xml validation（二）

最新推荐文章于 2021-03-20 05:49:13 发布

vagabond1

最新推荐文章于 2021-03-20 05:49:13 发布

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分类专栏： xml 学习文章标签： validation xml character structure xhtml html

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本文介绍 XML 文档类型定义 (DTD) 的基本概念及其验证过程。详细解释了 DTD 的不同形式，包括外部 DTD 和内部 DTD 的结构与使用方法。此外，还探讨了元素定义语法和修饰符等关键概念。

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Section 3. Validating a document

Xml document will be parsed as a DOM document or a SAX stream. (What is DOM and SAX stream? We will tell it later)

The parse will also check the structure of document against DTD or schema if it has been configured to do so. It also will create error handler.

--Error Handler will look for it later.

Section 4. DTD(Document Type Definition)

External DTDs

<!DOCTYPE html PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN”>

--<!DOCTYPE : tell the processor it is DOCTYPE declaration.

--html: indicates that the name of the root element for the document. If the document started anything but <html>, it would immediately be deemed invalid.

--PUBLIC : designate a publicly recognized DTD, potentially saving the processor a trip to the server to retrieve it. (What’s meaning?) Other option is SYSTEM.

-- -//W3C//DTD HTML 4.01 Transitional//EN: The actual public identifier for the Transitional XHTML DTD.

For custom DTDs, developers typically use a SYSTEM identifier, such as:

<!DOCTYPE memories SYSTEM "http://www.nicholaschase.com/memories.dtd">

Structure of an internal DTD

<?xml version="1.0"?> <!DOCTYPE memories [ <!ELEMENT memories (memory+) > <!ELEMENT memory (#PCDATA) > > <memories> <memory>TBD</memory> <memory>TBD</memory> </memories>

Variable element content

With a pipe character (|), meaning the data structure contains an element named location that may contain either a place element or a description element. With a pipe character(|) for choicing.

<!ELEMENT location (place | description) >

Modifiers (*, +, and ?)

--*: means an element can appear 0 or more times

--+: means an element can appear 1 or more times.

--?: means an element can appear 0 or 1 time.

For example:

<!DOCTYPE memories[

<!ELEMENT memories (memory*)> --memories can have 0 or more memory

<!ELEMENT memory (media,

subdate,

donor?, --0 or 1 donor

subject+, --1 or more subject