snu oopsla lab. xml documents 1 : structure the ubiquitous xml(2) © copyright 2001 snu oopsla lab

SNUOOPSLA Lab.

XML Documents 1 : Structure

The ubiquitous XML(2)

© copyright 2001 SNU OOPSLA Lab.

2SNUOOPSLA Lab.The ubiquitous XML

XML Documents 1 : structure

Peeping into XML document at Physical view : Entity at logical view : DTD

XML document

Peeping into XML document(1/5)

<?xml version=“1.0” standalone=“yes”?>

<GREETING> Hello, XML!! </GREETING>

Mark-updata

Mark-up and character data

XML document

<? xml version=“1.0” standalone=“yes” ?>

<!DOCUMENT DATE [ <!ELEMENT DATE (#PCDATA)>] >

<DATE> 001224</DATE>

XML document : date.xml

XML declarationxml 문서임을 선언 .<? 로 시작하여 ?> 로 끝난다 .

DTD(Document Type Definition)user 가 사용할 tag 를 정의한다 .여기서는 DATE tag 를 정의 .

Content

 Comment : parser 는 이를 무시 .

XML document


Structure of XML document

physical structure : allows components of the document, called

entities

logical structure : allows a document to be divided into named

units and sub-units, called elements


XML document

Sub-unit

Unit

Document

elements

Logical Structure

entities(internal)(separate)

Physical Structure

SNUOOPSLA Lab.5


XML document


XML document

<person>

<name> kim </name>

<ID>771224</ID>

<office>301-453</office>

<phone>1830</phone>

<photo source=“k.jpg”/>

</person>

<person>

<name> kim </name>

<ID>771224</ID>


<phone>1830</phone>

<photo source= />

</person>

“k.jpg”

element

entity



Content of Physical structure

Entity Figures of Document Entity Defining an entity Grammar in Declaring Entity Examples of EntityDeclaration URL format

Physical structure

Entity (1/3) unit of physically isolating and storing any

part of a document ( 정보저장단위 ) Each unit of information is called an entity

entities(internal)(separate)

Physical Structure

<person><name> kim </name>

<ID>771224</ID>


<phone>1830</phone>

<photo source= />

</person>

“k.jpg”

entity

SNUOOPSLA Lab.

Physical structure


Entity (2/3) Purpose of Entity

contain all the information (well-formed XML data , other text file, binary

data…)

<person><name> kim </name> <ID>771224</ID>

<office>301-453</office><phone>1830</phone>

<photo source= />

</person>“k.jpg”

Document entity

Image entity

Physical structure


Entity (3/3) Internal Entity

해당 document 안에서 완전하게 정의되는 entity

External Entity URL 을 통해 알려진 외부의 source 로부터 그들의

content 를 받아 오는 entity

Physical structure


Figures of Document Entity

document entity(no entities)

document entity(main content)

A

A

B

C

D

document entity(framework file)

Physical structure


Defining an entity Entity must be defined before the first reference to

them in the data stream Declared in the DTD(Document Type Definition)

<!DOCTYPE DOCUMENT [

<!ENTITY EMAIL “[email protected]”> <!ENTITY TEXT “(#PCDATA)”>

]>

Entity definition in DTD

Physical structure


Example : EntityDeclaration(1/3)

Internal text entities <!ENTITY XML “eXtensible Markup Language”> <!ENTITY DemoEntity ‘The rule is 6” long.’>

Built-in entities ( 내장 entity) <!ENTITY sample “Use " and ‘as delimiters.”>

&li; >&'"

for ‘<‘for ‘>’for ‘&’for ‘ ’ ’for ‘ ” ’;

Physical structure



External text entities <!ENTITY myent SYSTEM “/EMTS/MYENT.XML”> <!ENTITY myent PUBLIC “-//MyCorp//ENTITY

Syperscript Chars//EN”….>

Binary entities <!ENTITY Jsphoto SYSTEM “/ENTS/Jsphoto.tif”

NDATA “TIFF”>

Physical structure


<!ENTITY ent9 SYSTEM “entities/entity9.xml”> /xml/document.xml/entities/entity9.xml

<!ENTITY ent9 SYSTEM “../entities/entity9.xml”>

/xml/docs/document.xml/ entities/entity9.xml

xml

document.xmlentities

entity9.xml

xml

entities

entity9.xml

docs

document.xml

URL format

SNUOOPSLA Lab.

