The IBM internal specification language used in the 1980s, particularly at the IBM Hursley Laboratory, is commonly referred to as IBM's Specification Language (SL). Developed internally during this period, it was designed to support formal software specification, incorporating elements of set theory, logic, and type safety. A key feature was its associated "specification checker" tool, which e...

You’re almost certainly thinking of VDM — the Vienna Development Method — and, more specifically, the VDM specification notation used inside IBM in that period (often called Meta‑IV at the time, later standardized as VDM‑SL).

Why this matches your recollection

• Origin in IBM: VDM grew out of work at IBM’s Vienna Laboratory in the 1970s (initially “Vienna Definition Language” for formally definin...

You are almost certainly thinking of VDM – the Vienna Development Method – and its specification language VDM-SL.

Why it fits what you remember

1. Origin inside IBM
   • VDM grew out of work done in the IBM Vienna Laboratory in the early-to-mid-1970s.
   • The group (Peter Lucas, Hans Bekič, Dines Bjørner, Cliff Jones, …) was originally chartered to give a formal semantics of PL/I. The met...

Back in the early‐to‐mid 80’s almost every big systems group at IBM experimented with “formal” or at least “semi‐formal” specification notations, and the one you ran into was not Z, Larch or RAISE but IBM’s own internal flavour of the Vienna Development Method (VDM-SL). In IBM-speak it was usually just called “the Specification Language” (or more formally “VDM–SL”), and it shipped with a PL/I-wri...

IBM's Internal Specification Language of the 1980s

Based on your description, you're likely referring to Vienna Development Method (VDM), which was one of IBM's most significant formal specification languages developed in the 1970s and used throughout the 1980s.

About VDM

VDM was developed at IBM's Vienna Laboratory (hence the name) and became one of the earliest formal methods for spe...

First, I sh...

This is an excellent question that delves into a fascinating period of software engineering history at IBM. Based on your description, the specification language you are recalling is almost certainly the notation used in the Cleanroom Software Engineering methodology, specifically the Box Structure Method.

Here is a breakdown of why this is the likely answer and what happened to it.

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Based on the description provided, the IBM internal specification language from the 1980s was most likely PL/I-FORMAC or possibly CLEAR (Computer Language for the Expression of Abstractions and Requirements).

However, given the specific details mentioned - particularly that it was:

• Used internally at IBM in the 1980s
• Independent of programming languages like PL/S
• Embodied set theory...

The language you were shown inside IBM was the Vienna Development Method notation – internally it was usually called “META-IV”, and outside IBM it later became known as the VDM Specification Language or simply VDM-SL.

What it was
• A model-based formal specification language created in the IBM Vienna Laboratory in the early 1970s.
• Its vocabulary is typed set theory: sets, sequences, maps,...