IT Tips & Tricks
Part 2 of a 3-part Series
Published 5 January 2015
Updated 1 February 2022
How Do File Links Really Work?
Ed Clark, LinkTek COO
In our first article in this series, on “What is a Link Really?”, I covered what a link really is. And, as promised, we can now talk about the details of these links and how they can affect you.
So let’s have some fun with this and use an analogy to really show what file links are all about and how amazing they are (and how they can get you in trouble).
What is a Parent File? What is a Child File?
First, let’s start with a few basics. Then we’ll get to the part where I tell you what this all has to do with pecan pie.
A file that contains one or more links pointing to another file is called a “parent file”. A file that is being pointed to by a link is called a “child file”.
A “link” is a set of instructions placed inside the guts of one file (a parent file) that tells the computer where to look for another file (the child file) and what to do with that child file. This is what a link, in essence, actually is.
A Cool Analogy
Here comes the analogy that will make this so clear and easy that you will never forget it: Let’s say that you are in your office and you need something picked up, each and every day, from another location and brought to you.
So you send for a company courier named “Bob” who walks into your office. You tell Bob that you need the following done at Noon every single day. Then you hand Bob a piece of paper that says:
Drive to the house named “Castle” at address 1810 Lake Drive, Tampa, Florida USA. Get there by going west on Maple Street and then turn left on Lake Drive. It’s the sixth house on the right.
So Bob, being just a CPU and unable to think like a human, never found the house (child file), came back to the office (parent file) and left an empty space where your pie should have been.
When you arrive, pick up the package labeled “Vital Material”. Bring that package back here, then open it and take out the slice of pecan pie and put it on my desk.
Pie, anyone? Metaphorically speaking, the entire purpose of a link is to collect the package from the castle and make sure the contents arrive on your desk. You want this to work. Every time.
- The office where you and Bob are standing is the parent file.
- The house named “Castle” is the child file.
- The address and the directions to the house are the file path.
- The package with the pecan pie is the target data residing inside the child file.
- The courier Bob is the computer CPU that will execute your instructions.
- The full set of instructions (which is everything on the piece of paper) is the link.
That’s what a link really is. It’s a set of instructions residing in one file that tells the computer where to look for another file and what to do when it finds the other file.
If Bob (the computer CPU) drives to the house (the child file), successfully retrieves the package (the target data), brings it back to your office (the parent file) and places the pecan pie on your desk, then the instructions (link) worked correctly, as did Bob. And all is well.
"File Not Found"
Unfortunately, not all file links work correctly all the time. Sometimes the instructions (link) have something wrong in them, such as wrong directions (file path) to the house (child file), in which case Bob would return to your office (parent file) and present you with either nothing or some sort of bad banana (error message). This is called a “broken link”.
Or, in another scenario, the instructions (link) were completely correct — at the time they were written. But recently a local politician named Jonathan changed the name of the street on which the house (child file) resides to “Jonathan Court”. So Bob, being just a CPU and unable to think like a human, never found the house, came back to the office (parent file) and left an empty space where your pie should have been.
So What Went Wrong?
What went wrong here is that someone altered the address of the child file without updating the address in the link. See, the instructions in the link sent Bob (our hapless CPU) looking for a street (folder) named “Lake Drive”. But thanks to Jonathan the politician, there is no street named “Lake Drive” anymore. Bob, being a CPU (not a human) doesn’t possess the ability to look at landmarks and figure out what to do. So he returned back home (parent file) with nothing except that weird marker you get when a graphic is missing from a file.
This is another way to have a “broken link”. And it happens to thousands or millions of files at a time during a “little” thing called a “data migration” which is the subject of my final article in this series. This is where we get to the heart of how this causes so much trouble for you. So go here now.
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