XSDs assure that your XMLs have the type of input that you expect. You don't care what kind of input you get, you just want input. Advantages (disadvantages) of Schemas: Advantages (disadvantages) of DTDs: Allow you to limit the values of an element: Have a simpler syntax: Support namespaces, so that you can include different XML vocabularies within a document: Require fewer lines of code to create: Are represented using XML syntax It is because of the lack of types with the text files that the original problem occured. There are several different languages available for specifying an XML schema. These constraints are generally expressed using some combination of grammatical rules governing the order of elements, Boolean predicates that the content must satisfy, data types governing the content of elements and attributes, and more specialized rules such as uniqueness and referential integrity constraints. How can I make it so that all the letters on a word are all capitalized yet the first letter is bigger than the rest? XSD's are not the only XML schema available. [11], This article is about XML schemas in general. Keeping a repository of XMLs without an XSD is akin (in my opinion) to having a database where all the types are declared as VARCHAR(n). There are historic and current XML schema languages: The main ones (see also the ISO 19757's endorsed languages) are described below. Asking for help, clarification, or responding to other answers. In theory, the lack of a specific list allows a processor to support data types that are very problem-domain specific. But XML was everywhere in the enterprise world at the time. The association may be achieved via markup within the XML document itself, or via some external means. Also, by using schemas, you can enable validation in your XML parser, making it easier to tell when some piece of code fails because it's given some bad XML. Which, in theory, means that using a RELAX NG schema across multiple validators requires either providing those user-defined data types to that validator or using only the two basic types. This is a list of notable XML schemas in use on the Internet sorted by purpose. the root element,