Components and/or widgets (in my view) already play and will play a major role in making up semantic web.
Components can be viewed as building blocks of future web ‘pages’ and are most likely (and already are to a great extend) reusable on any web page – with applications like iGoogle users are able to ‘build’ their own web pages by adding widgets to the page through various interactions including dragging and dropping.
Each component can encapsulate all its attributes (including meaning, structure, data, presentation and behaviour) and can exist on its own by being explicitly linked to various server resources such as pictures and style sheets.
Semantic component structure
Here is an overview of how I am looking at things at the moment and how things may (and already do to a great extent) work within semantic web environment.
Meaning
Outlines what the component means and is placed on the top of the stack because meaning is the most important aspect of semantic web.
Future pages are most likely to be ‘built’ out of components which may reside in any place on the web (i.e. ubiqutous web), hence if the two components on a single page have the same meaning confusion is most likely to arise.
Communicating the meaning of the data we are working with is today’s ultimate goal of good interface developers and generally software engineers.
Structure
HTML is the main (at least the most widely adopted and supported) language with which we can define the structure of a given web page.
There are obviously various ‘flavours’ of HTML we can opt for, but whichever version of HTML we choose to work with, it ought to validate against W3C specifications.
Furthermore, HTML strucuture can (and should) include (wherever possible) microformats.
They are machine readable aspects of semantic web and have already become part of the standards to a great extent and will be adopted more and more over time.
XHTML2 recommendation proposes the use of <section> tag to denote all sections on page.
This nicely leads into future structure of the web within which we could have standalone sections for various mash-up style web sites being developed by developers and integrated into the end system by users.
Data
Data layer is a slightly weird aspect of semantic web as it often contains meaning within it, but due to the fact that most data is not ‘formally’ structured that meaning is mostly lost, hence we need to use layers above to denote structure and meaning of data.
RSS is a good example of (fairly well) structured data which can carry within itself plenty of meaning (RSS used for news for example can be a very structured and semantic way of sharing data).
However, due to the fairly flexible structure of RSS specification, various developers have bastardised it and used it for sharing ‘everything’ through RSS, which, to a great extent, misses the semantic aspects of sharing data through XML feeds.
Plenty of data within web pages these days is also fairly loosely structured. Think about an average paragraph content within a <p> tag in an HTML page.
Presentation
CSS is the main technology we use these days in order to style pages.
They are a very simple technology, which offers massive scope for being misused to a great extent, and that misuse is to a large extent associated with many developers not understanding the nature of semantic web.
Good stylesheet structure and reusability is incredibly important for creating good quality and nice looking semantic interfaces today.
Behaviour
JavaScript is the final part of the current semantic technology layer cake.
It is interesting in its nature in so far that it can ‘dig’ into any of the so far described layers and is therefore subject to all those rules and some more, in order to make it work with less capable browsers.
In order to make the most of JavaScript and enhance the meaning of semantic components which are developed, JavaScript ought to be used in such a way as to add dynamic, behaviour based meaning to those components which help users better understand the purpose of the component and make its functionality more useful.
All of the above put together may make compound semantic web pieces of ‘data’ (semantic objects) which can be used and reused within any context and viewed through any type of browser.
Written by Jason Grant, BSc, MSc on 27th June 2008
Tags: Architecture, css, HTML, javascript, xml