02-xml basics (1) - compatibility...

웹 기술 및 응용

XML Basics

Instructor: Prof. Young-guk HaDept. of Computer Science & Engineering

2019년 2학기

2웹기술응용설계

목차

q Introduction to XML

q XML Document Structure and Basic

Syntax

Introduction to XML


XML (eXtensible Markup Language) 개요 (1)

q What “extensible” means in XMLØ “Capable of being extended”Ø Means that you can define your own markups

q Markups (Tags)Ø Information added to content of a text that enhances its

meaning

o Demarcates or labels parts of a text

Ø Types of markups in HTML

o Semantic Markup: describes the meaning of content

• E.g.) <TITLE>, <BODY>

o Stylistic Markup: describes how to present the content

• E.g.) <FONT>, <B>

o Structural Markup: describes the structure of content

• E.g.) <P>


XML (eXtensible Markup Language) 개요 (2)

q Markup language

Ø A set of markups that can be placed in a text for a specific purpose

Ø E.g., HTML, WML, VRML, SensorML, MathML, VoiceXML, …

q XML

Ø Extensible markup language = meta-markup language

Ø A set of rules to build a markup language and to handle the documents

o I.e., family of technologies to describe how to define tags, transform documents, retrieve data, present data, and so on

q XML document

Ø A document having its content demarcated by XML tags

Ø Set of new tag definitions with XML tags


XML의 역사

1970

1986

1991

1998

SGML

HTML

XML

q 1986: SGML (Standard Generalized

Markup Language)

à International Standard

(ISO)

q 1998: XML 1.0

à De Facto Standard (W3C)

q 2004: XML 1.1

q 2006: XML 1.1 (2nd Edition)

q 2008: XML 1.0 (5th Edition)

GML (IBM)

WWW


Example of XML Document (1)

q All XML documents are

made up of markups and

contentsØ Semi-structured

documents

Ø Markups and contents

complement each other

Ø Markups create an

information entity with

partitions

Ø Markups create an

labeled data in a handy

package

<?xml version=“1,0”?>

<letter priority=“important”>

<to>John</to><subject>CS760</subject><message>

Don’t forget to attendthe class<emphasis>on Friday </emphasis>

Good luck to you.</message>

<from>Tomas</from></letter>


Example of XML Document (2)

1 실 세계의 BMW 차

BMW 차에 대한 XML 문서

XML 저작 도구:BMW 차에 대한 XML 문서 작성

3

2

BMW


XML vs. HTML (1)

q HTML은 미리 정의된 tag만을 사용, XML은 tag를 확장가능

q HTML tag들은 주로 content를 화면에 보여주기 위한 방법 제공, XML

tag들은 문서의 구조화 혹은 content에 대한 labeling 방법 제공

q XML은 tag 명칭의 대/소문자를 구분

우편번호라는 사실을 알기 어려움

화양동

화양동


XML vs. HTML (2)

q XML 문서

Ø XML tag를 이용해서 labeling함으로써 content의 의미를 표현 가능

<zip>450-3490</zip>화양동


XML vs. Other Electronic Documents

q HWP 및 MS Word 문서

Ø 비표준화된 전용의 이진 파일 형태로 저장

Ø 문서 구조 정보가 없고 문서 내용과 스타일이 혼합

Ø 외부 프로그램에서 문서 사용 및 처리의 자동화가 어려움

q XML 문서

Ø 일반 text 파일 형태로 저장하여 모든 컴퓨팅 플랫폼에서 판독 가능

Ø 문서를 구조, 내용 및 스타일로 각각 분리하여 관리

o 문서 구조: DTD나 XML Schema를 기반으로 정의 (document model)

o 문서 내용: document model에 맞추어 content 작성 (valid XML document)

o 문서 스타일: 문서 내용을 표현하기 위한 스타일 정의 (XSL, CSS)

Ø 외부 프로그램에서 문서 사용 및 자동화된 처리가 용이함


Benefits of XML Documents

q 다른 전자 문서와 비교한 XML 문서의 장점

Ø 데이터의 독립성

o 문서의 구조(DTD, XML Schema)와 내용(document)을 분리

Ø 다양한 표현

o 동일한 문서 내용을 다양하게 표현이 가능 (CSS, XSL)

