SCADA operates in real time at ISA-95 Levels 1 and 2, communicating with PLCs. MES sits at Level 3, managing production orders, scheduling, genealogy, performance and the connection to business systems at Level 4.
ISA-95 sets the functional levels and the object models. The MESA model describes the MES function set. B2MML provides the XML schema for moving production orders and results between MES and ERP without bespoke point-to-point coding.
For many Australian food sites a well-structured SCADA historian with order data from ERP covers the need. Full MES becomes justified when recipe management, lot genealogy, scheduling complexity or electronic batch records exceed what ERP and SCADA handle cleanly.
MES and SCADA are the two systems most commonly confused in food manufacturing conversations. The confusion is understandable. Both deal with production data, both are often displayed on similar screens, and modern platforms have made the boundary between them less obvious than it used to be.
Understanding what each system actually does, where the integration between them matters, and which published standards govern that integration is useful before deciding what you need. This article sets out the ISA-95 functional levels, the MESA functional model, the B2MML data exchange, the SCADA-to-MES boundary, and a worked Level 2 to Level 3 data mapping that shows how plant data becomes a contextualised production record.
This post supports our systems integration work, where the connection between control systems, MES and ERP is designed and delivered.
SCADA is a control and monitoring system. It runs in real time, communicating with PLCs to read process values, display plant state on operator interfaces, manage alarms, and in many cases execute control actions directly. SCADA is the system the control room operator uses to see what the plant is doing and to intervene when something needs attention. This is the layer covered by our PLC, SCADA and HMI work.
A SCADA historian records time-series data: temperatures, pressures, flow rates, line speeds and equipment states. That data is accurate and granular, but it captures what happened at the process level, not what was being produced or why. A historian tag will tell you that a filler ran at 480 units per minute between 14:02 and 14:37; it does not, on its own, tell you that the run was work order 10455 producing a 600 mL SKU against recipe version 3.
MES sits above the control system. It manages the relationship between production orders, from ERP or planning, and what the plant floor actually does. The Manufacturing Enterprise Solutions Association (MESA) describes the function set an MES typically covers, and the core functions in a food plant are these.
These functions are what turn raw process data into a production record that operations, quality and the business can act on.
ISA-95, published jointly as ANSI/ISA-95 and as IEC 62264, is the international standard for integrating enterprise and control systems. It provides the framework for understanding where SCADA and MES sit relative to each other and to the broader enterprise. The standard, maintained through the ISA's ISA95 committee, defines a functional hierarchy.
| Level | System | Function | Time domain |
|---|---|---|---|
| Level 0 | Field devices | Sensors, actuators, the physical process | Continuous |
| Level 1 | PLC, control | Sensing and manipulating the process | Milliseconds to seconds |
| Level 2 | SCADA, HMI | Supervisory control and monitoring | Seconds to minutes |
| Level 3 | MES | Production management, genealogy, scheduling, OEE | Shifts, days |
| Level 4 | ERP | Business planning, procurement, financials | Days, weeks, months |
The integration between Level 3 and Level 4 is where production orders flow down from ERP to MES, and where actual production results flow back up. The integration between Level 2 and Level 3 is where SCADA provides process data to MES, and where MES sends recipe parameters and order context down to the control system. ISA-95 also defines the object models that cross these boundaries, including the production schedule, the production performance record, the material definition and the material lot. Specifying an MES integration against these named objects is more durable than describing it informally.
The boundary between SCADA and MES is functional, not always architectural. The clearest way to define it is by what each layer owns.
SCADA owns the real-time picture: live values, alarms, operator control actions, and the high-resolution historian. Its job is correctness and responsiveness now. MES owns the production context: the work order, the recipe version, the material lots, the people, and the assembled batch record. Its job is to make the process evidence meaningful and auditable after the fact.
That boundary has blurred because platforms now span it. Modern SCADA products carry MES-grade modules, for example an ISA-88 batch engine, OEE and recipe management running on the same database and tag model as the supervisory layer. A dedicated MES, conversely, can reach down to acquire plant data directly. The result is that one product may implement functions on both sides of the line. The boundary still exists as a design concept even when a single platform straddles it, because Level 2 questions ("is the process correct right now?") and Level 3 questions ("what did we make, from what, against which order?") are answered differently and serve different users.
Two industry references make the Level 3 layer and its integration concrete.
