ansaurus

Question

Building a JSON Structure to Store Rules for Web Requests

Answer 1

+1 A:

There are a number of ways to build a rudimentary decision engine. If there aren't too many rules involved, you could even model a common decision table structure (conditions & actions) directly in JSON format. As VolkerK mentioned, it is not clear whether client and/or server validation is required.

A really simple format could use bitmasks (popular in Windows API programming :) You can even pass it between client and server side as a simple string. At some point though, the number of rules can become unwieldy. One of our systems at the shop actually uses a business rules engine because of the sheer number of choices.

Here's a little snippet that should output a binary string: 1010001

<!DOCTYPE html>
<html><head><title>Bitmask</title></head>
<body>

<div id="output"></div>
<script type="text/javascript">
var out = document.getElementById('output');

var R_IS_LOGGED_IN    = 1;
var R_HAS_ACCT_TYPE_X = 2;
var R_HAS_ACCT_TYPE_Y = 4;
var R_HAS_USER_NAME   = 8;
var R_HAS_ROLE_X      = 16;
var R_HAS_ROLE_Y      = 32;
var R_VAR_X_IS_A      = 64;
var R_VAR_X_IS_B      = 128;

var attrs_as_string = 
  (R_IS_LOGGED_IN | R_HAS_ROLE_X | R_VAR_X_IS_A).toString(2);

out.innerText = attrs_as_string;
</script>
</body>
</html>

You could then precompute the desired combinations of conditions and possibly use a simple switch/case dispatch table approach:

switch(computed_bitmask) {
  case '11001' : do_this(); break;
  case '1101'  : do_that(); break;
  default: do_whatever();
}

jtp 2010-09-08 07:02:17

Thanks jtpresta, I always wanted to know how bitmask permissions worked - this was helpful!

Kirk 2010-09-09 23:34:32

You are welcome. They can be helpful sometimes :)

jtp 2010-09-15 01:48:19

Answer 2

+1 A:

Check out Amazon S3 Bucket Policies fits the bill. It's already in JSON. Try extending the Conditions with your own and extend the Effect actions to include a message.

http://docs.amazonwebservices.com/AmazonS3/latest/dev/index.html?AccessPolicyLanguage.html

I'd say try looking for an open source Amazon bucket policy creator tool that you can extend but I'm not finding anything with a simple google search.

Rob Olmos 2010-09-08 18:13:02

This was extremely useful, and essentially what I was looking for. Thanks Rob!

Kirk 2010-09-09 23:34:01

ansaurus

tags:

views:

answers:

Building a JSON Structure to Store Rules for Web Requests

related questions