1
eXtensible M
arkup Language
Reda Bendraou Reda.Bendraou@
lip6.fr
http://pagesperso-systeme.lip6.fr/R
eda.Bendraou
XML
2
Agenda
Part I : The X
ML S
tandard
Goals
W
hy XM
L ?
XM
L document S
tructure
Well-form
ed XM
L document
Part II : XM
L: DTD
and Schem
a
DTD
XML Schem
a
3
What is XM
L?
XM
L stands for EXtensible M
arkup Language
X
ML is a m
arkup language much like H
TML
XM
L tags are not predefined. You m
ust define/invent your ow
n tags
XM
L was designed to describe data
XM
L is a W3C
Recom
mendation
4
The Main Difference Betw
een XML and HTM
L
XML w
as designed to store, carry, and exchange data. XM
L was not designed to display data.
XM
L is not a replacement for HTM
L. X
ML and H
TML w
ere designed with different goals:
X
ML w
as designed to describe data and to focus on what
data is.
HTM
L was designed to display data and to focus on how
data looks.
HTML is about displaying inform
ation, while XM
L is about describing inform
ation.
5
How can XM
L be Used?
To describe and to structure data
To Separate Data from
HTML
You need to parse your XM
L document to display data
To parse: CSS, XSLT, DO
M API, etc.
To Exchange Data
To Store Data
6
XM
L Goals
A
need for representing data:
E
asily readable :
That fits to the W
EB technology (to be easily integrated within W
EB servers)
W
ith a clear separation between :
In a standardized w
ay - By humains
- By machines
- presentation aspects (format,
colors, etc..) - Data (sem
antics)
7
XM
L: Origines
Som
e well know
n Formats :
HTM
L = Hyper Text Markup Language (only presentation)
SG
ML = Standard G
eneralized Markup Language (to structure the
document
Tag based Language O
ther notations :
ASN.1= Abstract S
yntax Notation (ITU
-T)
CD
R, X
DR
= Com
mon/eX
tenal Data R
epresentation etc…
..
8
HTM
L Draw
backs
Sim
ple, readable !
WEB Com
patibility! BUT
Not extensible ! (a fixed set of standardized tags and attributes)
M
ixing between the Form
and the Content ! (i.e. presentation tag with a data : <H
1> Intensive Care </H
1>)
Brow
sers / Versions Incompatibility
No way to check the docum
ent: - structure (Tags ordre ), - data (type, value), - sem
antic
9
SG
ML D
rawbacks
pow
erful, extensible, standard (ISO
8879-1986)!
M
eta-language for documenting huge and com
plex
specifications (i.e. automobile, avionic, etc…
)
…Nevertheless
Too com
plex ! -> Too hard to implem
ent, too hard to use !
Not necessarily W
EB com
patible!
10
A D
efinition:
XM
L :
A
n extensible and configurable language
A hierarchical representation of data
http://w
ww
.w3.org/X
ML/
XM
L
- An HTML variant!
(WEB com
patibility, readable, HTML-like syntax)
- A subset of SGM
L !
(flexibility, rigor)
11
XM
L document structure
header :
Equivalent to H
TML <H
EA
D>,
M
eta–data:
body :
Equivalent to H
TML <B
OD
Y>
Structured data :
- Processing instructions - com
ments
(no interpretable by the parser)
- Enclosing tags - Attributes (e.g. <gangster nam
e='Ocean')>
- Data within tags (e.g. <title> O
cean's 12 </title>) (a tree structure)
12
<letter> <location> S
omew
here in space</ location >
<sender> ObiW
an Kenobi </ sender >
<receiver> Luke Skyw
alker </ receiver > <introduction> D
ear padawan, </introduction>
<body_Letter> …May the force be w
ith you </ body_Letter > <signature/>
</letter>
<?xml version = "1.0" standalone="yes" encoding="IS
O-8859-1"?>
XM
L Exam
ple : A letter
A stand alone document
Processing instruction
A single Tag (empty, no data)
Header
Body
Character set used (Latin)
document XM
L
Start tag
End tag
Data
13
XML Prologue
(Example)
<?xml version="1.0" standalone = "no" encoding="IS
O-8859-1" ?>
<!DOCTYPE
liste_CD
SYSTEM "C
Ds.dtd">
A key word ! (Define the docum
ent Type)
This is a non-standalone XML docum
ent (uses an external docum
ent)
In conformity with an external definition
(specified in "CDs.dtd")
XML 1.0 docum
ent
14
XML docum
ent body (Example)
<CD_list> <CD
> <artist type="individual">Frank S
inatra</artist> <title no_pistes="4">In The W
ee Sm
all Hours</title>
<tracks> <track>In The W
ee Sm
all Hours</track>
<track>Mood Indigo</track>
</tracks> <price m
oney="euro" payment="C
B">12.99</price>
<to_buy/> </CD
> <CD
> ….. </CD
> …
.. </ CD_list >
6
8
1
3 5
3 4
2
7 9
15
XM
L document body
(a tree view of the exam
ple)
liste_CD
piste
titre
pistes
artiste
CD
en_vente
piste
CD
prix
racine du document
Fra
nk S
ina
traIn T
he
We
e S
ma
ll Ho
urs
Mo
od
Ind
igo
In T
he
We
e S
ma
ll Ho
urs
12
,99
CD_list
/CD_list
Document Root
tracks
title
track
track
price
to_buy
16
XM
L document body
(som
e explanations)
A
tree-like structure (see slide 12)
The body's root is unique (1)(2).
