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Generative AI cannot untangle legacy manufacturing code or satisfy ISA-95 standards without deterministic architecture rules and direct co-design by frontline operators.
AI-assisted summary of OGs in AI: Modernizing Legacy Manufacturing Systems with the Help of AI With FiveTwo — original source. Check the original for full context.
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## Background Published on YouTube by Ai4 on August 24, 2025, this presentation features Glenn Brown, Technical Director at FiveTwo. According to the description, the session explores how a team of experienced technologists combined traditional IT knowledge with modern generative AI to understand, document, and modernize decades-old legacy systems at New Zealand Steel while aligning with ISA-95 automation standards.
## TL;DR FiveTwo partnered with New Zealand Steel to untangle hundreds of thousands of lines of legacy manufacturing code dating back to 1987. Early experiments revealed that naive RAG failed on multi-file business logic and generated code-level jargon instead of operational insights, prompting the team to feed the model structural system topologies and bridge the gap between source code and steelmaking terminology. To evaluate ISA-95 standards compliance, they wrapped generative models within deterministic code and domain rules rather than relying on unguided AI. Ultimately, the project highlighted that successful enterprise adoption depends on addressing frontline mistrust through collaborative co-design and centering the workforce.
## Atmosphere & style The presentation is grounded, humble, and refreshingly candid, balancing self-effacing humor about veteran IT practitioners with pragmatic engineering reality. Glenn delivers an honest narrative arc that takes the audience from initial overconfidence and jarring technical hurdles to genuine cultural breakthroughs on the plant floor. Watching the talk feels like hearing a practical, unhyped war story that champions human craftsmanship and operational empathy over technological panaceas.
## Key takeaways - [00:04](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=4s) New Zealand Steel's Glenbrook facility operates mission-critical production on hundreds of thousands of lines of bespoke legacy code dating back to 1987. - [01:39](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=99s) Basic Retrieval-Augmented Generation (RAG) succeeds on isolated, single-file code questions but fails when business logic is fragmented across multiple modules, tables, and routines. - [03:33](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=213s) Resolving complex cross-file legacy dependencies requires mapping holistic structural relationships, including UI layers, data definitions, and runtime execution order. - [04:20](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=260s) A major semantic gap exists between low-level procedural code execution and the high-level domain terminology used by steelmakers and plant operators. - [06:00](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=360s) Large language models cannot autonomously evaluate industrial benchmarks like the ISA-95 standard without human interpretation and domain-specific grounding. - [06:30](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=390s) Enclosing generative AI models within traditional deterministic code constraints ensures structured, reliable evaluations that prevent hallucinated compliance. - [07:12](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=432s) Enterprise AI rollouts face symmetrical adoption risks: leadership over-optimism treating AI as a panacea, and frontline skepticism fueled by distrust and fear of displacement. - [08:00](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=480s) Successful deployment requires involving frontline domain specialists as co-designers from day one so the tools match operational workflows and foster organizational ownership. - [09:00](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=540s) Technological modernization ultimately hinges on the human element, encapsulated by the Māori proverb 'He tāngata, he tāngata, he tāngata' (it is people).
## Detailed walkthrough ### [00:04](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=4s) A Drive to Glenbrook Steel Mill and Code from 1987
At the beginning of 2023, while ChatGPT was sweeping global headlines, Scott, the CEO of FiveTwo (sitting in the front row of the audience), took a drive down a long country road out to the Glenbrook Steel Mill, the base of New Zealand Steel. New Zealand Steel has a long legacy of technical pioneering, having been the first company in the world to manufacture steel from ironsand, and is currently transitioning to produce environmentally friendly steel. Yet, sitting across from their head of IT, Scott heard a struggle shared by countless mature industrial organizations: "We've got a lot of old systems with a lot of old code. It's going to take forever to update them." Having witnessed modern generative AI's coding capabilities, Scott asked a straightforward question: "What if AI could help?"
Fast forward several months, and the FiveTwo team came face-to-face with the reality of the mill's digital backbone: massive systems running code written as far back as 1987. While it was deeply impressive that these bespoke platforms had successfully kept heavy steel production running for decades, the codebase was staggering. The team found themselves staring down hundreds of thousands of lines of dense, unfamiliar legacy logic that nobody fully understood anymore, wondering if artificial intelligence could genuinely untangle it.
