It is also used to perform validation. There are two types of DTD. They are internal or external. According to the above, the elements are declared within the XML file. So, it is an internal DTD. Each ID, Name and Email are defined separately. They all are parse-able data types. DTD exist from line number 2 to 7.
The rest is XML. When the DTD file is saved as student. It is done as follows;. It is used to define the structure and the content of XML files.
It is a method of expressing constraint of the XML file. There are two types of XSD files. They are simple Type and complex Type. The simpleType allows having text-based elements. It contains fewer attributes, child elements and cannot be left empty.
Pascal Thivent Pascal Thivent k gold badges silver badges bronze badges. On "But what if we wanted size to be an element? XML schema provides secure data communication i. Flow N Randhawa N Randhawa 7, 2 2 gold badges 40 40 silver badges 46 46 bronze badges.
You should explain where "datatype" actually matters for your example. SkyWalker DTD is more limited than XSD as far as occurences with only the choices of 1 , 0 or 1 , 0 or more , while XSD can specify the minimum and maximum number. One difference is that in a DTD the content model of an element is completely determined by its name, independently of where it appears in the document: Assuming you want to have a person element with a child element called name an name itself has child elements first and last.
JaakkoK JaakkoK 7, 2 2 gold badges 31 31 silver badges 48 48 bronze badges. Using the same name name for two different things types is never a good idea. Similarities : DTDs and Schemas both perform the same basic functions: First, they both declare a laundry list of elements and attributes.
Second, both describe how those elements are grouped, nested or used within the XML. In other words, they declare the rules by which you are allowing someone to create an XML file within your workflow, and Third, both DTDs and schemas provide methods for restricting, or forcing, the type or format of an element. Differences: DTDs are better for text-intensive applications, while schemas have several advantages for data-intensive workflows. StackzOfZtuff 1, 21 21 silver badges 20 20 bronze badges.
Doro Doro 1 1 gold badge 16 16 silver badges 31 31 bronze badges. I like your emphasis on "structure"; it's like with syntax diagrams for programming languages : Not every syntactically correct program is semantically correct, and you cannot provide a syntax diagram to allow only semantically correct programs it seems that is what people expect from XSD.
Mike Mackintosh Nirav Daraniya Nirav Daraniya 41 1 1 bronze badge. See my comment on stackoverflow. Robert Robert 41 1 1 bronze badge. Maybe because it's so easy to create XML e. More limited than XSD? Functionality subset of XSD functionality?
Syntax too complex? Hardly, just different IMHO. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. With all of these namespaces floating about, it is easy to confuse them, or to create a namespace collision : a situation where there are conflicting references to a namespace. Practically speaking, that means that redefining elements using Schema can be complicated.
When would you want to redefine an element? With DTDs, redefining or overriding declarations can be pretty easy. If those internal DTD declarations are in conflict with the declarations in the external DTD, then the internal declarations are used. Of course, XML Schema have methods to import or include other XML Schema; however, doing so is not necessarily trivial, and in fact can be quite complex because of namespace issues that might arise from having two elements with the same name, and keeping track of the various namespaces elements belong to.
So if you are using a base schema, but have the need to easily override or extend that schema, a DTD might be a better choice than XML Schema. Everyone talks about the power of XML Schema, especially the power of datatypes. And it is true that datatypes offer a high degree of flexibility and power that was not possible before with DTDs. But not everyone needs that kind of flexibility and power. What if your needs center around large-scale documents which are mostly if not entirely text?
Some examples might include manuals, documentation, encyclopedias, and dictionaries. While these might have some elements used for indexing and cross-referencing, the majority of the elements might simply contain large blocks of text. That's a perfect example of the type of document which might not benefit from an XML Schema. Unless there is a compelling Schema feature which is essential to your document needs, chances are a DTD will satisfy your schema requirements adequately, and quite possibly more efficiently.
You spend six months researching, designing, and writing the perfect XML Schema. It is a thing of beauty, designed to anticipate your every data need. It is compatible with your database Schema and it describes your XML document perfectly. It allows you to do things you could have never done with a DTD, and even though you don't need that functionality now, your foresight will pay off tenfold in the future. You are proud of your work. XML Schema are a fairly new technology.
If the tools you rely upon everyday in order to be productive don't support XML Schema, then you might just have to stick to DTDs for a while. That doesn't mean you can't think about XML Schema, or learn how you might use them in the future. But in the meantime, if your software doesn't support XML Schema, it won't do you much good to use them.
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