9/11/2023 0 Comments Simple diagrams sdxml![]() ![]() It is also a leaf node and has only a comment c: Comment nodeĪ comment node is similar to a processing Processing instructions that start with `xml' + whitespace The instruction is a sequence of zero or more characters, withoutĪny restrictions, except that the sequence may not start with the threeĬharacters `xml' (upper, lower or mixed case) followed by a space or PIs at all, apart maybe from the and ones.]Ī processing instruction (PI) node is always a [Actually, I am leaning towards the idea that we don't need If the first expression in the document is not `', theĭocument has an anonymous root. Such a document node is represented in the documentīy the absence of a `' expression. The root node of the XML tree may be an anonymous document node, without a There is one exception to the rule that a document node must have a type. ![]() Lexical constraints as the type of an element and the URL has no The type and URL are again character strings. One child that is an element node must be its last child. In other words, if this document node is not the root, its Processing instruction nodes data nodes are not possible.Īlso, if this document node is not the root node of the document, then The other children, if any, must be either comment nodes or A document node looks likeĮlement node and furthermore it must have type p, the same as theĭocument type. The intent of the URL is to specify a specializedĭata model for this node and its children. Document nodeĪ document node is a specialized kind of element Names may not start with the four letters "xml-" (upper or lower case), as The attribute name "id" (upper or lower case) is reserved for somethingĬalled the ID of the element. Values, in particular they may be empty (but see under ` Escape mechanism' below). There are restrictions on the lexical structure of the type andĪttribute names: they must consist of (Unicode) letters, (Unicode) digits,ĭashes and dots, they must be at least one character long and they must The type, attribute names and attribute values consist of strings ofĬharacters. Note that if m=0, the two expressions above are equivalent,Īnd indeed one can use either one at will. Thus, the same node can be linearized with different expressions.įurthermore, all the a i are different, but the In contrast to the children, the order of the attributes doesn't matter. Ordered list of children c i, and a set ofĪttributes, which are pairs of attribute names a i and attribute values A i. ![]() The tree that an XML document represents has a number ofĪn element node is created by expressions like the Generalization of a similar mechanism in HTML.) The linking model is (minus the `#'), so the third q points to the first. `id.' In this case the first q has an id with the same value as the href The last q has an `href' attribute and it points to an element with an The tree corresponding to this document can be visualized ForĮxample, in the following document there is a root node with three children,īut one of the children has a link to one of the other children: Most of the lexical structure is devoted to defining that tree, but there isĪlso a way to make connections between arbitrary nodes in a tree. The main structure of an XML document is tree-like, and XPath 2.0 Data Mode, describes another data model for A more recent document, The XQuery 1.0 and Note also that this document discusses one Linearization, others are part of the information content.įor a different, and much more formal approach, see `ADT and marshalling for XML.' Some of the characters in the document are only there to support the Almost everything will follow naturally from that. Structure and the character strings together form the information content AtĮvery node in the tree there are several character strings. Think of an XML document as a linearization of a tree structure. All those more restrictedĪpplications will share some common invariants, however, and it is those The data model for XML is very simple - or very abstract,ĭepending on one's point of view. ![]()
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