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XML schema definition languages are founded on recommendations laid down by the World Wide Web Consortium (W3C). They use XML 1.0 syntax and aim to explicit describe the structure of XML documents and constrain the data which they may contain. They offer a distinct improvement on the more limited schema features offered by the Document Type Definition (DTD) recommendation which formed part of the original XML specification released in 1998. The most widely used schema language is the one defined by the W3C in 2001: W3C XML Schema. However, there are alternatives, such as RELAX NG and Schematron.

Schema documents are the more sophisticated successors to DTDs and overcome some key limitations associated with them. Firstly, DTDs do not support data types. Secondly, DTDs do not support namespaces. Thirdly, DTDs do not allow developers to accurately define the number of permitted occurrences of elements within their parent element.

An XML schema is concerned with the structure of an XML instance document by defining what each element must or may contain. An element is limited by its type. For example, an element of complex type can contain child elements and attributes, whereas a simple-type element can only contain text. The diagram below gives a first look at the types of XML Schema elements.

Three main purposes are fulfilled by schema documents. Firstly, they can be used to validate XML documents. Secondly, they can be used as a dictionary or grammar for the creation of a given class of XML document. And, thirdly, they can be used to provide documentation for XML documents.

An XML schema is itself an XML document and it contains definitions of all elements and attributes permitted in a class of XML documents. The schema also specifies the structure or hierarchy to which elements must adhere and the type of content each particular element may contain. Elements may be of the simple or complex type. Complex type elements may contain child elements as well as attributes. Simple type element may only contain data. XML documents using a particular schema are referred to as instances of the schema. An XML instance that correctly adheres to its associated schema is said to be valid.

Validation is normally the key role of schema documents. Validation offers many benefits. It ensures the consistency of data within a document. It ensures that data has the right structure and internal hierarchy. It ensures that data within the document structure is of the correct type. It allows us to receive data from multiple sources.

Most XML documents are produced by programs and scripts written to extract information held in databases and transform it into XML. However, it is also possible for human beings to create XML documents. Schemas can be used during this process to assist in the document creation process. XML schemas also provide a mechanism for documenting XML documents and form an important part of the specification of XML vocabularies.

Author is a developer and trainer with Macresource Computer Training, an independent computer training company offering XML Classes in London and throughout the UK.

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I’m sure you have heard that blogging takes time to take off. Yet I have seen many bloggers who make the mistakes of giving up early when the matter of fact is, they are on the right track. So how do you tell?

1. Growing subscriber count – I’ll admit I made this mistake with my first blog. I expect subscribers to grow huge within 2 months. When I said large, I’m talking about at least 10k subscribers. That’s not realistic. It does happen to bloggers, don’t get me wrong, but it’s rare. As long as you have a growing subscriber count, you’re making progress.

2. Increasing numbers of inbound links – Links determine your search engine rankings. It makes it easy for people to find your site. There’s only two ways you can increase your links. It’s either you write long useful articles or you do guest blogging. Personally, I recommend both.

3. Increasing numbers of valuable comments – Comments are always great to have. It shows to your visitors that there are actually people who read your blog. We all have this herd mentality embedded in us. If many find it interesting, usually we would have no problem to agree to it. That’s how visitors work as well.

4. Increasing visitors and pageviews – Many bloggers are stats junkies. While growth in traffic isn’t always representative of meeting or surpassing your blogging goals, it certainly isn’t a bad thing. There are many channels for you to market your blog and increase your visitors. Guest posting and making use of social media is some of the ways to reach out to new readers. If you make use of these channels, over time your blog stats will increase as more and more readers visit and subscribe to your blog.

5. Consistent posting – This is big. Consistent posting is the key to blogging success, and I don’t think there is any exception. If you are posting consistently, you’re already one step ahead of the vast majority of bloggers.

6. Improving quality of articles – Though this may be a subjective issue, but I think most bloggers can make good comparison through going through their older posts. If the quality of your articles improves overtime, which it should, you’re on the right track.

7. An increasing network of bloggers – Networking is crucial. Look at it this way; bloggers support each other. Instead of seeing other bloggers as your competitors, try to see them instead as your partner. By networking with other bloggers, you are more likely to get links, guest blogging opportunities and comments.

Nik Imran is the author of IMakeABlog, a blog that provides guide on how to make a blog. If you are interested in building your own blog, check out his guide on how to install wordpress. Get a totally unique version of this article from our article submission service

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