Physical structure


Concepts DTD Structure Element Declaration Attribute Declarations Parameter Entities Conditional Sections Notation Declarations DTD Processing Issues

Content of Logical structure

logical structure


DTD(Document Type Definition) An optional but powerful feature of XML Comprises a set of declarations that define a

document structure tree XML processors read the DTD and check whether

the document is valid and use it to build the document model in memory

Describes user’s own tag set as meta markup language

Concepts of DTD(1/3)

logical structure


Concepts of DTD(2/3) DTD describes..

Element , attribute , notation , relation between each elements

Establishes formal document structure rules


Declare Vs. Define Declare “This document is a concert poster” Define “A concert poster must have the

following features” DTD define

Element type + Attribute + Entities Valid Vs. Invalid

Valid conforms to DTD Invalid fail to conform to DTD

Well formed XML Document

Valid XML Document

Concepts of DTD(3/3)

logical structure


Valid & Invalid Documents

Valid:<GREETING>various random text but no markup</GREETING>

Invalid: anything else including<GREETING>

<sometag>various random text</sometag> <someEmptyTag/>

<GREETING>

logical structure

Example: <!DOCTYPE GREETING[<ELEMENT GREETING (#PCDATA)>]>


DTD is composed of a number of declarations ELEMENT (tag definition) ATTLIST (attribute definitions) ENTITY (entity definition) NOTATION(data type notation definition)

DTD can be stored in an external subset or an internal subset

DTD structure

logical structure

Internal subset Form : <!DOCTYPE … [  … ]> Pros

Easy to write XML Cons

Editing two files without moving Other document can’t reuse without copying

internal subset

Internal and External Subset(1/3)

logical structure


External subset better to use external DTDs Reason why?

Many benefits document management updating editing

Few reasons If you use an external DTD, you can use public DTDs(capability) External DTDs provide for better document management External DTDs make it easier to validate you document


logical structure



internal

external

Internal subset

external subset

full parsing path

logical structure


Used to define a new element, specify its allowed content and gives the name and content model of the element

Each tag must be declared in a <!ELEMENT> declaration.

The content model uses a simple regular expression-like grammar to precisely specify what is and isn't allowed in an element

ELEMENT Type declaration ‘<!ELEMENT’ S Name S Contentspec S? ‘>’

Element Declarations

logical structure


Content Specifications ANY #PCDATA Sequences Choices Mixed Content Modifiers Empty

logical structure


A SEASON can contain any child element and/or raw text (parsed character data)

Rarely used in practice, due to the lack of constraint on structure it encourages.

<!ELEMENT SEASON ANY>

ANY

logical structure


Parsed Character Data; i.e. raw text, no markup

Represent normal data and preceded by the hash-symbol, ‘#’, to avoid confusion with an identical element name, when used within a model group( for example, ‘(#PCDATA | PCDATA)’)

<!ELEMENT YEAR (#PCDATA)>

#PCDATA

logical structure


Use of #PCDATA in XML Valid: Invalid:

<YEAR>1999</YEAR><YEAR>99</YEAR><YEAR>1999 .E.</YEAR><YEAR> The year of our Lord one thousand, nine hundred, and ninety-nine</YEAR>

<YEAR><MONTH>January</MONTH><MONTH>February</MONTH><MONTH>March</MONTH><MONTH>April</MONTH><MONTH>May</MONTH><MONTH>June</MONTH><MONTH>July</MONTH><MONTH>August</MONTH><MONTH>September</MONTH><MONTH>October</MONTH><MONTH>November</MONTH><MONTH>December</MONTH></YEAR>

logical structure


Child Elements To declare that a LEAGUE element must

have a LEAGUE_NAME child:

<!ELEMENT LEAGUE (LEAGUE_NAME)> <!ELEMENT LEAGUE_NAME (#PCDATA)>

logical structure


Sequences(1/2) Separate multiple required child

elements with commas; e.g.

One or More Children +

<!ELEMENT SEASON (YEAR, LEAGUE, LEAGUE)><!ELEMENT LEAGUE (LEAGUE_NAME, DIVISION, DIVISION, DIVISION)>

<!ELEMENT DIVISION_NAME (#PCDATA)><!ELEMENT DIVISION (DIVISION_NAME, TEAM+)>

logical structure


Sequences(2/2) Zero or More Children *

Choices

<!ELEMENT TEAM (TEAM_CITY, TEAM_NAME, PLAYER*)><!ELEMENT TEAM_CITY (#PCDATA)><!ELEMENT TEAM_NAME (#PCDATA)>

<!ELEMENT PAYMENT (CASH | CREDIT_CARD)>

<!ELEMENT PAYMENT (CASH | CREDIT_CARD | CHECK)>

logical structure


Grouping With Parentheses

Parentheses combine several elements into a single element.

