) systems vendors could interpret these standards differently, which could result in variants of the implementations, thus leading to interoperability issues.
B2MML Applications illustrate: how Parts 1 and 2 of ISA-95 (promulgated by the Instrumentation, Systems and Automation Society) are applied to a usable eXtensible Markup Language (XML)-based infrastructure; data mappings; description of the schema choices; how B2MML has been used; and how B2MML is evolving to support extensions and a broader range of transactions. Workflows illustrate how ISA-95 Parts 3 and 5 are applied to describe workflows between B2MML applications and ERP Systems in typical manufacturing operations activities.

Considering Production Models

 Agile production models require more transactions and more complex data to be exchanged between Enterprise and Control Systems, as shown above. The interactions between enterprise activities and control activities become more complex when considering the different production models: Make to Stock, Make to Order and Engineer to Order.
Engineer to Order is probably the most demanding integration. Information Exchange is synchronous and more in near time. The aerospace industry offers one of the best examples. Products are designed and engineered to drive the planning, but these definitions could change during execution.

In Engineer to Order, change requests might be sent back to engineering/planning, which puts the execution on hold waiting for the changes to be reflected in planning. A new set of operations or a variation on the route (i.e. in case of added inspections) will then be communicated to the shop floor to complete the work orders.

Additionally, messages are richer in content and require a significant amount of extensions to B2MML. Performance Reports contain as-designed and as-built data.

Another key concept to understand is the use of Segments in the B2MML schemas. A Segment is a functional unit of integration and defines the content model for information interchange.

As noted by Charlie Gifford, director of lean production management at GE Fanuc Intelligent Platforms, in Charlottesville, Va.: “The 95 object models and resulting B2MML schemas are based on the construction of a ‘Segment,’ or unit of work, which is the ISA-95 term for an operation. It is the foundation concept of the ISA-95 data model. A Segment in a recipe or production route is constructed by using the personnel, equipment and materials models in unison to describe the unit of work in terms of resources and resource test requirements.”

A Process Segment defines those plant capabilities used to execute production. Those Segments are ultimately used to create Product Segments (i.e. production routes or control recipes), which make up the actual product. Segments are recursive structure, in the sense that they can nest other segments. This recursion allows different applications to access the information needed depending on the relative context.

For example, a scheduling application might only be initially interested in a high-level Bill of Resources to execute a give work order. On the other hand, a dispatching solution will need to retrieve the underlying sequence of Segments that define the different steps of a production route. This powerful mechanism is especially convenient when the data needs to be re-aggregated into a Production Performance document or message to be reported for analysis, tracking and the like.

The modular nature of the Segments avoids the need for complex custom filtering and allows different applications to merely map each other’s information.

Lastly, the key to defining the information aspects of manufacturing operations is capturing the context and content of data that needs to be exchanged; this is what gets defined as B2MML Applications, in conjunction with the transaction models defined in ISA-95 Part 5, to provide a basis for describing workflows.

Costantino Pipero, cos@beeond.net, is Chief Executive Officer of Beeond Inc, and Kishen Manjunath,
kishen.manjunath@honeywell.com, is Solutions Architect at Honeywell Process Solutions. This article is excerpted from the MESA white paper, “ISA-95 Implementation Best Practices: Workflow Descriptions Using B2MML.” For more information on MESA, visit www.mesa.org.

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