One question that came from my previous post, Understanding the ISO 15926 RDL, was “What is an endpoint?” The comparison I had made to a dictionary was understood, but “Is there more?” Well, yes:
Q. What is an Endpoint?
A. An endpoint is just a place to store stuff, with the provision that ISO 15926 tools can query it and get a response.
But that probably doesn’t help you very much so I will address this in two parts. The first part, here, develops the dictionary metaphor a bit more; in the second part we will get into some of the different kinds of “stuff” you can store at an endpoint
For the purposes of a gentle introduction here, you can think of an endpoint as the electronic equivalent of a physical dictionary sitting on a shelf at a particular location. A physical dictionary will be a particular edition published by a particular organization. The location it is sitting at is unique in the world. When we (people) refer to such a dictionary in conversation we usually don’t repeat the organization, edition, and the precise location in space because other humans will understand the implied information. (And if they don’t, will ask questions.) But when we create ISO 15926 endpoints that machines can use we need to take all of this implicit information and say it clearly.
If you are new to information modeling, some of the process will seem silly to you. “Everyone knows this!” is a common retort. The problem is that “Everyone doesn’t always know.” And as we move farther and farther from our home area, the proportion of our information that “Everyone doesn’t always know” only grows.
Endpoint Example – The Public Works Dictionary of Evanston, Illinois
We will use the Department of Public Works in the City of Evanston, Illinois in an example of using an endpoint for definitions in order to remove ambiguity in the city’s contracts.
Note to readers: This is a purely fictional example. All we know for sure is that Evanston has a gorgeous beach and at least one wonderful neighborhood of stately old homes similar to the Garden District in New Orleans. (And, no, we have not been paid to say this.)
Evanston, Illinois is a city in the United States just north of Chicago. In case you are interested, its geographic coordinates are 42°2′47″N, 87°41′41″W, with an elevation of 600 ft. It was founded sometime around 1830 by French explorers who called the area “Grosse Pointe” after a point of land jutting into Lake Michigan. Today it is a modern city pretty much contiguous with Chicago–if you miss the sign “You are now entering Evanston” you will never know you’re there.
For our example, let us say that Evanston has suffered a number of lawsuits in its public works projects due to different interpretations of what it thought were common words. To make its public works contracts more transparent it examines the problematic wording. It turns out that there are two classes of common misunderstanding. First, American English is very similar to, but slightly different than, British English, which has made problems for international bidders. Second, a couple dozen of the words used in local commerce date back to the afore-mentioned French explorers and while they have become embedded in local culture and are well-understood within the city, have different meanings to outsiders.
After a search for the most efficient means of standardizing its contract language the city adopts two dictionaries. First, the American English Dictionary published by the Cambridge University Press in Cambridge, England from which most of the words in its contracts will be drawn. Second, the Evanston Public Works Dictionary consisting of the two dozen or so words with a local meaning. All bidders for Evanston public works contracts are invited to look first in the Evanston Public Works Dictionary and second, in the American English Dictionary.
In the pre-internet world the City of Evanston would make paper copies of the two dictionaries freely available in a publically-accessible location. A good choice would be their public library. It might advertise the location as follows.
Copies of the Evanston Public Works Dictionary and the American English Dictionary are available to the public in the Evanston Public Library, 1703 Orrington Ave., Evanston, Illinois, USA, which has geographic coordinates of 42°2′47″N, 87°41′41″W, and elevation of 600 ft. above mean sea level. (They want to eliminate ambiguity and responses such as “Oh, you meant that Evanston over there! I thought you meant this Evanston over here!)
In the internet age, the city might publish the website of the home page for American English Dictionary at http://dictionary.cambridge.org/dictionary/american-english/.
In addition it would add an “Evanston Public Works Dictionary” page to the cityofevanston.org website.
ISO 15926-style Endpoint
To make these definitions operate more like the way ISO 15926 handles definitions, the city might work with the Cambridge University Press to make all of the words in its dictionary individually accessible. For this, each word would be given its own web page. (In the ISO 15926 world we call these individual web pages a URI–look it up.) Similarly, each of the two dozen or so words in Evanston’s Public Works Dictionary would also be given its own web page.
Furthermore, each bidder would be instructed to use some special software that would link each word in its bid to that word’s web page, in essence validating that the bidder was agreeing to the official definition of each word.
In the next post we will discuss some of the things that can be stored at an endpoint.