Parenthesized element can be nested inside other parentheses in place of a single element.

The parenthesized element can be suffixed with a plus sign, a comma, or a question mark.

<!ELEMENT dl (dt, dd)*><!ELEMENT ARTICLE (TITLE, (P | PHOTO |GRAPH | SIDEBAR | PULLQUOTE | SUBHEAD)*, BYLINE?)>

logical structure


Mixed Content Both #PCDATA and child elements in a choice

#PCDATA must come first #PCDATA cannot be used in a sequence

<!ELEMENT TEAM (#PCDATA | TEAM_CITY | TEAM_NAME | PLAYER)*>

Empty elements

<!ELEMENT BR EMPTY>

logical structure


Attribute Declarations

Consider this element:

It is declared like this:

<GREETING LANGUAGE="Spanish"> Hola!</GREETING>

<!ELEMENT GREETING (#PCDATA)><!ATTLIST GREETING LANGUAGE CDATA "English">

<!ATTLIST Element_name Attribute_name Type Default_value>

logical structure


Multiple Attribute Declarations

Consider this element

With two attribute declarations:

With one attribute declaration Indentation is a convetion, not a requirement

<RECT LENGTH="70px" WIDTH="85px"/>

<!ELEMENT RECTANGLE EMPTY><!ATTLIST RECTANGLE LENGTH CDATA "0px"><!ATTLIST RECTANGLE WIDTH CDATA "0px">

<!ATTLIST RECTANGLE LENGTH CDATA "0px" WIDTH CDATA "0px">

logical structure


Attribute Types CDATA ID IDREF IDREFS ENTITY

ENTITIES NOTATION NMTOKEN NMTOKENS Enumerated

logical structure


CDATA Most general attribute type

Value can be any string of text not containing a less-than sign (<) or quotation marks (")

logical structure


ID Value must be an XML name

May include letters, digits, underscores, hyphens, and periods

May not include whitespace May contain colons only if used for

namespaces Value must be unique within ID type attributes

in the document Generally the default value is #REQUIRED

logical structure


IDREF Value matches the ID of an element in

the same document Used for links and the like

IDREFS

A list of ID values in the same documentSeparated by white space

logical structure


ENTITY Value is the name of an unparsed

general entity declared in the DTD

ENTITIES

Value is a list of unparsed general entities declared in the DTDSeparated by white space

logical structure


NOTATION Value is the name of a notation

declared in the DTD

<!NOTATION Tex SYSTEM “..\TEXVIEW.EXE”>

<!ENTITY Logo SYSTEM “LOGO.TEX” NDATA Tex>

TEXVIEW.EXE LOGO.TEX

1

2

3

4

logical structure


NMTOKEN Value is any legal XML name

NMTOKENS

Value is a list of XML namesSeparated by white space

logical structure


Enumerated Not a keyword Refers to a list of possible values from

which one must be chosen Default value is generally provided

explicitly

<!ATTLIST P VISIBLE (TRUE | FALSE) "TRUE">

logical structure


Attribute Default Values A literal string value One of these three keywords

#REQUIRED #IMPLIED #FIXED

logical structure


#REQUIRED No default value is provided in the DTD Document authors must provide attribute

value for each element

<!ELEMENT IMG EMPTY><!ATTLIST IMG ALT CDATA #REQUIRED><!ATTLIST IMG WIDTH CDATA #REQUIRED><!ATTLIST IMG HEIGHT CDATA #REQUIRED>

logical structure


#IMPLIED No default value in the DTD Author may(but does not have to)

provide a value with each element

logical structure


#FIXED Value is the same for all elements Default value must be provided in DTD Document author may not change default

value

<!ELEMENT AUTHOR EMPTY><!ATTLIST AUTHOR NAME CDATA #REQUIRED><!ATTLIST AUTHOR EMAIL CDATA #REQUIRED><!ATTLIST AUTHOR EXTENSION CDATA #IMPLIED><!ATTLIST AUTHOR COMPANY CDATA #FIXED "TIC">

logical structure


Example of Internal DTDs

<?xml version="1.0"?><!DOCTYPE GREETING [ <!ELEMENT GREETING (#PCDATA)>]><GREETING>Hello XML!</GREETING>

logical structure


Internal DTD Subsets

Internal declarations override external declarations

<?xml version="1.0"?><!DOCTYPE GREETING SYSTEM "greeting.dtd" [ <!ELEMENT GREETING (#PCDATA)>]><GREETING>Hello XML!</GREETING>

logical structure