UMDA standards notes
ISA-95 is the standard for connecting enterprise systems to manufacturing operations. Its object model gives a site shared nouns: what equipment is, what a material lot is, what a work order is. In the UMDA's division of labor, ISA-95 answers the where, the who, and the what of production; its companion ISA-88 answers the why, the how, and the when. These notes define the objects the way practitioners use them. For the normative text, buy the standard from ISA. For the framework that puts these objects to work, see the Unified Manufacturing Data Architecture.
Each object below has a stable anchor. Tools in the UMDA toolset link here from their exports, for example an RDF ontology whose Batch class points at its ISA lineage via rdfs:seeAlso. If a link brought you to this page, the highlighted heading is the object your model descends from.
Every box is defined on this page; select one to jump to its definition. Solid arrows are structure ("a material has lots, a lot splits into sublots"), dashed lines are associations. The labels on the lines carry the meaning, so the map reads without color.
isa95:EquipmentA defined piece of the plant with a role in operations: a site, an area, a line, a work cell, a unit, a tank. Equipment is the role, not the serial number. A filler position on line 3 is equipment. The specific machine bolted there this year is a physical asset.
Equipment forms a hierarchy, and that hierarchy is the spine most site models hang from. When people argue about naming topics in a UNS, they are usually arguing about the equipment hierarchy. The named levels of that hierarchy, enterprise down to work unit, each get their own object below.
isa95:EquipmentClassA grouping of equipment that shares properties: all blenders, all tablet presses, all pasteurizers. Classes are where shared capabilities and shared property definitions live, so a model does not repeat itself once per machine.
isa95:EnterpriseThe top of the equipment hierarchy: the company or operating group that decides what gets made and where. Product portfolios, capital, and standards live here. It is the level that speaks ERP.
isa95:SiteA physical place that makes things: the plant. Sites are where planning gets real. The enterprise plans a product family; a site commits to producing this much of it. Most UNS namespaces put the site right after the enterprise for exactly this reason.
isa95:AreaA functional region inside a site: granulation, packaging, utilities, the warehouse. Areas group the work centers below them, and the good ones match how supervision and accountability are actually divided on the floor.
isa95:WorkCenterThe level where production capacity lives. ISA-95 names its specializations: a process cell in batch, a production line in discrete, a production unit in continuous, a storage zone in the warehouse. Work center is the umbrella over all four, and it is the level scheduling thinks in.
isa95:WorkUnitThe smallest element inside a work center that does work on its own: the unit in a process cell, the work cell on a line, the storage unit in a zone. Where ISA-88's unit runs the batch, ISA-95's work unit is the same idea generalized to every kind of production.
isa95:MaterialWhat a thing is, not a quantity of it. The material master entry: an API, an excipient, a packaging component, a finished good. One material definition, many lots of it. If it has a stock number, it is probably a material definition.
isa95:MaterialClassA grouping of material definitions that share handling and rules: all solvents, all films, all finished goods of one family. Specifications and policies attach to the class, so a new material inherits its family's rules instead of restating them.
isa95:MaterialLotA real quantity of one material that shares an identity and a quality status. The lot number on the label. Lots are where genealogy lives: which lots went into which batches, and which lots came out. When a recall happens, the question is asked in lots.
isa95:MaterialSublotA physically separate part of a lot: a pallet, a container, a drum, or a single serialized unit. Every sublot belongs to exactly one lot and inherits its quality status. Serialization work in discrete manufacturing usually models serial numbers as sublots.
isa95:PersonnelThe people side of operations: individual persons and classes of persons, with the qualifications and certifications that decide who may run what. When a batch record says a qualified operator signed a step, personnel objects are what makes qualified checkable.
isa95:PersonnelClassA grouping of persons who share qualifications: certified welders, line 3 operators, qualified reviewers. Requirements attach to the class and people prove membership, which turns "a qualified operator signed this" from a hope into a checkable statement.
isa95:PhysicalAssetThe serialized physical thing: the machine with the asset tag, the one maintenance actually wrenches on. The pairing with equipment matters. Equipment is the role, the physical asset is the occupant, and the mapping between them changes when machines get swapped. Sites that merge the two regret it during the first major overhaul.
isa95:ProcessSegmentA step of production seen from the business: what personnel, equipment, and material capabilities it takes to do a chunk of work, at the level of detail the business plans and costs. Mixing, filling, and packing might each be a segment. Segments are the vocabulary that scheduling and costing share with the shop floor.
isa95:OperationsDefinitionHow to make a product, in operations terms: the segments it takes, in what order, with what resources. It is the operations counterpart of a bill of process. Where ISA-88 has a recipe for a batch, ISA-95 has an operations definition for any kind of work, including work that is not batch at all.
isa95:OperationsScheduleA set of operations requests laid out over time: the plan. Schedules come down from planning systems, get negotiated against reality, and go back up as performance. A schedule is a container; the individual instructions inside it are requests.
isa95:OperationsRequestOne instruction to do work: make this much of that product by then. In everyday language, the work order. Requests are the handshake between the enterprise and the site, which makes them one of the most integrated and most argued about objects in the whole model.
isa95:JobOrderThe dispatch-level instruction: one request broken into the pieces a work center executes now. Where the operations request speaks for the enterprise, job orders speak to the line. An MES dispatch list is a list of job orders.
isa95:OperationsPerformanceWhat actually happened: the response to a request. Quantities produced and consumed, equipment used, people involved, time taken. Performance is where the record of production lives, and it is the raw material of every OEE number anyone has ever disputed.
isa95:WorkMasterThe detailed, executable work definition at the operations level: the template the MES actually runs, with steps, parameters, and data collection points. An operations definition says what it takes; a work master says exactly how it runs. In batch plants the work master and the ISA-88 control recipe are close cousins.
Companion page: ISA-88 objects in plain language. See how these objects translate to OPC UA, MQTT/Sparkplug B, B2MML and more in the Standards Crosswalk, or model them and export schemas with the Common Data Model Designer.
Part of the UMDA standards notes and the UMDA toolset. ISA-95 is a standard of the International Society of Automation; these plain language notes are not a substitute for the normative text. The Unified Manufacturing Data Architecture is described at umda.info. Notes © 2026 Unified Manufacturing Data Architecture. All rights reserved.