Tags are either :
The content betw
een a pair of tags (3) is either :
S
ome tags m
ay have attributes (5)(8),
- by pairs : Start (1) ,and End (2), - unique (4).
- A simple value : a string (6), a real (7), etc.,
- A tree structure of other tags (9). - A m
ix of both (not shown in the example).
17
Element Nam
ing N
ames should be short and sim
ple (e.g. <Cd_Title>)
XML elem
ents must follow
these naming rules:
Nam
es can contain letters, numbers, and other characters
N
ames m
ust not start with a num
ber or punctuation characters
Avoid (':', '-', '.', '!', etc)
Nam
es must not start w
ith the letters xml (or XM
L, or Xml, etc)
N
ames cannot contain spaces
18
XML Attributes
X
ML elem
ents can have attributes in the start tag, just like HTM
L
A
ttributes are used to provide additional information about
elements.
N
o order!
S
yntax : name=‘value’ or nam
e=“value”
Forbidden Characters : ^, %
et &
P
redefined attributes :
<book tongue=“FR” date=“09/2000” id="IS
BN
-123"/>
xml:lang=“fr”
xml:id="a_unique_tag_indentifier"
xml:idref ="a_reference_tow
ards_a_tag"
example :
19
X
ML w
ith correct syntax is Well Form
ed :
X
ML docum
ents must have a root elem
ent
XM
L elements m
ust have a closing tag
XM
L tags are case sensitive
XM
L attribute values must alw
ays be quoted
X
ML elem
ents must be properly nested
Well Form
ed XM
L Docum
ent
20
Well Form
ed XM
L Docum
ent
A W
ell Formed X
ML
A
link with a style sheet is rendered possible
C
an be reused by syntactic parser/analyzer (i.e. browse the XM
L tree and transform it)
C
andidate to be a valid XM
L document
<?xm
l version = "1.0" standalone="yes"?> <!– unw
ell formed X
ML D
ocument! -->
<artist> <nam
e> Picasso
<surname>
</name> P
ablo </surnam
e> </artist>
Improperly
Nested tags
counterexample :
21
A V
alid XM
L Docum
ent
A "Valid" XML docum
ent is a "Well Form
ed" XML docum
ent, which also
conforms to the rules of a Docum
ent Type Definition (DTD) or an XML
Schema (.xsd)
D
efinition :
Conditions :
Docum
ent => Well Form
ed (syntactically correct),
Docum
ent structure conforms to the definition given in its D
TD (cf. D
TD),
R
eferences on document elem
ents can be resolved
Then
The XML docum
ent can be exchanged ! (standardized format)
-Internal: within the X
ML docum
ent not recom
mended
(using the DOCTYPE tag)
-External reuse, exchange
(a reference to a file containing the definition within the DOCTYPE tag)
22
Exercise
G
ive a Well Form
ed XM
L document w
hich represents a set of bibliographic references
If you w
ant to process these bibliographic references, w
hat would you need ?
Your first feedbacks upon X
ML ?
23
The document does not specify :
Tags : Attributes : Tag contents : - D
ata Types (i.e. String, enumeration, etc.)
