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@ -11,34 +11,36 @@ Isn't hypermedia just a way to link documents together? Like with HTML, on the
What do you mean hypermedia _systems_? What do you mean hypermedia _systems_?
Well, yes, HTML is _a_ hypermedia format. But there is more to the way The Web works than just that: HTTP, the Hyper Text Well, yes, HTML is _a_ hypermedia format. But there is more to the way The Web works than just that: HTTP, the Hyper Text
Transfer Protocol is what transfers HTML from servers to clients, and there are a lot of details and features associated with it: Transfer Protocol, is what transfers HTML from servers to clients, and there are a lot of details and features associated with it:
caching, various headers, response codes, and so forth. And then, of course, there is the _hypermedia server_, which caching, various headers, response codes, and so forth. And then, of course, there is the _hypermedia server_, which
presents a _hypermedia API_ to clients. presents a _hypermedia API_ to clients.
And then there is the all-important _hypermedia client_, the software client that understands how to render a _hypermedia And then there is the all-important _hypermedia client_, a software client that understands how to render a _hypermedia
response_ intelligibly to a human, so that a human can interact with the remote system. The most widely known and used response_ intelligibly to a human, so that a human can interact with the remote system. The most widely known and used
hypermedia clients are, of course, web browsers. Web browsers are perhaps the most sophisticated pieces of software we hypermedia clients are, of course, web browsers. Web browsers are perhaps the most sophisticated pieces of software we
use, not only understanding HTML, CSS and many other file formats, but also providing an entire JavaScript runtime use. They not only understand HTML, CSS and many other file formats, but they also provide a JavaScript runtime
built in to themselves that is so powerful, people can create whole applications with it. that is so powerful that web developers can create applications nearly as sophisticated as _thick clients_, that is,
native applications.
So powerful, indeed, that, today, developers often toss aside the _hypermedia_ features of the browser, in favor of This JavaScript runtime is so powerful, in fact, that today many developers set aside the _hypermedia_ features of the
building their web application entirely in JavaScript. An application built in this manner has come to be called browser in favor of building their web applications entirely in JavaScript. Applications built in this manner have come
a Single Page Application (SPA): rather than navigating between pages, the application uses JavaScript that to be called a Single Page Applications (SPAs). Rather than navigating between pages using hyperlinks and forms, these
communicates with a server using JSON API calls over AJAX, and updating the user interface dynamically, completely applications use JavaScript for updating the user interface. When they communicate with a server, these applications
outside the "normal" hypermedia flow of The Web. typically use JSON API calls over AJAX, often updating the user interface using "reactive" style front-end JavaScript
libraries.
HTML, in these applications, becomes a (somewhat awkward) graphical interface description language that must be used HTML, in these applications, becomes a (somewhat awkward) graphical interface description language that is used
because, for historical reasons, that's what happens there, in the browser. because for historical reasons that's what happens there, in the browser.
Applications built in this style are not Hypermedia-Driven Applications, and they do not take advantage of the hypermedia Applications built in this style are not _hypermedia driven_: they do not take advantage of the hypermedia
system that The Web was designed to be. system that The Web was designed to be.
So, to explain what a Hypermedia-Driven application is, and to contrast it with the popular SPA approach of today, So, to explain what a hypermedia driven application looks like, and to contrast it with the popular SPA approach of today,
we need to talk about the entire _hypermedia system_ of The Web and not just HTML. We need to look at the network we need to first talk about the entire _hypermedia system_ of The Web, not just HTML. We need to look at the network
architecture, how a server delivers a hypermedia API, effective use of hypermedia features available in the architecture, including how a server delivers a hypermedia API, as well as effective use
hypermedia _client_ (e.g. the browser). of hypermedia features available in the hypermedia _client_ (e.g. the browser).
These are all important aspects of building an effective piece of software that uses hypermedia, and it is the entire Each of these are important aspects of building an effective hypermedia driven application, and it is the entire
_hypermedia system_ that comes together to make hypermedia such a powerful approach to building distributed software. _hypermedia system_ that comes together to make hypermedia such a powerful approach to building distributed software.
== What is a Hypermedia System? == What is a Hypermedia System?
@ -51,25 +53,26 @@ distributed software.