- New Zealand Steel's Glenbrook facility is renowned for pioneering industrial steel production using local ironsand. - The core operational applications contained hundreds of thousands of lines of legacy code dating back to 1987.
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[01:39](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=99s) The First RAG Experiment: Magic Meets Reality
Eager to test the waters, the team launched a rapid experiment. They gathered a collection of source code files, fed them into a Large Language Model (LLM) with prompts to explain the purpose of each file, and ingested those generated summaries into a standard Retrieval-Augmented Generation (RAG) conversational interface. With their hearts pounding, they submitted an initial technical query: "How is minimum slab length calculated?" The response arrived like pure magic—accurate, nuanced, and derived purely from raw source code. Their jaws dropped, leaving them wondering if solving legacy modernization could truly be that effortless.
The euphoria vanished with their next question: "How are customer orders matched up to materials?" The tool scanned the codebase, attempted an answer, and failed miserably. The team slumped in their chairs. When dissecting the failure, the underlying reason became clear: the naive RAG architecture worked brilliantly whenever an answer was self-contained within a few neat, cohesive files. However, whenever business logic was fragmented across separate modules, data tables, and background routines, the LLM had no inherent concept of how those disparate pieces connected or interacted.
```mermaid flowchart TD accTitle: Naive RAG vs Structured Legacy Understanding accDescription: Flowchart contrasting simple document-level retrieval with structural orchestration for legacy codebase queries.
subgraph Naive["Initial Naive Approach"] A["Code Files (1987)"] --> B["LLM File Summaries"] B --> C["Basic RAG Search"] C --> D{"Information Scope"} D -->|"Contained in single file"| E["Success (e.g., Slab Length)"] D -->|"Scattered across files"| F["Failure (e.g., Order Matching)"] end
subgraph Contextual["Structural Approach"] G["UI, Data, & Code Files"] --> H["Execution Order & Call Hierarchy"] H --> I["Legacy System Architecture Map"] I --> J["Cross-File Semantic Reasoning"] end ```
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[03:33](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=213s) Bridging the Semantic Gap: Structure and Steelmaking Know-How
To fix the structural blindness, FiveTwo taught the model the broader system topology. They fed it the user interface layers, data definitions, auxiliary code files, and most importantly, the execution order and dependencies binding the system together. Glenn noted with self-deprecating humor that it helped that their team members are "kind of old and legacy ourselves," making the quirks of 1980s software architecture feel intimately familiar. With system architecture explicitly mapped, the tool finally began resolving queries spanning multiple interacting files.
Yet another hurdle immediately surfaced. Confident in the new setup, the team asked: "In the hot mills, how is the initial slab lineup formed?" Instead of an operational summary, the model produced pages and pages of exhaustive, line-by-line code traces. The system was functioning purely at the weeds level of syntax and subroutines. Real steelmakers do not think in execution stacks; they think in operational concepts like hot rolling, lineups, and metallurgy. The legacy code itself contained no explicit labels for terms like "hot mill" or "slab lineup." The breakthrough occurred when the team engineered an interpretive bridge connecting low-level procedural source code to the practical domain know-how of veteran steelmakers, finally yielding answers tailored to human operational needs.
- Effective retrieval required teaching the model structural relationships: user interfaces, data definitions, and runtime execution sequences. - An ontology gap existed between low-level code instructions and the high-level business concepts used by plant operators.
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[06:00](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=360s) Aligning with ISA-95: Why Reading the Standard Matters
The necessity of grounding AI in human expertise became even clearer during a parallel initiative: auditing New Zealand Steel's operations against ISA-95, the international benchmark for integrating enterprise management systems with industrial control and manufacturing execution systems (MES). The team initially tested whether an LLM could evaluate compliance autonomously. Glenn delivered the spoiler: "It couldn't. At least not by itself."
Rather than trusting an unguided model to hallucinate standards compliance, the FiveTwo team took a step back and did something "pretty drastic": they sat down and physically read the ISA-95 specification cover-to-cover to understand how it operates in real-world manufacturing environments. They then wrote traditional, deterministic code to establish constraints and programmatic workflows, enforcing how the LLM should interpret and evaluate the systems against the standard. Wrapping the generative capabilities in deterministic rules and domain context transformed chaotic output into structured, reliable compliance evaluations.