First reflections on XM
L (1)
- Attribute nam
es (for each tag) - A
ttribute types (i.e. String, enumeration, etc.)
- Attribute values (i.e. Range, form
at etc.) - Tag nam
es
- constraints upon : - The order, - M
ultiplicity (no. of occurrences), - Com
position (the hierarchy). 24
First reflections on XM
L(2)
Questions : W
hen do we have to use Tags and w
hen do we have to use attributes?
How
do we indicate w
hat should be displayed/printed and how ?
D
oes Attributes order has any im
portance? N
o
Tags entities
Attributes properties
style C
SS
transformations
XSLT, DOM, XPath …
..
25
XM
L (Part II)
XM
L Docum
ent Definitions:
DTD, XM
L Schema
26
A w
ell formed and V
alid XM
L Docum
ent
W
ell Formed D
ocument
E
lements properly nested, Syntactically correct, etc.
N
ot necessarily conforms to a D
TD or X
ML S
chema
A V
alid Docum
ent
Well Form
ed + conforms to a D
TD (or a S
chema)
27
DTD
(Docum
ent Type Definition)
A DTD defines the legal elem
ents of an XM
L document
D
efines the «vocabulary» and structure of the docum
ent
A
Gram
mar w
hich phrases (instances) are X
ML docum
ents
M
ay be Internal to the document or E
xternal (referenced w
ithin an XM
L document)
28
Why use a DTD?
W
ith DTD
, each of your XM
L files can carry a description of its ow
n format w
ith it.
W
ith a DTD
, independent groups of people can agree to use a com
mon D
TD for interchanging data.
Your application can use a standard D
TD to verify
that the data you receive from the outside w
orld is valid.
Y
ou can also use a DTD
to verify your own data.
29
DTD
Contents: E
lement and A
ttribute
Elem
ents are the main building blocks of both X
ML docum
ents.
Syntax:
<!ELE
ME
NT tag (content) > O
r
<!ELE
ME
NT elem
ent-name category> (i.e. E
MP
TY, A
NY
, #PC
DA
TA)
D
efines a Tag
E.g.. : <!E
LEM
EN
T book (author, editor)>
Attributes provide extra inform
ation about elements.
Syntax
<!ATTLIS
T element-nam
e [attribute-name, attribute type #m
ode [default value]]*>
Defines the list of attributes for a given tag
E
.g. : <!ATTLIS
T author gender C
DA
TA #R
EQ
UIR
ED
city C
DA
TA #IM
PLIE
D>
<!ATTLIS
T editor city C
DA
TA #FIXE
D "P
aris">
30
Elem
ents Ordering/ S
tructuring
Elem
ent contents structuring:
(a, b) sequence e.g. (name, surnam
e, street, city)
(a | b) either / or e.g. (yes | no)
a? optional elem
ent [0,1] e.g. (name, surnam
e?, street, city)
a* zero or m
ore occurrences [0,N] e.g. (product*, custom
er)
a+ one or m
ore occurrences [1,N] e.g. (product*, seller+)
31
Data Types
C
DA
TA (C
haracter Data)
O
nly text inside a CD
ATA
section will be ignored by the parser.
P
CD
ATA
(Parsed C
haracter Data)
Text found betw
een the start tag and the end tag of an XML elem
ent.
is text that will be parsed by a parser
A
n Elem
ent with no descendants, no attributes, only text
E
numeration
A
list of values separated by « | »
ID et ID
RE
F
Key and R
eference for attributes
AN
Y
A
ny combination of parsable data
E
MP
TY
To declare E
mpty elem
ents
32
Exam
ple of an External D
TD (m
essage.dtd) <?xm
l version="1.0"?> <!D
OC
TYP
E m
essage SY
STE
M "m
essage.dtd"> <m
essage> <to>D
ave</to> <from
>Susan</from
> <subject>R
eminder</subject>
<text>Don't forget to buy m
ilk on the way hom
e.</text> </m
essage> In a separate file, "m
essage.dtd" you define your DTD
as follows:
<!ELE
ME
NT m
essage (to, from, subject, text)>
<!ELEM
EN
T to (#PC
DA
TA)>
<!ELEM
EN
T from (#P
CD
ATA)>
<!ELEM
EN
T subject (#PC
DA
TA)>
<!ELEM
EN
T text (#PC
DA
TA)>
33
Exam
ple of an Internal DTD
<?xm
l version="1.0"?> <!D
OC
TYPE
message [
<!ELE
ME
NT m
essage (to,from,subject,text)>
<!ELE
ME
NT to (#P
CD
ATA)>
<!ELEM
EN
T from (#P
CD
ATA)> <!E
LEM
EN
T subject (#PC
DATA)>
<!ELE
ME
NT text (#P
CD
ATA)> ]> <m
essage> <to>Dave</to> <from
>Susan</from>
<subject>Reminder</subject>
<text>Don't forget to buy milk on the w
ay home.</text>
</message>
34
Why encourage the use of an external D
TD?
