Explainer
IETM Levels and Classes, Explained
The Origin
A 1994 Navy Paper, Still Quoted
New to the term? Start with what an IETM is, and how it differs from an IETP. This piece is about the scale people use to grade them.
The classes come from “DoD Classes of Electronic Technical Manuals” by Eric L. Jorgensen of the Carderock Division, Naval Surface Warfare Center. Several versions circulated in the early 1990s; the one dated 5 April 1994 was reviewed by the Tri-Service Working Group for IETMs, which approved it for DoD-wide use with a proviso worth remembering: it was to be used for definition only, and not as a specification for procurement.
The paper was written to sort out a crowded field. Programs were buying very different things under the same name, from scanned page viewers to purpose-built interactive systems, and the classes gave them a shared vocabulary. Class 4 was the class the November 1992 DoD IETM specifications (MIL-M-87268, MIL-D-87269, and MIL-Q-87270) were written to deliver.
The Scale
Class 0 Through Class 5
The paper numbers its classes from 0, and you will see them written as Class 1 to 5, Class I to V, or Level 1 to 5. In plain terms:
- Class 0: Non-electronically indexed page images
- Scanned or digital pages kept for archiving or print on demand, with no index for using them on screen. The paper itself says this is not an electronic technical manual at all.
- Class 1: Electronically indexed page images
- Full page images, viewed whole, with an intelligent index for finding the right page. The printed page stays intact. Think of a well-indexed PDF of the paper manual.
- Class 2: Electronic scrolling documents
- Text converted from the page-oriented manual with hypertext links added, displayed as scrolling text. Little or no reauthoring, and very limited navigation written by an author.
- Class 3: Linearly structured IETMs
- The manual is reauthored and tagged to the IETM data definitions as far as possible, then shown through dialog boxes and a content-driven logical Next. Still one linear document underneath, not a database.
- Class 4: Hierarchically structured IETMs
- Content authored into, and maintained in, a non-redundant database of data elements, attributes, and links, then packaged into a run-time version for interactive display. The class the 1992 DoD IETM specifications were written for.
- Class 5: Integrated database systems
- Class 4 content integrated with other processes in the same database, such as expert-system rules, diagnostics, or computer-managed training. In 1994 the paper said it could only be loosely defined.
The Dividing Line
The Data Decides the Class, Not the Screen
The most useful idea in the paper is easy to miss. It says the criteria that separate the classes are not the look of the display but the structure of the data underneath and the work needed to prepare it. At the screen, Classes 3, 4, and 5 can show almost identical features. Underneath, a Class 3 manual is still one linear document, while a Class 4 manual is a managed database compiled for display.
The paper groups the classes in three pairs: 0 and 1 are page flippers, 2 and 3 are scrolling hypertext, 4 and 5 are interactive databases. Moving within a pair is incremental. Moving from Class 3 to Class 4 is the expensive step: it needs extensive reauthoring or conversion by subject matter experts, and most likely revalidation of the manual.
That is why a demo cannot tell you the class. Two viewers can look the same in a sales meeting while one of them will need its content rebuilt the first time the hardware changes.
Level 4
What a Level 4 Deliverable Actually Is
Read against the paper, a Level 4 requirement means four things are being delivered, not one:
- Source data, authored as data elements with attributes and links in a managed, non-redundant store, not as a document.
- A run-time package compiled from that data for the display system.
- Interactive behavior: dialogs, links, and a logical next step driven by the content.
- A way to maintain it as data across configurations and the life of the equipment.
Most disputes over Level 4 come from a buyer who meant all four and a supplier who priced the second and third. In India, where the requirement is usually written as Level 1 to 5 and attributed to Joint Services Guide JSG 0852 (2001), the risk is sharper: we have not found the guide's official text published, and the level descriptions in circulation do not all agree with the 1994 paper or with each other. Some describe Level 1 as any PDF. Whichever document a contract cites, ask for its definition in writing before you price the work.
Today's Standards
Where the Classes Sit Now
For U.S. Army manuals, the governing standard is MIL-STD-40051E (Revision E, March 2025), a single standard for all technical manuals whether they are delivered as electronic or interactive electronic manuals. The Army also fields one viewer for them, IADS, so “Level 4” in an Army context usually means “behaves correctly in IADS”.
S1000D calls the result an interactive electronic technical publication, or IETP. What an IETP must do with applicability, publication modules, and process data modules is decided by the project and its viewer. The Air Force's Enterprise IETM request for information points the same way: its published language names S1000D, the Air Force's MIL-STD-3048 business rules, and a government-owned common source database.
The class scale has not disappeared, though. It survives as shorthand in solicitations, capability statements, and conversations, especially where a buyer wants to say “interactive, properly” in two words.
For Buyers
Specify Behavior, Not a Number
The paper's own authors asked that it not be used as a procurement specification. Take them at their word. Name the standard, then write down the behaviors you are paying for:
- Applicability
- Steps, parts, and illustrations filter to the configuration in front of the maintainer, and the contract says which configuration data drives the filter.
- Links that do work
- Procedures link to the parts, tools, consumables, and fault information they reference, and every link is checked before delivery.
- Fault isolation
- Troubleshooting runs as a dialog, question by question, with a logical next step rather than a page to turn to.
- Warnings and cautions
- Safety content appears before the step it governs and cannot be scrolled past unseen.
- Search and navigation
- Full-text and structured search, a content tree, and a way back from wherever a link leads.
- The target viewer
- Name the viewer the content must run in, and test the behavior there, not just the schema.
- Updates as data
- Changes ship as revised data the viewer picks up, so a revision does not mean a reissued manual.
A list like this can be tested at acceptance. “Level 4” on its own cannot.
FAQ
Questions We Hear
What is IETM Level 4?
Level 4 corresponds to Class 4 in the U.S. DoD classification of electronic technical manuals: a hierarchically structured IETM, where the content is authored into and maintained in a non-redundant database of data elements and links, then packaged into a run-time version for interactive display. The defining feature is the data underneath, not the screen: a Class 3 manual can look almost the same to the user while still being one linear document.
Where do the IETM classes come from?
From a paper by Eric L. Jorgensen of the Carderock Division, Naval Surface Warfare Center. Its April 1994 version was approved by the Tri-Service Working Group for IETMs for DoD-wide use, with the proviso that it be used for definition only and not as a specification for procurement. It defines Class 0, which it says is not an electronic technical manual, and Classes 1 through 5.
Are IETM levels and IETM classes the same thing?
They name the same five-step idea. Class is the U.S. term from the 1994 paper. Level is how the requirement is usually written in Indian defense procurement, where it is commonly attributed to Joint Services Guide JSG 0852. Published descriptions of the levels do not all draw the boundaries the same way, so ask what a contract means by its number before pricing it.
Is there an IETM Level 5?
On paper, yes. Class 5 is Class 4 content integrated in one database with other processes, such as expert-system rules, diagnostics, or training. The 1994 paper itself said Class 5 could only be loosely defined, and it required the integration to happen in the database, not just in a shared user interface.
Is a PDF manual an IETM?
No. An indexed PDF of a page-based manual fits Class 1, electronically indexed page images, which is an electronic technical manual but not an interactive one. The 1994 paper says the IETM specifications do not apply to these page-oriented systems. The first class it calls an IETM is Class 3.
What should a contract specify instead of an IETM level?
The standard the content is prepared to, such as MIL-STD-40051E or S1000D under its business rules, the viewer it must run in, and the behaviors it must show: applicability filtering, working links, fault isolation dialogs, warning display, search, and updates delivered as data. A level number alone leaves all of those open to interpretation.
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