1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta name="author" content="Basho Technologies" />
<meta name="description" content="Webmachine's approach to resource functions and referential transparency" />
<meta name="keywords" content="webmachine http rest web" />
<meta http-equiv="content-type" content="text/html;charset=utf-8" />
<link rel="stylesheet" href="css/style-1c.css" type="text/css" />
<title>Webmachine's approach to resource functions and referential transparency</title>
</head>
<body>
<div id="content">
<h1><span class="hr"></span><a href="/">webmachine</a></h1>
<ul id="top">
<li><a href="/">Home</a></li>
<li><a href="http://bitbucket.org/justin/webmachine/">Source Code</a></li>
<li><a href="contact.html">Contact</a></li>
</ul>
<div id="left">
<h3>Webmachine's approach to resource functions and referential transparency</h3>
<p>
Webmachine goes to great lengths to help your <a href="resources.html">resource functions</a> to be as referentially transparent as possible. By "referentially transparent" we mean that given the same input <code> {ReqData, Context} </code> the function will return the same output <code> {Result, ReqData, Context} </code> and that side effects will be insignificant from the point of view of Webmachine's execution.
</p>
<p>
We don't try to force you into pure referential transparency; we give you as big a hole as you want via <code>Context</code>. As that term is application-specific, you can put database handles, server process identifiers, or anything else you like in there and we won't try to stop you.
</p>
<p>
However, all Webmachine really cares about is the rest of the terms. Since resource functions are generally referentially transparent at least with regard to those terms, many things are easier -- testing, <a href="debugging.html">debugging</a>, and even static analysis and reasoning about your Web application.
</p>
<p>
Note that there is one important exception to this. The <a href="streambody.html">streamed body feature</a> exists to allow resources to consume or produce request/response bodies a hunk at a time without ever having the whole thing in memory. While the continuation-passing style used in the streaming API is friendly to general functional analysis, due to the necessary side-effect of reading or writing to sockets the stream bodies cannot be treated in quite the same way as other uses of the <code>ReqData</code> interface. Luckily, it is easy to inspect a <code>ReqData</code> to see if this is the case in any individual resource or request instance.
</p>
</div>
<div id="footer">
</div>
</div>
<script type="text/javascript">
var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
</script>
<script type="text/javascript">
try {
var pageTracker = _gat._getTracker("UA-4979965-5");
pageTracker._trackPageview();
} catch(err) {}</script>
</body>
</html>
|