To P
romote reusability
To share tags and structures
The D
efinition may be local or distant
<!D
OC
TYPE doc S
YSTEM
"doc.dtd">
<!DO
CTYP
E doc PU
BLIC "w
ww
.e-xmlm
edia.com/doc.dtd">
A
clear separation between a definition and its
instances
35
DTD
Entity D
eclaration
Definition: E
ntities are variables that represent other values. The value of the entity is substituted for the entity w
hen the XML docum
ent is parsed.
Entities can be defined internally or externally to your D
TD.
Syntax
Internal declaration: <!E
NTITY entity-nam
e entity-value>
E
xternal declaration: <!E
NTITY entity-nam
e SYS
TEM
"entity-UR
L">
To use it &
entity-name
Exam
ple (internal): <!E
NTITY w
ebsite "http://ww
w.TheS
carms.com
">
Exam
ple (external): <!E
NTITY w
ebsite SYS
TEM
"http://ww
w.TheS
carms.com
/entity.xml">
The above entity make this line of XM
L valid.
XML line:
<url>&w
ebsite</url> E
valuates to: <url>http://w
ww
.TheScarm
s.com</url>
36
DTD
: Sum
mary
D
efines the document structure w
ith a list of legal elements
D
TD Building blocks : E
LEME
NT, ATTLIST, E
NTITY, P
CD
ATA, C
DA
TA;
E
LEME
NT
•
Sim
ple :
•C
omposition :
•O
ccurrence Multiplicity :
- Sequence of elements ordered List
(a, b, c) - Alternatives choices
(a | b | c) - M
ix
(a, (b | c), d)
? (zero or one) ), * (zero or m
ore), + (one or m
ore)
- empty (EM
PTY) - N
o constraints on type (ANY), - text (#PCDATA
)
37
Exercise
P
ropose a DTD
that allows the definition of XM
L docum
ents representing a Catalog of Products
(products, description, price, etc).
G
ive an example of an X
ML D
ocuments that
conforms to the D
TD you propose
C
ould you provide some advantages, draw
backs of using D
TD.
38
The Catalog D
TD
<!DO
CTYP
E C
ATA
LOG
[ <!E
LEM
EN
T CA
TALO
G (P
RO
DU
CT+)>
<!ELE
ME
NT P
RO
DU
CT (S
PE
CIFIC
ATIO
NS
+, OP
TION
S?, P
RIC
E+, N
OTE
S?)>
<!ELE
ME
NT S
PE
CIFIC
ATIO
NS
(#PC
DA
TA)>
<!ELEM
EN
T OPTIO
NS
(#PCD
ATA
)> <!E
LEM
EN
T PR
ICE
(#PC
DA
TA)>
<!ELE
ME
NT N
OTE
S (#P
CD
ATA
)> <!A
TTLIST P
RO
DU
CT N
AM
E C
DA
TA #IM
PLIE
D
C
ATE
GO
RY (H
andTool | Table | Shop-P
rofessional) "HandTool"
P
AR
TNU
M C
DA
TA #IM
PLIE
D
PLAN
T (Pittsburgh | M
ilwaukee | C
hicago) "Chicago“
IN
VE
NTO
RY (InS
tock | Backordered | D
iscontinued) "InStock">
<!ATTLIS
T SP
EC
IFICA
TION
S W
EIG
HT C
DA
TA #IM
PLIE
D
PO
WE
R C
DA
TA #IM
PLIE
D>
<!ATTLIS
T OP
TION
S FIN
ISH
(Metal | P
olished | Matte) "M
atte"
AD
AP
TER
(Included | Optional | N
otApplicable) "Included"
C
AS
E (HardS
hell | Soft | N
otApplicable) "H
ardShell">
<!ATTLIS
T PR
ICE
MS
RP
CD
ATA
#IMP
LIED
W
HO
LES
ALE
CD
ATA
#IMP
LIED
S
TRE
ET C
DA
TA #IM
PLIE
D
SH
IPP
ING
CD
ATA
#IMP
LIED
> <!E
NTITY A
UTH
OR
"John Doe">
<!EN
TITY CO
MP
AN
Y "JD P
ower Tools, Inc.">
<!EN
TITY EM
AIL "jd@
jd-tools.com"> ]>
39
DTD
: Draw
backs
W
eak Data Typing
B
asically one data type: Text (String)
A
re not Object O
riented (No Inheritance )
Specific language: N
o XM
L-Based
H
ard to parse/interpret
Proposition to overcom
e these limitations:
W
3C's XML-Schem
a
40
XM
L Schem
a
XM
L Schem
a is an XM
L-based alternative to DTD
.