Ø 데이터 교환이 용이

o Text 및 개방형 웹 표준 기반

Ø 데이터 검색 기능 강화

o Semi-structured 문서로서 데이터 검색이 용이 (XPath, XQuery)

Ø 문서 구조의 변형(transform)이 용이

o E.g., XML 문서 à HTML 문서 (XSLT)

o E.g., XML 문서 à MS Word, HWP, PDF 등 binary 문서 (XSLT-FO)


XML Technology Family

문서구조

DTDXML SchemaSOX…

문서 링크

XPathXPointerXlink…

파생 언어

WMLXHTMLMathML…

문서 스타일

XSLTXSLT-FOXSL, CSS…

문서 API

SAXDOMJDOM…

서비스

SOAPWSDLUDDI…

저장 및 검색

XML-DBMSNXDXQuery…

보안

EncryptionSignature…

XML

XML Document Structure and Basic Syntax


XML 기본 용어 (1)

q Element

Ø Labeled container of content

Ø Basic building block of XML documents

<to type = “name”>

Hong Gildong

</to>

Element“to” 속성 (Attribute)

시작 태그 (Start tag)

내용 (Content)

마침 태그 (End tag)


XML 기본 용어 (2)

q 적절한 문서 (Well-formed document)

Ø 브라우저나 다른 프로그램에 의해 처리될 수 있도록 해주는 최소한의 규약인

XML 기본 문법을 준수한 문서

1) It contains only properly-encoded legal Unicode characters

2) None of the special syntax characters such as "<" and "&" appear except

when performing their markup-delineation roles

3) The begin, end, and empty-element tags which delimit the elements are

correctly nested, without missing and overlapping

4) The element tags are case-sensitive; the start and end tags must match

exactly

5) There is a single root element which contains all the other elements

q 유효한 문서 (Valid document)

Ø 해당 문서의 문서 모델에 맞는 문서

o DTD (Document Type Definition)

o XML Schema


적절한 (Well-Formed) 문서의 예

q 정확히 하나의 최상위 (root) 엘리먼트를 가져야 함

Ø 적절한 문서: <jumin> … </jumin>

q 태그가 올바르게 둘러싸여져야 함 (correctly nested)

Ø 적절한 문서: <jumin><name>kim</name></jumin>

Ø 적절하지 못한 문서: <jumin><name>kim</jumin></name>

q 각 엘리먼트가 시작 태그와 마침 태그를 모두 가져야 함

Ø 적절하지 못한 문서: <name>kim 또는 kim</name>

q 시작 태그명과 마침 태그명이 같아야 함 (대/소문자 구분 포함)

Ø 적절한 문서: <name>kim</name>

Ø 적절하지 못한 문서: <name>kim</age>, <name>kim</Name>


Well-formed 및 Valid Document 검사


XML 문서 구조

<memo><to what=“name”>홍길동</to><date>2002/04/05</date><contents>전화 요망</contents><from>허준</from>

</memo>

XMLDeclaration

Document TypeDeclaration(생략가능)

Prolog(생략가능)

Elements(Contents)

<?xml version=“1.0” encoding=“euc-kr”?>

<!DOCUMENT memo [ <!ELEMENT memo (to, …)>

…]>


간단한 XML 문서 구조의 예

XML 문서 내용(Elements)

XML 선언


Example of XML Document

XML 선언

XML 문서 내용(Elements)


Root Element

Tree View of the Example Document Structure

Element

Content

Attribute


Structure of XML Documents

q XML Document :=

Prolog? Element

q Prolog

Ø Tips off the world that the

document is marked up in

XML

q Element

Ø Root element (Document

element)

Ø Other elements


Prolog

q Prolog :=

XMLDecl DocTypeDecl?