The MESA model describes the functional scope of MES: resource allocation and status, operations and detailed scheduling, dispatching production units, document control, data collection and acquisition, labour management, quality management, process management, maintenance management, product tracking and genealogy, and performance analysis. Where ISA-95 tells you where MES sits and what crosses its boundaries, the MESA model tells you what MES does inside that boundary. Reading a tender or a vendor proposal against the MESA function list is a quick way to see which functions are genuinely included and which are stubs.
B2MML, Business to Manufacturing Markup Language, is a set of XML schemas published by MESA that implement the ISA-95 object models. It gives MES and ERP a common, standards-based format for exchanging production schedules, production performance, material definitions and personnel data. Using B2MML rather than a bespoke point-to-point interface means the integration is documented against a published standard, is easier to extend when a new object is added, and is less fragile when one system is upgraded. For a food plant connecting MES to an ERP, B2MML is the structured alternative to a hand-coded flat-file or database interface. Where a B2MML interface is not warranted, the same ISA-95 object definitions can still discipline a simpler interface so that both ends agree on what a "production performance" message contains.
Contextualisation is the step that turns SCADA data into an MES record. A historian tag is a value with a timestamp. An MES record is that value bound to an order, a product, a recipe version, a material lot and a person. Contextualisation is the binding work, and it is where most of the integration effort lives.
The mechanics are: a stable tag model in SCADA so the same physical measurement always maps to the same address; a time base shared between SCADA and MES so events align; and a contextualisation rule that says, in effect, "while work order X is active on line Y, attribute these tags to this order." Get the tag model and the time base wrong and the contextualisation produces records that look complete but attribute data to the wrong order. This is one reason a disciplined tag and User Defined Type model in SCADA pays back directly at the MES layer.
Consider a typical dairy filling line as an illustration. The numbers and tag names below are illustrative and used only to show the shape of the mapping; they are not a Metromotion Controls measurement or a client result.
Suppose the SCADA layer (Level 2) exposes these historian tags for the filler:
Line3/Filler/Count_Total integer, units produced (cumulative)
Line3/Filler/Speed_Actual real, units per minute
Line3/Filler/State enum: Running / Idle / Faulted / Changeover
Line3/Filler/Reject_Count integer, units rejected at checkweigher
Line3/CIP/Temp_Return real, degrees C
Line3/CIP/Conductivity real, mS/cmThe MES layer (Level 3) holds the order context for the run:
WorkOrder 10455
Product 600 mL whole milk, SKU 6012
RecipeVersion 3
Line Line 3
PlannedQty 24000 units
MaterialLots [milk silo 2 lot M-2207, caps lot C-1144]
Operators [shift B]The Level 2 to Level 3 mapping binds them. While work order 10455 is the active order on Line 3, MES attributes the filler tags to that order and derives the production record.
| Level 2 source (SCADA) | Contextualisation rule | Level 3 result (MES) |
|---|---|---|
Count_Total delta over the run | Attribute to active work order while State = Running | Good count for WO 10455 |
Reject_Count delta | Same window, classified as quality loss | Quality loss for OEE |
State time in Running vs Faulted/Changeover | Availability calculation against planned run time | Availability loss for OEE |
Speed_Actual vs rated speed | Performance against ideal cycle | Performance loss for OEE |
CIP/Temp_Return, CIP/Conductivity over the wash | Captured to the CIP cycle preceding the run | CIP evidence attached to batch record |
MaterialLots (from order release) | Bound at order start | Genealogy: lots M-2207 and C-1144 linked to finished lot |
For example, if the line runs 50 minutes against a 60 minute planned window, fills 22,800 good units and rejects 360, and the rated speed is 500 units per minute, then availability is roughly 83 percent, performance is the actual rate against rated, and quality is about 98.4 percent. MES multiplies the three into an OEE figure attributed to work order 10455 rather than to an anonymous time block, and the genealogy record ties finished lot to milk lot M-2207 and cap lot C-1144. That attribution is the entire point of the Level 2 to Level 3 integration: the same raw counts become a defensible, order-level production and traceability record. The limits of OEE as a single number are worth understanding before reporting it widely, which we cover in our note on OEE limitations.
For many Australian food sites, particularly single-product or limited-SKU operations, a well-structured SCADA historian with order-level data from ERP covers the practical need. A dedicated MES earns its cost when the following signals appear.
A practical sequence is to map the required Level 3 functions against the MESA model, check which the existing SCADA and ERP already cover, and scope MES only for the genuine gap. Buying a full MES to obtain one or two functions that SCADA could carry is a common and avoidable over-spend. The reverse error, forcing complex genealogy and scheduling into a historian and a spreadsheet, is just as costly in audit and recall exposure.