The XM
L Schem
a language is also referred to as XM
L Schem
a D
efinition (XSD
).
A
n XM
L Schem
a describes the structure of an XM
L document :
D
ocument's possible elem
ents
Element attributes and their type
XM
L Schem
as use XM
L Syntax
N
o new language as for the D
TD
XM
L Schem
as support many D
ata Types
M
ore advantages
Data Structures and rich data typing
extensibility thanks to inheritance
analyzable by standard X
ML parsers
41
The root element of an X
ML S
chema
The <schem
a> element is the root elem
ent of every XM
L S
chema:
<?xm
l version="1.0"?> <xs:schem
a> //schem
a body... //...
</xs:schema>
The <schem
a> element m
ay contain some attributes. A
schema declaration often looks som
ething like this: <?xm
l version="1.0"?> <xs:schem
a xmlns:xs="http://w
ww
.w3.org/2001/XM
LSchema">
//...
//...
</xs:schema>
42
XS
D, H
ow to?
R
eference a Schem
a in an XM
L Docum
ent: <?xm
l version="1.0"?> <note xm
lns:xsi="http://ww
w.w
3.org/2001/XM
LSchema-
instance" xsi:schemaLocation="path_to_your_file.xsd">
<to>Tove</to> <from
>Jani</from>
<heading>Rem
inder</heading> <body>D
on't forget me this w
eekend!</body> </note>
Your docum
ent Root tag
43
XS
D, H
ow to?
D
efine a Simple Elem
ent
A
n XML elem
ent that can contain only text (typed data).
It cannot contain any other elements or attributes
Syntax: <xs:elem
ent name="xxx" type="yyy"/>
E.g.
An X
ML D
ocument (a chunk):
<lastnam
e>Refsnes</lastnam
e> <age>36</age> <dateborn>1970-03-27</dateborn>
The C
orresponding simple elem
ent definition in the XM
L Schem
a <xs:elem
ent name="lastnam
e" type="xs:string"/> <xs:elem
ent name="age" type="xs:integer"/>
<xs:element nam
e="dateborn" type="xs:date"/>
Also:
<xs:elem
ent name="color" type="xs:string" default="red"/> (if no value)
Or
<xs:elem
ent name="color" type="xs:string" fixed="red"/> (can't be m
odified)
44
XS
D, H
ow to?
D
efine XSD
Attributes
All attributes are declared as sim
ple types
If an element has attributes, it is considered as a com
plex type
Syntax: <xs:attribute nam
e="xxx" type="yyy"/> E
.g. <xs:attribute nam
e="language" type="xs:string"/>
Also:
<xs:attribute name="lang" type="xs:string" default="E
N"/> (if no value,
use default)
<xs:attribute name="lang" type="xs:string" fixed="E
N"/> (can't be
modified)
A
ttributes are optional by default. To specify that the attribute is required, use the "use" property:
<xs:attribute nam
e="lang" type="xs:string" use="required"/>
45
Basic types (1) Type
Description
string represents a String
boolean A Boolean value: true or false.
decimal
represents a decimal
float represents a float.
double represents a double.
duration represents a duration
dateTime
represents a value: date/time.
time
(format : hh:m
m:ss.sss ).
date represents a date (form
at : CCYY-M
M-D
D).
gYearMonth
represents Gregorian year and m
onth (format : CCYY-M
M)
46
Basic types (2)
Type Description
gYear represents a year (form
at : CCYY).
gMonthD
ay represents m
onth's day (format : M
M-D
D)
gDay
represents a day (format : D
D).
gMonth
represents a month (form
at : MM
).
hexBinary represents a binary hexadecim
al content.
base64Binary represents a 64 base binary content
anyUR
I represents U
RI address (ex.: http://www.site.com).
