Tuesday, August 18, 2009

Web 2.0 interactivity

When a field selector is used to load values or a web interface wants to interact with a back end process, a useful design pattern to use is Ajax MVC.

This works very well with jQuery, PHP and a database.



The model is a map of how data is stored. The model may also provide object structures that inform the view how to use data.


The view is a form with active fields that talk to the controller. The fastest way to make an interactive view is using a smart template system such as TAL or Smarty.


The controller mediates messages from the view, and formats data according to the Model which gets delivered to the view.

Intelligent View

Ajax requires that the View contains scripting that allows page elements to POST and GET data. HTTP has several methods of packaging data to be sent to the server.

RESTful Web services

RESTful webservices conceptually implement PUT and POST. GET is simply used to sent record filters (i.e. selection criteria) and is considered "Safe" - that means that it must never be possible to change data in the Model using a GET. This prevents user database poisoning by URL.

HTML 5 allows PUT - which simply means record establishment. If you PUT a record that already exists - it will create another record, or better, results in an error condition. XHTML does not incorporate PUT, so it is common practise to overload POST.

POST is common to all versions of HTTP and is implemented in HTML 4.x and XHTML. POST packages and sends data via a mechanism (called Standard Input) that is not available for hacking except by modifying the form sending the data. Of course it is possible to do that, so some serialisation or encoding is important, minimally a timestamp and a hash that ensures that the data is recognised as valid.

The Web is distracting

The internet is distracting humanity from the humdrum pointless paper pushing inanity that used to rule us. Now we can share without authority, now we can make things and see them without institutions dictating, but it helps academia prepare our minds.

Compare TED.com with Sarah Palin. One shares ecology and values, educating humanity. The other exposes the mind of a greedy person.

Now, back to Facebook...