I've specialized in formal language design and implementation since the 80's, often as a consultant, and built some successful systems. In 1986, I consulted to a former client in silicon valley that had changed names from CADTec to Sherpa. They were building what would later be called 'configuration management' systems. These always needed human interfaces, and so I designed and built a few with them. One language was just called PDQ, or 'product data query', essentially a query translator in front of the database. PDQ became the heart of a system called Sherpa DMS (Data Management System), a customizable design-and-construction workflow application that became heavily used by the aerospace industry throughout the 90's. It helped with logistics and engineering management, a field then called 'Product Data Management' which would later be called 'Product Information Management' and later 'Lifecycle Management'. Most jetliners produced in the 90's were designed using Sherpa DMS. It was still in use after the dotcom boom, and might still be embedded in some legacy systems today. PDQ might have been the first object-oriented query language in a successful commercial product. It's hard to tell, since such subsystems are often hidden, and most products are lost. Also, it's hard to call PDQ an object-oriented query language, in our contemporary sense (I'm writing in 2017) since the intention was not to integrate with o-o languages, whose compilers were still not yet considered reliable commercial products in 1986, but instead to offer an optional approach to describing relations among products, parts, and attributes -- an approach simpler than relational query languages of mid-80's database products, but which would be implemented on top of them. Utimately, this set of features propagated into almost all general-purpose query languages. The ideas had been floating around in labs for years, so I'm not sure if this implementation was a primary influence -- but it was certainly successful enough to be influential. A few years later, several of my colleagues at Sherpa formed a successful rival company known as Agile Software. Here are my working papers for the initial implementation, finished in the summer of 1986. It's a nice example of the process required to delineate any query language's denotational semantics.