NO
TATION
represents a qualified nam
e.
47
Basic types (3)
Type Description
token represents a string w
ithout line feeds, carriage returns, tabs, leading and trailing spaces, and m
ultiple spaces language
represents a string that contains a valid language id N
MTO
KEN
a string that represents the NMTO
KEN attribute in XM
L (only used with schem
a attributes) id
a string that represents the ID attribute in XM
L (only used with schem
a attributes) ID
REF, ID
REFS
represents attributes IDREF, ID
REFS type
ENTITY, EN
TITIES represents the types: ENTITY, ENTITIES
integer represents an integer value (signed, arbitrary length)
nonPositiveInteger an integer containing only non-positive values (.., -2, -1, 0)
negativeInteger An integer containing only negative values ( .., -2, -1.)
48
Basic types (4)
Type Description
long Long integer between {-9223372036854775808 - 223372036854775807}
int A signed 32-bit integer between {-2147483648 - 2147483647}
short Short Integer {-32768 - 32767}
byte Between {-128 - 127}
nonNegativeInteger
An integer containing only non-negative values (0, 1, 2, ..) unsignedLong
An unsigned 64-bit integer long
A signed 64-bit integer {0 - 18446744073709551615} unsignedInt
An unsigned 32-bit integer {0 - 4294967295}
unsignedShort An unsigned 16-bit integer {0 - 65535}
unsignedByte An unsigned 8-bit integer {0 - 255}
positiveInteger An integer containing only positive values (1, 2, ..)
49
XS
D Com
plex Elements
A
complex elem
ent contains other elements and/or
attributes
four kinds of com
plex elements:
em
pty elements
elem
ents that contain only other elements
elem
ents that contain attributes and only text
elements that contain both other elem
ents and text
Note: E
ach of these elements m
ay contain attributes as w
ell!
50
XS
D, H
ow to?
Define a Com
plex Element in XM
L Schema
tw
o different ways :
E
.g.: somew
here in a XM
L document you have for instance:
<em
ployee> // a com
plex Element that contains only other elem
ents
<firstname>John</firstnam
e>
<lastname>Sm
ith</lastname>
</em
ployee> First possible XM
L Schema:
<xs:elem
ent name="em
ployee">
<xs:com
plexType>
<xs:sequence>
<xs:element nam
e="firstname" type="xs:string"/>
<xs:element nam
e="lastname" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
51
XS
D, H
ow to?
Define a Com
plex Element in XM
L Schema
E
.g.: somew
here in a XM
L document you have for instance:
<em
ployee>
<firstname>John</firstnam
e>
<lastname>S
mith</lastnam
e>
</employee>
Second possible XML Schem
a: <xs:elem
ent name="em
ployee" type="personinfo"/> //…
…
//……
<xs:com
plexType name="personinfo">
<xs:sequence>
<xs:element nam
e="firstname" type="xs:string"/>
<xs:element nam
e="lastname" type="xs:string"/>
</xs:sequence> </xs:com
plexType>
If you use the second w
ay (above), several elements can refer to the sam
e complex type as
being their typed
E.g.
<xs:element nam
e="employee" type="personinfo"/>
<xs:element nam
e="student" type="personinfo"/> <xs:elem
ent name="m
ember" type="personinfo"/>
52
XS
D, H
ow to?
Define Com
plex Text-Only Elem
ents
contains only simple content (text and attributes),
we add a sim
pleContent elem
ent around the content.
E.g.
<shoesize country="france">35</shoesize>
The corresponding XML Schem
a: <xs:elem
ent name="shoesize">
<xs:complexType>
<xs:simpleContent> // to indicate that it does not contain other elem
ents <xs:extension base="xs:integer"> // to indicate the text type <xs:attribute nam
e="country" type="xs:string" /> // the attribute type </xs:extension> </xs:sim
pleContent> </xs:com
plexType> </xs:elem
ent>
53
XS
D, H
ow to?
