How ISO 15926 Works
Getting machines to communicate with each other is similar to getting two people to communicate with each other.
Imagine two people, each with their own native language, together learning a new foreign language. They will first learn the names of objects they are familiar with, essentially building a new dictionary. Then they will learn to master a new way of expressing ideas, which is learning new rules of grammar. When they have mastered the dictionary and the grammar, they can communicate with each other freely.
The same is true of machines. When two machines use the same definitions and structure their data the same way, they can communicate freely too. Admittedly, this is not a trivial statement (or we would have been doing this years ago) but is the key to understanding how ISO 15926 works.
- Part 2 is the data model, equivalent to the rules of grammar
- Part 4 is the reference library, equivalent to the dictionary.
When information is structured according to Part 2, and the definitions follow Part 4, machines will be able to communicate freely as well. This is the core of ISO 15926.
Part 2 is quite specialized. Fortunately it is not necessary to master Part 2 in order to use it. Part 7 is a collection of data constructs that you use in combination. For instance, to build a typical equipment data sheet you would use a number of templates over and over, each with different definitions from Part 4, to build a representation of the equipment. Each piece of information would know what it is. When you send this to a business partner, his ISO 15926 interface would also understand what all the individual data items mean, and push the appropriate data values to his own database.
- Part 7, the templates, is equivalent to a phrase book for a foreign language which allows you to construct meaningful sentences without having to learn the entire language.
Of course to actually communicate the machines need some medium by which to exchange information. For instance, while learning their new language the two people in the example above will practice writing it on some media. In a classroom they might use a white board; in other places perhaps a paper notebook. Each of these methods of recording ideas requires the users to follow some protocol. But in every case, the information they are recording is separate from the medium on which it is recorded. This is analogous to Part 8. OWL and RDF are a way of recording information in a standard ontology so that the context is preserved, but the information is still separate from the medium.
Eventually these two students may master the new language well enough that others seek them out. At first the two may play host at a local coffee shop. Later they may be able to rent an auditorium and charge an entrance fee. If their popularity continues to grow they might create a web site with a paywall where readers create an account and pay a fee, perhaps one fee for read-only and a higher fee to be able to download a copy. This is analogous to Part 9. But again, the access is separate from the information.
- Part 8, made up of some Semantic Web tools called Resource Description Framework (RDF) and Web Ontology Language (OWL), is like paper in a book, or a computer file
- Part 9, called the facade, is like the postal service
Thus, Part 2 and Part 4 (and Part 7, which makes it easier to use Part 2) are the core of ISO 15926. Part 8 and Part 9 are methods of accessing the information.
(In An Introduction to ISO 15926 we show in more detail how the parts of the standard work together, and show how two organizations, starting very simply, gradually implement more and more of ISO 15926.)
The idea of separating the data model from the reference library was developed in the heat of battle on a number of large, world class projects over a number of years.