- Raw LLMs struggle to correctly apply industrial frameworks like ISA-95 without explicit scaffolding. - Combining generative models with traditional procedural programming guarantees strict alignment with formal standards.
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[07:12](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=432s) The Human Element: Overcoming Distrust and the Wisdom of He Tāngata
When FiveTwo brought their new toolset to the mill's operational teams expecting applause, the reception was lukewarm at best—a collective "meh." Users complained that the outputs were too long-winded or failed to use their specific department's insider shorthand. Glenn tried steering the room toward collaborative iteration, saying, "Let's dive into that feedback. That's exactly what we need." His invitation was met with dead silence until one team member voiced the underlying reality: "I don't trust AI."
That moment exposed the broader organizational fracture common to AI transformations. Frontline employees often mistrust the technology, lack guidance on how to apply it, or harbor deep fears that automated systems will replace their jobs and strip them of purpose. Conversely, executive leaders often mistake AI for an all-powerful silver bullet. Both extremes can derail a deployment. Reflecting across customer engagements, FiveTwo realized the only projects that succeeded were those where frontline operators were engaged as co-designers from day one, contributing their domain wisdom and witnessing how the tooling served their everyday workflow. Glenn concluded by reciting a renowned Māori proverb:
> *"He aha te mea nui o te ao? He tāngata, he tāngata, he tāngata."* > ("What is the most important thing in the world? It is people, it is people, it is people.")
- Frontline skepticism ("I don't trust AI") and executive over-optimism are symmetrical threats to enterprise AI adoption. - Real adoption requires continuous co-design where frontline specialists contribute their expertise and develop ownership over the tooling. - The presentation closed with an open invitation for attendees to visit booth K17 to discuss legacy transformation or reminisce about old-school IT.
## Notable quotes > [00:04](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=4s) We've got a lot of old systems with a lot of old code. It's going to take forever to update them. — Head of IT at New Zealand Steel
> [00:04](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=4s) What if AI could help? — Scott
> [01:39](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=99s) How is minimum slab length calculated?
> [01:39](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=99s) How are customer orders matched up to materials?
> [03:33](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=213s) kind of old and legacy ourselves — Glenn Brown
> [03:33](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=213s) In the hot mills, how is the initial slab lineup formed?
> [06:00](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=360s) It couldn't. At least not by itself. — Glenn Brown
> [07:12](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=432s) Let's dive into that feedback. That's exactly what we need. — Glenn Brown
> [07:12](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=432s) I don't trust AI. — Team member
> [07:12](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=432s) He aha te mea nui o te ao? He tāngata, he tāngata, he tāngata. — Glenn Brown
> [07:12](https://www.youtube.com/watch?v=dgt8eWqM4R4&t=432s) What is the most important thing in the world? It is people, it is people, it is people. — Glenn Brown
## Mentioned Ai4, Glenn Brown, FiveTwo, Scott, New Zealand Steel, BlueScope, Glenbrook Steel Mill, ChatGPT, ISA-95, Retrieval-Augmented Generation (RAG), Large Language Models (LLMs), Manufacturing Execution Systems (MES)
## Video description Glenn Brown, Technical Director, FiveTwo
Abstracts
What happens when a bunch of Gen Xers apply AI to heavy industry? In our talk, we’ll tell you our story. We’ll share how we combined old-school IT and modern GenAI to help understand and update aging steel manufacturing systems – and align with international standards for automation (ISA-95). New Zealand Steel, a BlueScope company, was the first in the world to manufacture steel from ironsand. Yet even with such innovation at its core, it faced an all-too-common problem as time went by: the bespoke IT systems running its operations were aging. So were the people who understood those systems best. Having worked with such systems back in the day, we knew just how messy and unstructured they could be by today's standards. But through our recent work and research, we knew that modern generative AI could help make sense of these older systems – as long as we gave it the right support. We’ll show how we used AI to help understand and document a range of legacy applications, prepare those systems for replacement, and be guided by applicable standards. The use of AI can potentially save several million dollars over the course of a project. It can also drastically cut the time required, enabling deep analyses within hours that might otherwise take months.
[Source](https://www.youtube.com/watch?v=dgt8eWqM4R4)