Define Com
plex Types with M
ixed Content
A m
ixed complex type elem
ent can contain attributes, elements, and text.
E
.g. <letter> D
ear Mr.
<nam
e>John Sm
ith</name>. Your order <orderid>1032</orderid> w
ill be shipped on <shipdate>2001-07-13</shipdate>
</letter> The corresponding XM
L Schema:
<xs:element nam
e="letter"> <xs:com
plexType mixed="true">
<xs:sequence> <xs:elem
ent name="nam
e" type="xs:string"/> <xs:elem
ent name="orderid" type="xs:positiveInteger"/>
<xs:element nam
e="shipdate" type="xs:date"/> </xs:sequence> </xs:com
plexType> </xs:elem
ent>
54
XS
D Indicators
Indicators control HO
W elem
ents have to be used in docum
ents
Order indicators:
All
specifies that the child elements can appear in any order
each child elem
ent must occur only once
E
.g.: <xs:elem
ent name="person">
<xs:complexType>
<xs:all> <xs:elem
ent name="firstnam
e" type="xs:string"/> <xs:elem
ent name="lastnam
e" type="xs:string"/> </xs:all> </xs:com
plexType> </xs:elem
ent>
55
XS
D Indicators
O
rder indicators:
Sequence
specifies that the child elements m
ust appear in a specific order
E.g.:
<xs:element nam
e="person"> <xs:com
plexType> <xs:sequence> <xs:elem
ent name="firstnam
e" type="xs:string"/> <xs:elem
ent name="lastnam
e" type="xs:string"/> </xs:sequence> </xs:com
plexType> </xs:elem
ent>
56
XS
D Indicators
O
rder indicators:
Choice
specifies that either one child element or another can occur
E
.g.: <xs:elem
ent name="person">
<xs:complexType>
<xs:choice> <xs:elem
ent name="em
ployee" type="employee"/>
<xs:element nam
e="mem
ber" type="mem
ber"/> </xs:choice> </xs:com
plexType> </xs:elem
ent>
57
XS
D Indicators
O
ccurrence indicators:
Occurrence indicators are used to define how
often an element can
occur
maxO
ccurs: the maxim
um num
ber of times an elem
ent can occur:
minO
ccurs : the minim
um num
ber of times an elem
ent can occur
E.g.:
<xs:element nam
e="person"> <xs:com
plexType> <xs:sequence>
<xs:element nam
e="full_name" type="xs:string"/>
<xs:elem
ent name="child_nam
e" type="xs:string"
m
axOccurs="10" m
inOccurs="0"/>
</xs:sequence>
</xs:complexType>
</xs:element>
58
XML Schem
a extension Element
The extension elem
ent extends an existing simpleType
or complexType elem
ent.
Parent enclosing elements: sim
pleContent O
r complexContent
<xs:complexType nam
e="fullpersoninfo"> <xs:com
plexContent>
<xs:extension base="personinfo"> <xs:sequence> <xs:elem
ent name="address" type="xs:string"/>
<xs:element nam
e="city" type="xs:string"/> <xs:elem
ent name="country" type="xs:string"/>
</xs:sequence> </xs:extension> </xs:com
plexContent>
</xs:complexType>
</xs:schema>
<xs:complexType nam
e="personinfo"> <xs:sequence> <xs:elem
ent name="firstnam
e" type="xs:string"/> <xs:elem
ent name="lastnam
e" type="xs:string"/> </xs:sequence> </xs:com
plexType>
59
XML Schem
a Restrictions R
estrictions are used to define acceptable values for X
ML elem
ents or attribute .