q Top of XML document is graced

with special information

Ø XML Declaration

o The document is marked up in XML

o Example

<?xml version=“1.0”?>

Ø Document Type Declaration

o Defines name of the root element

o Defines DTD (Document Type

Definition) reference

à document model


XML Declaration

q XMLDecl := “<?xml” versioninfo encodinginfo? standaloneinfo? “?>”

Ø versiono E.g., version=“1.0”

Ø encodingo “euc-kr”: Korean encoding

o “UTF-8”: 8-bit Unicode (default)

Ø standaloneo “yes”: No external file to load

o “no”: Some files to load (default)

• When there is an External Entity

• When DTD is in an external file

q Examples<?xml version=“1.0”?><?xml version=“1.0” encoding=“euc-kr”?>

* Note “<? … ?>” tag comes from SGML


Document Type Declaration

q DocTypeDecl :=

“<!DOCTYPE” root-element extID-of-dtd?(“[” internal-subset “]”)?

“>”

q Document Type Declaration

Ø Defines name of the root element

Ø Defines DTD (internal subset)

o For document validity checking

o Defines ELEMENT and ENTITY declarations

q External subset reference

Ø extID-of-dtd refers to an external

subset for document type declaration

* Note “<! … !>” and “[ … ]” tags come from SGML


Document Type Declaration Example (1)

DTD

Root Element


Document Type Declaration Example (2)

External ID of DTD


Element: Building Block of XML Documents

q Element :=<name (att1=“value1” att2=“value2” …)? >

content</name>

q Empty Element :=

<name (att1=“value1” att2=“value2” …)? />

q Example

<Caution class=“info”>Start, End tag should be pair!Name is case-sensitive!Whitespace in content is preserved!Following element is empty element.<EmptyElement/>

</Caution>


Element: Building Block of XML (cont’d)

q Naming rules

Ø Starts with a letter or underscore (_)

Ø Should not start with “xml”, “Xml”,“xMl”, “xmL”, …, or “XML”

Ø Contains letters, numbers, hyphen (-),

period (.) and underscore (_)

q Positioning rules for well-formed documents

Ø End tag must come after the start tag

Ø Elements should be correctly nested

o There should be no overlapping elements

o An element’s start and end tags must both

reside in the same parent


Element: Building Block of XML (cont’d)

q Element definition examples

Ø <Err>Case-sensitive</err> à </Err>just do it</Err>

Ø <1st>Don’t Start with Number</1st>à <first> … </first>

Ø <Xml_tag>Don’t Start with “xml”<Xml_tag>

Ø <err></err> à <err></err>

Ø <e rr></err> à <err></err>

Ø <emptyElement/>

o Is equal to <emptyElement></emptyElement>

o Is not equal to <emptyElement> </emptyElement>because whitespaces are preserved in XML content


Attribute: More Muscle for Elements

q Attribute :=

name = “value” | ‘value’

Ø Gives elements unique properties

Ø There can be many attributes in an element (unordered)

Ø Attributes are separated by whitespaces (not comma)

Ø Attribute names should be unique within an element

Ø If the attribute value itself contains double (or single) quotes we can use

single (or double) quotes around them

q Examples

Ø <letter priority=“high” type=“1”/>== <letter type=“1” priority=“high”/>

Ø <choice test=‘msg=“hi”’> or <choice test=“msg=‘hi’”>

Ø <team person=“sue” person=“joe”>à <team person1=“sue” person2=“joe”>


Attribute: More Muscle for Elements (cont’d)

q Attribute Value Types (in DTD)Ø ID

o Validating XML parser warns you if the ID doesn’t have a unique value through out the document (attribute “no” in the example below)

Ø IDREF(S)o Validating XML parser warns you if the IDREF points to a nonexistent

element (attribute “with” in the example below)

Ø Other types: ENUMERATED, CDATA, ENTITY(S), NMTOKEN(S)

q Example<part no=“bolt-100”/><part no=“bolt-100”/><part no=“bolt-123”/><part no=“nut-123”>

<compatible with=“bolt-123”/><compatible with=“bolt-456”/>

</part>


Entity: Placeholder for Content

q Entity

Ø Contains a part of XML document

Ø Something like macro in C (#define): “Declare once, use many times”Ø Doesn’t add anything semantically to the markup