Australian food and beverage manufacturers operate under the FSANZ Food Standards Code and customer and retailer traceability expectations that, in practice, require lot-level genealogy and defensible batch records. The genealogy and quality functions in the MESA model map directly onto those obligations, which is often what tips a multi-SKU site towards a dedicated MES rather than a historian alone.
Many Australian sites also run mixed PLC estates and a mix of legacy and modern SCADA, so the Level 2 to Level 3 integration has to accommodate more than one control platform. A consistent tag model and a standards-based ERP interface matter more in that environment, because the contextualisation layer is bridging several systems rather than one. Sites in the food and beverage and dairy sectors typically have the SKU range, allergen sequencing and recall exposure that make the Level 3 functions worth formalising. A recurring blocker is fragmented plant data spread across disconnected systems, which we cover in breaking down plant data silos; the MES contextualisation layer is one of the main tools for resolving it.
The distinction between MES and SCADA is functional, defined by the ISA-95 levels, described by the MESA model, and made portable by B2MML and the ISA-95 object models. SCADA manages the real-time control environment at Levels 1 and 2; MES manages the production management layer at Level 3; ERP plans the business at Level 4. The integration between them, especially the Level 2 to Level 3 contextualisation shown in the worked example, is where food manufacturers create the batch records, genealogy linkages and order-level performance reporting that auditors, customers and operations teams rely on. The right starting point is to map the functions you actually need against the standard, confirm what your existing SCADA and ERP already cover, and scope only the genuine gap.
The standards and model references above are general industry sources, cited so the technical claims can be checked against the originals. They are not Metromotion Controls measurements.
Tommy Kim writes for Metromotion Controls, a Melbourne control systems integrator delivering PLC, SCADA, controls integration and commissioning for food, beverage, dairy and FMCG manufacturers across Australia.
ISA-95, published jointly as ANSI/ISA-95 and IEC 62264, is the international standard for integrating enterprise and control systems. It defines a functional hierarchy from Level 0 field devices up to Level 4 business planning, and it defines the object models, such as production schedule, production performance and material lot, that move between those levels. MES sits at Level 3, between the control systems below and ERP above. SCADA sits at Levels 1 and 2. The standard is useful because it gives a common vocabulary for specifying exactly what data an MES integration should exchange with SCADA below it and ERP above it.
The MESA model, from the Manufacturing Enterprise Solutions Association, describes the functions an MES performs, such as resource allocation, scheduling, dispatching production, document control, data collection, labour management, quality management, process management, maintenance management, product tracking and genealogy, and performance analysis. Where ISA-95 defines the levels and the data exchanged between them, the MESA model defines the functional scope of the Level 3 layer itself. The two are complementary: ISA-95 tells you where MES sits and what crosses its boundaries, and the MESA model tells you what MES does inside that boundary.
B2MML, Business to Manufacturing Markup Language, is a set of XML schemas published by MESA that implement the ISA-95 object models. It gives MES and ERP a common, standards-based format for exchanging production schedules, production performance, material definitions and personnel data. Using B2MML rather than a bespoke point-to-point interface means the integration is documented against a published standard, is easier to extend when a new object is added, and is less fragile when one system is upgraded. For a food plant connecting an MES to an ERP such as SAP or a mid-market system, B2MML is the structured alternative to a hand-coded flat-file or database interface.
SCADA can replace some MES functions, particularly in simpler operations. Modern SCADA platforms with an integrated historian, batch management and reporting can cover production tracking, OEE and basic traceability. Functions higher in the MESA model, such as finite scheduling, full material genealogy, labour management and integrated quality management with hold and release, typically need a dedicated MES. The boundary is functional rather than fixed: where the SCADA platform carries MES-grade modules, the same product can span both layers, but the Level 3 functions still have to be designed and not assumed.
A SCADA batch record captures the process data for a batch: temperatures, times, alarm events and operator actions within the control system. An MES batch record adds the production context: which work order, which recipe version, which raw material lots were consumed, which operators signed off and the quality results. The MES record is the one used for regulatory compliance, customer audits and recall, because it links the process evidence to the order, the materials and the people. SCADA produces the raw evidence; MES assembles it into a defensible, contextualised record.
SCADA can calculate OEE for a time period from machine states and counts it reads from the PLC. MES calculates OEE against the production order, attributing availability loss, performance loss and quality loss to a specific job, product and shift, and reconciling it with the schedule and the genealogy record. The MES view is more useful for operations decisions because losses are tied to what was being made and why, not just to a clock window. The quality of either figure depends on machine states being read directly from the control layer rather than entered by operators.
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