Parent enclosing elements: sim
pleType E
.g.: <xs:elem
ent name="car">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="A
udi"/>
<xs:enum
eration value="Golf"/>
<xs:enumeration value="B
MW
"/>
</xs:restriction> </xs:sim
pleType> </xs:elem
ent>
60
XML Schem
a Restrictions C
onstraint D
escription enum
eration D
efines a list of acceptable values fractionD
igits Specifies the m
aximum
number of decim
al places allowed. M
ust be equal to or greater than zero length
Specifies the exact number of characters or list item
s allowed. M
ust be equal to or greater than zero m
axExclusive Specifies the upper bounds for num
eric values (the value must be less than this value)
maxInclusive
Specifies the upper bounds for numeric values (the value m
ust be less than or equal to this value) m
axLength Specifies the m
aximum
number of characters or list item
s allowed. M
ust be equal to or greater than zero m
inExclusive Specifies the low
er bounds for numeric values (the value m
ust be greater than this value) m
inInclusive Specifies the low
er bounds for numeric values (the value m
ust be greater than or equal to this value) m
inLength Specifies the m
inimum
number of characters or list item
s allowed. M
ust be equal to or greater than zero
pattern D
efines the exact sequence of characters that are acceptable totalD
igits Specifies the exact num
ber of digits allowed. M
ust be greater than zero w
hiteSpace Specifies how
white space (line feeds, tabs, spaces, and carriage returns) is handled
Restrictions for D
ata types
61
XM
L Schem
a Patterns
C
onstraints on values of basic types
With use of R
egular Expressions
Exam
ple <xs:elem
ent name="letter">
<xs:simpleType>
<xs:restriction base="xs:string"> <xs:pattern value="([a-z])*"/> </xs:restriction> </xs:sim
pleType> </xs:elem
ent>
/* The acceptable value is zero or m
ore occurrences of low
ercase letters from a to z */
62
XM
L Schem
a : example (1)
<xsd:schema xm
lns:xsd="http://ww
w.w
3.org/1999/XM
LSchema">
<xsd:element nam
e="purchaseOrder" type="PurchaseO
rderType"/> <xsd:elem
ent name="com
ment" type="xsd:string"/>
<xsd:complexType nam
e="PurchaseOrderType">
<xsd:sequence>
<xsd:element nam
e="shipTo" type="USA
ddress"/>
<xsd:elem
ent name="billTo" type="U
SAddress"/>
<xsd:element ref="com
ment" m
inOccurs="0"/>
<xsd:element nam
e="items" type="Item
s"/>
</xsd:sequence>
<xsd:attribute name="orderD
ate" type="xsd:date"/> </xsd:com
plexType>
63
XM
L Schem
a : example (2)
<xsd:complexType nam
e="Items">
<xsd:sequence>
<xsd:elem
ent name="item
" minO
ccurs="0" maxO
ccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element nam
e="productNam
e" type="xsd:string"/>
<xsd:element nam
e="quantity">
<xsd:sim
pleType>
<xsd:restriction base="xsd:positiveInteger">
<xsd:maxExclusive value="100"/>
</xsd:restriction>
</xsd:sim
pleType>
</xsd:element>
<xsd:elem
ent name="U
SPrice" type="xsd:decimal"/>
<xsd:elem
ent ref="comm
ent" minO
ccurs="0"/>
<xsd:element nam
e="shipDate" type="xsd:date" m
inOccurs="0"/>
</xsd:sequence>
<xsd:attribute nam
e="partNum
" type="SKU
" use="required"/>
</xsd:complexType>
</xsd:elem
ent>
</xsd:sequence> </xsd:com
plexType> </xsd:schem
a>
64
Som
e XM
L Tools Editor
Tool Support
Tibco (Extensibility)
XM
L Authority 2.0
DTD
S
chema
Altova
XM
L Spy (2007
available:1 month trial)
DTD
S
chema
Dasan
Tagfree 2000 DTD
E
ditor D
TD
Data Junction
XM
L Junction S
chema
Insight Soft.
XM
LMate 2.0
DTD
S
chema
Microstar Soft.
Near &
Far Designer
DTD
65
Exercise
G
ive the XM
L schema of w
hat could an address book
G
ive an example of an X
ML docum
ent that contains a list of contacts and that conform
s to the schem
a you proposed
Your feedbacks ?
66
XM
L Schem
a, summ
ary
Expressive and extensible
R
ich data typing
More and m
ore used
Model exchange: X
MI 2.0
W
eb Services: S
OA
P, WS
DL
…
A
bit too complex!
67
XM
L : Wrap-up (P
art I, II)
M
eta-language ! Infinite number of :
A
tree-like structure !
S
eparation :
Form
alization :
A
standard and bunch of tools available for XM
L developers
- tags and, - Their associated attributes
- Data
(.xml)
- Logical syntax (.dtd or .xsd)
- Well-form
ed documents (correct XM
L syntax) - valid (well form
ed and conforms to a DTD or XSD)
Recommended