Ø Always eliminate an inconvenience

o From standing in impossible-to-type characters

o To marking the place where a file should be imported (external entity)

q Example in the internal-subset

<!DOCTYPE letter ...[

<!ENTITY w3url “http://www.w3.org/”>]><letter>

<message>Hi. John. W3 URL is &w3url;</message></letter>

<message>

Hi. John. W3 URL is

http://www.w3.org/

</message>


Entity: Placeholder for Content (cont’d)

Used inDTD



q Character Entity

Ø Predefinedo Ampersand(&): ampo Apostrophe(‘): apos

o Greater than(>): gto Less than(<): lto Quotation(“): quot

Ø Numbered (Unicode from #0 to #65536)

o E.g., cedilla(ç): #231

o Alphabetic, syllabic, ideographic scripts

• Latin

• Greek

• 20,000 Han ideographs

• 11,000 Hangul ideographs, ...

Ø Named (user defined)o E.g., <!ENTITY cedilla “ç”>

<!ENTITY name “Kim”>



q Mixed-Content Entity

Ø Contains content of unlimited length

Ø Can include markup as well as text

o Internal entity

E.g., <!ENTITY phone “<number>042-999-9999</number>”>

o External entity

E.g., <!ENTITY signature SYSTEM “./signature.xml”>



q Example

à External entity



External entity

imported from“./signature.xml”



q External Entity Example

<!ENTITY part1 SYSTEM “./p1.xml”>

<!ENTITY part2 SYSTEM “http://www.bobsbolts.com/p2.xml”>

<!ENTITY part3 SYSTEM “http://www.tomsnuts.com/p3.xml”>

à Local file

à www.bobsbolts.com

à www.tomsnuts.com



q Unparsed Entity

Ø Should not be parsed by XML parser

o Tells parser not to load the entity’s content

o Normally used for applications

Ø May contain something other than text

o E.g.) Binary image files

<!ENTITY mypic SYSTEM “./erik.gif” NDATA GIF>

à “GIF” is name of notation data (NDATA) declared as

<!NOTATION GIF SYSTEM “image/gif”>



q Parameter Entity

Ø Only occur in the document type declaration section

o Preceded by ‘%’ (not by ‘&’)

Ø Parameter entity references are immediately expanded in

the document type declaration

o E.g., without parameter entity

<!ELEMENT burns (#PCDATA | quote)*>

<!ELEMENT allen (#PCDATA | quote)*>

o E.g., with parameter entity

<!ENTITY % pcont "#PCDATA | quote">

<!ELEMENT burns (%pcont;)*>

<!ELEMENT allen (%pcont;)*>



q External Parameter Entity

Ø External parameter entity

<?xml version="1.0" standalone="no"?>

<!DOCTYPE class [

<!ENTITY % professor SYSTEM "http://www.univ.com/professor.dtd">

<!ENTITY % rec_room SYSTEM "http://www.univ.com/lec_room.dtd">

<!ENTITY % student SYSTEM "http://www.univ.com/student.dtd">

%professor;

%lec_room;

%student;

]>

Miscellaneous Markups

q Comment :=

“”

Ø Tells parser to ignore those regions

Ø Within comments, “--” should not occur

Ø E.g., 

q Processing Instruction :=

“<?”keyword data? “?>”

Ø Container for data targeted toward specific applications or parsers

Ø E.g., <?linebreak?><?xml version=“1.0”?>


q CDATA Section :=

“<![CDATA[” any_text_and_markup “]]>”

Ø Tells parser the section contains no markup

o Should be treated as a regular text

Ø Within a CDATA section, “]]>” should not occur

Ø E.g.) Using “<“ and “>” in CDATA section

Miscellaneous Markups (cont’d)

with CDATA Section

]]>


References

q XML 1.0 (Fifth Edition)

Ø W3C Recommendation 26 Nov. 2008

Ø http://www.w3.org/TR/xml

http://www.w3.org/TR/xml