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What is an XML Parser?

written by: Ada Stoy•edited by: Michele McDonough•updated: 6/30/2011

XML is one of the most popular languages for the Web and XML parsers are one of the things that make it work. Learn more about what XML parsers are and what types of XML parsers exist.

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    Why XML Parsers Are Necessary

    XML parsers are small, but essential XML goodies you can't do without. As the name implies, XML parsers are used to parse XML documents and access the data in them. XML parsers are not the only parsers – actually every program that reads input uses a parser of some kind but due to a variety of reasons, such as the popularity of XML, XML parsers became more well-known than the other types of parsers.

    Usually XML parsers come as a part of a larger package and you might not even be aware that there is an XML parser integrated, unless it breaks just when you need it most. In addition to integrated XML parsers, there are also standalone XML parsers you can get and integrate with your applications. XML parsers are different from XML editors, such as Syntext Serna or Oxygen XML Author.

    The function of XML parsers is to dissect the XML document, get access to the data in it, and make this data accessible to other modules in the program. Since browsers are one of the kinds of applications where access to XML data is necessary, most browsers have built-in XML parsers. One of the functions of the built-in XML parsers is to convert XML into a JavaScript accessible object (the XML DOM), which can later be manipulated in many ways.

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    Types of XML Parsers

    As an additional benefit, many XML parsers also check if the XML document is well formed and if it is valid. However, the main purpose of an XML parsers is not to check and validate XML documents because this is what XML validators are for. This is why one of the frequent classifications of XML parsers is into validating and non-validating.

    Validating XML parsers not only check if the document is well-formed but they also check if it conforms to a specific DTD (Document Type Definition). The DTD can be internal or external. Validating XML parsers are especially useful when you use your custom DTD because they will check for you if your XML conforms to the custom DTD.

    Non-validating XML parsers are simpler. They don't check the validity of your XML against a DTD – they just check if the XML is well-formed or not.

    XML parsers are language-specific. Some of the most popular XML parsers are written in Java and their advantage is that they can be deployed on any platform. However, there are XML parsers in almost any programming language, such as PHP, C, perl, Python, etc. Actually, almost any vendor who has anything to do with XML offers an XML parser and very often these XML parsers are free even for commercial use.