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Information About HealthXML XML (Extensible Markup Language) is a W3C Recommendation for creating special-purpose markup languages. It is a simplified subset of SGML, capable of describing many different kinds of data. Its primary purpose is to facilitate the sharing of structured text and information across the Internet. Languages based on XML (for example, RDF, SMIL, MathML, XSIL and SVG) are themselves described in a formal way, allowing programs to modify and validate documents in these languages without prior knowledge of their form. Table of contents 1 Strengths and Weaknesses 2 Syntax rules in XML 3 Document Type Definitions and XML Schemas 4 Displaying XML on the web 5 XML Extensions 6 Processing XML files 7 Versions of XML 8 See also 9 External links Strengths and Weaknesses The features of XML that make it particularly appropriate for data transfer are : compatibility with web and internet protocols simultaneously human- and machine-readable format support for Unicode representing all current and many historical character sets the ability to represent the most general computer science data structures (records, lists and treess) the format is self-documenting in that it describes the structure and field names as well as specific values strict syntax makes the necessary parsing algorithms fast and efficient. XML is also heavily used for document storage and processing, both online and offline: robust, logically-verifiable format based on international standards hierarchical structure suitable for most (but not all) types of document plaintext files, unencumbered by licenses or restrictions platform-independent, so relatively immune to changes in technology has already been in use (as SGML) for long over a decade, so there is extensive experience and software available. The weaknesses of the format relates to matters of efficiency, since the XML is not compressed still requires further parsing to extract individual values. modelling overlapping (non-hierarchical) data structures requires extra effort. For matters of generic, loosely bound data transfer the strengths outweigh weaknesses, and in many neutral applications where efficiency is not a particular concern XML is also coming to be adopted simply because tools to manipulate XML are now conveniently on-hand. Syntax rules in XML An XML document is text, usually Unicode although other encodings may be used. Unlike, for example, HTML, XML is highly dependent upon structure, content and integrity for its efficacy. In order for a document to be considered "well-formed" [1], it must conform (at the very least) to the following: It must have one (and only one) root element. Non-empty elements must be delimited by a start-tag and an end-tag. Empty elements may be marked with an empty-element tag. All attribute values must be quoted. Tags may be nested but may not overlap, that is each non-root element must be completely contained in another element. Element names in XML are case-sensitive: for example and are a well-formed matching pair whereas and are not. Also, again unlike HTML, clever choice of XML element names allows the meaning of the data to be retained as part of the markup. This makes it more easily interpreted by software programs. As a concrete example, a simple recipe expressed in an XML representation might be: Flour Yeast Warm Water Salt Mix all ingredients together, and knead thoroughly. Cover with a cloth, and leave for one hour in warm room. Knead again, place in a tin, and then bake in the oven. Identifying information accurately enables programs to manipulate it easily: in this example, it is now easy to convert the quantities to other measuring systems, or to print the ingredients as icons for those with low reading skills (or different native language), or to refer to the individual ingredients or steps from elsewhere (another recipe, for example). An XML document that meets certain other criteria in addition to being well-formed (such as complying with an associated DTD) is said to be "valid". Document Type Definitions and XML Schemas Before the advent of generalised data description languages such as SGML and XML, software designers had to define special file formats or small languages to share data between programs. This required writing detailed specifications and special-purpose parsers and writers. For a language based on XML, however, the software designer can specify the basic syntax by writing a DTD, or a more detailed description using an XML Schema. There are readily available (and in some cases free) tools which understand these descriptions -- XML parsers and writers. This may significantly reduce life-cycle development cost. Displaying XML on the web As a further adjunct to XML is the stylesheet language XSL, which allows users to describe visual properties and transformations of XML data without embedding those instructions into the data itself. The resulting document is then an HTML document which uses CSS for rendering. An XML document may also be rendered directly in some browsers such as e.g. Internet Explorer 5 or Mozilla with the stylesheet language CSS. This process is still not yet stable as of January 2003. The XML document must include a reference to a style sheet: While browser-based XML rendering develops, the alternative is conversion into HTML or PDF or other formats on the server. Programs like Cocoon process an XML file against a stylesheet (and can perform other processing as well) and send the output back to the user's browser without the user needing to be aware of what has been going on in the background. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License. Our site features the latest RSS and XML feeds about Health from leading medical and health related websites. We provide links to these articles about cancer as a public service and hope that you will find them useful. However, we are not responsible for the content of these cancer articles or and we do not endorse or recommend any of the cancer-related websites or pages/images we link to. Use of our site constitutes acceptance of our disclaimer. A Collection of News Feeds About Health
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