What is Linked Data?

Hi, my name is Yulia and I'm a curriculum engineer at Inrupt.

In this video we'll learn about Linked Data and how it is the key to introducing interoperability back to the World Wide Web. We'll start by reviewing what interoperability means and then define Linked Data.

Interoperability is the spectrum of effort that it takes for existing and new entities to communicate with each other. A lot of effort means a lack of interoperability. Currently, it is difficult to accomplish interoperability within a single organization, let alone across multiple tools, services, or products across the web. This is due to the vast number of data schemas, stores, representations, and variabilities between data infrastructures that exist in current applications. The lack of data interoperability is a side effect of data being strongly coupled with applications, making applications largely siloed as well. 

One of the tools that can help us to break out of this siloed world with a deficiency of interoperability is Linked Data. Linked Data is an exchange format for data without boundaries. It allows separate data infrastructures to become interoperable regardless of the schemas, data stores, and data representations that they were built with. Its goal is to break out of the proprietary data silos and enrich the current web with an additional layer of meaningful information such that it can be understood by both a human and a machine with equal ease and simplicity. 

How does that work in practice? Linked Data has four principles:

1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful information.
4. Include links to other URIs, so that they can discover more things.

The acronym URI is used in each of these principles, so let's expand on it. URI stands for Universal Resource Identifier. It is a superset of URL. While the URL locates resources for us, the URI, as the name suggests, identifies them, or as the first Linked Data Principle says, it can be used to name things.

The second principle is to use HTTP URIs, which we will simplify to URLs in these videos. It provides a way for each resource to be uniquely identified and then located. HTTP retrieves the hypertext from the given URI, which when simplified HTTP URI can be restated as: "use URLs so that people can look up those names".

The third principle says that when someone looks up a URI, or URL, useful information must be provided. For example, let's say there is an item in a furniture store, we'll call it Amy's dresser. We can create a webpage that identifies it and check off the first principle. We'll then place it at http://www.furniture.com/amys-dresser and check off the second principle of Linked Data. When someone goes to this address they will find useful information about this dresser on that page, like the fact that it is a dresser, maybe a picture of it, and its dimensions. This is useful information for a person, who knows what height and width mean in this context just by looking at this page. However, a machine will need help with some of these concepts, given that context is not something that machines easily perceive. 

This is when we need to add the fourth principle, which is to include links to other URLs so that more things can be discovered.

This means that the resource at http://www.furniture.com/amys-dresser should include more information. We can add a link to a definition of the dresser, the picture could be a URL instead of a static image, then each dimension could be defined with a URL too.

Why would we be so meticulous in linking data together? Through following these principles we create self-describing data. Linking self-describing data together through the power of existing technology allows for data to gain rich context that is accessible both for human and machine analysis.

This in turn, leads to wider interoperability, where products and services can exchange data without the overhead required to adapt the data from one application to another, breaking down data silos. 

How does this look in practice? And how exactly does this benefit a user, organization, or a market, are all great questions that we will discuss in later videos. For now, let's recap what we've learned so far.

Linked Data is a way to break out of this siloed world with a deficiency of interoperability. It is an exchange format for data without boundaries. Its goal is to enrich the current web with an additional layer of meaningful information such that it can be understood by both a human and a machine with equal ease and simplicity. 

Linked Data is the key to breaking out of proprietary data silos and introducing wider interoperability.

Linked Data Principles are:

1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful information.
4. Include links to other URIs. so that they can discover more things.

Linking self-describing data together through the power of existing technology allows for data to gain rich context that is accessible both for human and machine analysis.

Follow me to the next video to see Linked Data Principles in action.