Posts Tagged ‘HTML’

Emerging semantic web structure

Friday, June 27th, 2008

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.

Semantic Data Component Structure

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.

Tags: , , , ,
Posted in Advanced, Architecture, Development, Intermediate, Visionary | 1 Comment »

Semantic uses of <div> HTML tag

Friday, June 6th, 2008

What is it for?

W3C specification is fairly clear about what the purpose of <div> tag is.

The full quote from W3C HTML specification is:

The DIV and SPAN elements, in conjunction with the id and class attributes, offer a generic mechanism for adding structure to documents. These elements define content to be inline (SPAN) or block-level (DIV) but impose no other presentational idioms on the content. Thus, authors may use these elements in conjunction with style sheets, the lang attribute, etc., to tailor HTML to their own needs and tastes.

Some on-line references say that <div> tag is ‘semantically neutral‘, but I would strongly disagree with this statement. <div> is essentially there to be used for denoting sections of HTML documents.

<div> tag stands for ‘division’ on page, hence it has a semantic meaning to it which can be infered simply from its name.

Appropriate use

<div>, coupled with and id or a class attributes, is semantically very strong statement which gives a meaningful top level structure to any HTML document.

Structure and top level semantics of HTML pages are very important parts of creating web sites of any size these days.

This aspect of web pages not only helps organise the application for end users, but also helps developers organise the application from the developer perspective, aiding overall usability of software (it is commonly forgotten that usability does not only apply to application interfaces, but also to the back end, as well as general day-to-day life).

We need to think about usability all the time, as we are developing products which need to be maintained and upgraded (scaled) in future in the most meaningful (i.e. semantic) way all-round and not just from the interface point of view.

Web developers who know what they are doing, understand that <div> tag is a very powerful tool in web development and create ‘objects’ on screen which are completely encapsulated within their own <div> tags with a relevant id which uniquely identifies that ‘object’ within any page.

Inappropriate use

How ‘granular’ should we go with <div> tag and what is the smallest amount of code we could surround with a <div>?

I tend to implement standards as strictly as possible, since I have found (over years) that approach to be the wisest approach (least error prone and most scalable).

‘Sections’ or ‘components’ on a page should contain at least 3 tags in order to be considered candidates for being surrounded by <div> tag. (I am sure someone will be able to come up with examples of where this does not stand).

It is important to avoid divitis in order to keep interfaces lean, fast performing and avoid code bloat (and therefore decrease maintainability of the application).

There are many examples within which a <span> will work as well as <div>, but semantically will not be as ‘strong’ as <div> and the code will still work, validate and make more sense.

There are also frequent circumstances within which other elements can be treated as a <div> and therefore use of <div> avoided, while achieving the same results.

Great examples of this situation are usually presented wherever ordered or unordered lists are used, in which cases <li> can (in most circumstances) act as a <div>.

A look into future

An HTML construct such as

<div id="news" class="component">Component content goes here<div>

means a lot and creates a very good structure on a modern web page.

Future automated semantic tools could potentially understand these conventions and be able to ‘pick up’ complete components from pages and create mash-ups which can work with content directly pulled in from any web site.

Treating user interface as an API and standardising HTML mark-up (in a similar way in which Microformats community does it) can enable any portion of any interface to become reusable anywhere.

Name spacing CSS files according to the structure of the <div> component based mark-up also leads to better CSS development, leading towards faster performing and much more scalable and easily re-skinable interfaces and generally smaller and leaner implementations.

Example

Good example of using <div> tag and utilising its full semantic power.

Tags: ,
Posted in Advanced, Development, Intermediate | 3 Comments »

Pareto analysis of HTML

Wednesday, June 4th, 2008

HTML stands for Hyper Text Markup Language. It is a language and it is intended mainly for text. Its initial purpose was to provide meaning to text documents which reside on the World Wide Web.

This initial intention of HTML got somewhat lost in the last 10 years of web development and large majority of web developers are only now waking up to this fact.

I would like to provide Pareto Analysis of HTML as it is used on semantic web development projects on day-to-day basis. Without fully understanding these tags, you are most likely not to be able to create a proper, semantic web site today.

There are around 100 HTML elements which have been made part of the W3C specification. However, only a portion of those tend to be used by developers on day-to-day basis.

Highlighted in the list are those elements which I deem to contain some amount of semantic ambiguity. In other words, developers tends to misunderstand the meaning behind these tags, which tends to lead to their lesser or greater misuse.

I will explain separately the reasons why I think these tags are misused and how they ought to be used.

  1. <div>
  2. <span>
  3. <p>
  4. <a>
  5. <table>
  6. <tr>
  7. <thead>
  8. <tbody>
  9. <td>
  10. <th>
  11. <caption>
  12. <img>
  13. <form>
  14. <input>
  15. <label>
  16. <fieldset>
  17. <textarea>
  18. <select>
  19. <style>
  20. <option>
  21. <legend>
  22. <html>
  23. <head>
  24. <title>
  25. <link>
  26. <meta>
  27. <script>
  28. <body>
  29. <em>
  30. <strong>
  31. <abbr>
  32. <address>
  33. <h1>
  34. <h2>
  35. <h3>
  36. <ul>
  37. <ol>
  38. <li>
  39. <dl>
  40. <dd>
  41. <dt>
  42. <object>
  43. <embed>

With the above list of HTML elements you should be able to semantically mark up pretty much 90% of any small or large web site today.

It is interesting to observe that less than half of the overall HTML specification is used on most web sites today.

This fact suggests that almost half of HTML tag set is obsolete as well as that HTML specification is arguably sufficient for the purposes it was developed for.

Some web developers may disagree with this statement, feeling that HTML is missing elements which could be introduced into HTML5/XHTML2 to make some common tasks easier and faster to complete.

However, in conversations with developers, I have rarely met one who was able to suggest any new tag, letalone one that was meaningful and did not only cover requirements of an average blog site.

Tags: ,
Posted in Advanced, Development | 7 Comments »