We define a _hypermedia system_ as a system that adheres to the REST-ful network architecture in Fielding's original sense of We define a _hypermedia system_ as a system that adheres to the REST-ful network architecture in Fielding's original sense of
this term. Unfortunately, today, you probably associate the term REST with non-hypermedia JSON APIs, since that is where this term. Unfortunately, today, you probably associate the term REST with non-hypermedia JSON APIs, since that is where
the term is typically used. A cursory reading of Fielding's dissertation will show that a system _must_ use a _hypermedia_ the term is typically used in industry. A cursory reading of Fielding's dissertation will show that a system _must_ use
like HTML to be REST-ful, a topic that Fielding has commented on repeatedly (and exasperatedly.) a _hypermedia_ like HTML to be REST-ful, a topic that Fielding has commented on repeatedly (and exasperatedly.)
In his dissertation, Fielding was describing The World Wide Web, as it existed in the late 1990s, as being REST-ful. The In his dissertation, Fielding was describing The World Wide Web, as it existed in the late 1990s, as being REST-ful. The
Web, at that point, was simply web browsers exchanging hypermedia. *That* system, with its simple links and form, was what Web, at that point, was simply web browsers exchanging hypermedia. *That* system, with its simple links and form, was what
Fielding was calling REST-ful. JSON APIs were a decade away from becoming common in web development. Fielding was calling REST-ful. JSON APIs were a decade away from becoming common in web development.
So, while JSON API developers may have co-opted the term REST (a long story, for later in this book), the fact of the So, while JSON API developers may have co-opted the term REST (it's a long story, we will tell it later in this book),
matter is that, if you have ever built a simple website using nothing but HTML and a web server, you have built a more the fact of the matter is that, if you have ever built a simple website using nothing but HTML, some links and a basic
REST-ful system, a more REST-ful API, than the vast majority of those JSON API Developers. web server, you have built a more REST-ful system, a more REST-ful API, than the vast majority of those JSON API Developers.
== Hypermedia-Driven Applications == Hypermedia-Driven Applications
In this book we are going to take a look at hypermedia as a _system architecture_, and then explore some practical, In this book we are going to take a look at hypermedia as a _system architecture_, and then explore some practical,
_modern_ approaches to building applications using it. We will call applications built using this architecture _modern_ approaches to building applications using it. We will call applications built using this architecture
_Hypermedia-Driven Applications_, or HDAs, and contrast them with a popular model in use today, the Single Page Application. _Hypermedia-Driven Applications_, or HDAs, and contrast them with a popular model in use today, the Single Page Application,
or SPAs.
A Hypermedia-Driven Application is simply an application built on top of a _hypermedia system_ and that respects A Hypermedia-Driven Application is simply an application built on top of a _hypermedia system_ and that respects
and utilizes the hypermedia functionality of that system. and utilizes the hypermedia functionality of that underlying system.
== Goals == Goals
@ -114,7 +117,8 @@ a refresher.
Hypermedia isn't seriously discussed very often these days. Even many older programmers who grew up with The Web Hypermedia isn't seriously discussed very often these days. Even many older programmers who grew up with The Web
in the late 1990s and early 2000s haven't thought much about these ideas in over a decade. Many younger web developers have in the late 1990s and early 2000s haven't thought much about these ideas in over a decade. Many younger web developers have
grown up knowing nothing but SPAs, and, in particular, building React-talking-to-Node-via-JSON-APIs, and have never grown up knowing nothing but Single Page Applications and the frameworks associated with this approach. In particular,
many young web developers began building React.js applications that interact with a Node server using JSON, and have never
learned about hypermedia at all. learned about hypermedia at all.
This is a tragedy, and, frankly, a failure on the part of the thought leaders in the web development community to properly This is a tragedy, and, frankly, a failure on the part of the thought leaders in the web development community to properly
@ -124,10 +128,9 @@ By the end of this book, you will have the tools and the _language_ to put this
applications. And, further, you will be able to bring the ideas and concepts of hypermedia systems applications. And, further, you will be able to bring the ideas and concepts of hypermedia systems
to the broader web development community. to the broader web development community.
Hypermedia can compete, hypermedia _can win_, hypermedia _has won_ as an architectural choice against the SPA/JSON Hypermedia can compete, hypermedia _can win_, hypermedia _has won_ as an architectural choice against the Single
juggernaut, but _only_ if smart people (like you :) learn about it, build with it and then tell the world about it. Page Application juggernaut, but _only_ if smart people (like you) learn about it, build with it and then tell the world
about it.
Let's go.
[quote, Kyle Reese, Terminator 2: Judgement Day] [quote, Kyle Reese, Terminator 2: Judgement Day]
____ ____