Eric van der Vlist. Publisher: O'Reilly. First Edition June ISBN: -1, pages. The W3C's XML Schema offers a powerful set. If you need a reliable tool for technical documentation, this clear and concise reference will help you take advantage of DocBook, the popular XML schema. by . If you need to create or use formal descriptions of XML vocabularies, the W3C's XML Schema offers a powerful set of tools for defining acceptable document.
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The Infoset defines the data types that are an XML document. – Infoset types largely structural. – Infoset type system non-extensible. • XML Schemas are used to. F.3 XML Schema Validator. F.4 Sab-pyth. F.5 Redfoot. F.6 XML Components for Zope. F.7 Online Resources. Colophon. Dedication. We would like to dedicate. For more information on XML, check out Erik T. Ray's Learning XML (O'Reilly, ) and . And here's an XML Schema that defines the same document type.
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R interface to GCC source code information. Type library information reader. R package version 3. Simon Urbanek. Low-level R to Java interface. Eric van der Vlist. XML Schema. Priscilla Walmsley. Definitive XML Schema. Generate PMML for various models.
Personalised recommendations. Cite chapter How to cite? The names in the start and end tags must be identical. An end tag has to come after never before the start tag. And both tags have to reside within the same parent element.
Violating the last rule is an error called overlapping. These untangled elements are okay: No problemhere Container elements may contain elements or character data or both.
Content with both characters and elements is called mixed content. For example, here is an element with mixed content: I like to ride my motorcycle really fast. Attributes In the element start tag you can add more information about the element in the form of attributes.
An attribute is a name-value pair.
You can use it to add a unique label to an element, place it in a category, add a Boolean flag, or otherwise associate some short string of data. In Chapter 1, I used an attribute in the telegram element to set a priority level. One reason to use attributes is if you want to distinguish between elements of the same name.
For example: When making crop circles, push down gently on the stalks to avoid breaking them. Farmers don't like finding people in their fields at night, so be very quiet when making crop circles. Elements 59 The class attribute might be used by a stylesheet to specify a special typeface or color.
It might format the with a thick border and an icon containing an exclamation point, while the gets an icon of a light bulb and a thin border. The emphasis elements are distinguished in whether they have an attribute at all. The second does, and its purpose is to override the default style, whatever that may be.
Another way an attribute can distinguish an element is with a unique identifier, a string of characters that is unique to one particular element in the document. No other element may have the same identifier. This gives you a way to select that one element for special treatment, for cross referencing, excerpting, and so on. For example, suppose you have a catalog with hundreds of product descriptions. Each description is inside a product element. You want to create an index of products, with one line per product.
How do you refer to a particular product among hundreds? The answer is to give each a uniquely identifying label There is no limit to how many attributes an element can have, as long as no two attributes have the same name. An attribute can have an enumerated value, meaning that the value must be one of a predefined set.
It may be an identifier reference type, requiring that another element somewhere has an identifier attribute that matches. A validating parser will check all of these attribute types and report deviations from the DTD.
Namespaces Some attribute names are reserved in XML. Namespaces are a mechanism by which element and attribute names can be assigned to groups. They are most often used when combining different vocabularies in the same document, as I did in Chapter 1. The part-catalog element contains two namespaces which are declared by the attributes xmlns:nw and xmlns. The elements inside partcatalog and their attributes belong to one or the other namespace. Those in the first namespace can be identified by the prefix nw:.
Example Document with two namespaces torque-balancing hexnut The attributes of part-catalog are called namespace declarations. The general form of a namespace declaration is illustrated in Figure It starts with the keyword xmlns: 1 is followed by a namespace prefix 2 , an equals sign 3 , and a namespace identifier 5 in quotes 4.
Figure Elements 61 Avoid using xml as a namespace prefix, as it is used in reserved attributes like xml:space. In a special form of the declaration, the colon and namespace prefix are left out, creating an implicit unnamed namespace.
The second namespace declared in the example above is an implicit namespace. This is not a requirement, however. The site may not even exist. So why use a URL? The namespace has to be assigned some kind of unique identifier. URLs are unique. They often contain information about the company or organization. So it makes a good candidate. Still, many have made the point that URLs are not really meant to be used as identifiers.
Resources are moved around often, and URLs change.
But since no one has found a better method yet, it looks like namespace assignments to URLs is here to stay.