Definitive XML Schema: Table of Contents

Definitive XML Schema

Priscilla Walmsley (pwalmsley@datypic.com)
1st edition (December 7, 2001)
Prentice Hall PTR; ISBN: 0130655678

Chapter 1: Schemas: An introduction	2
1.1 What is an XML schema?	3
1.2 The purpose of schemas	4
1.2.1 Data validation	4
1.2.2 A contract with trading partners	5
1.2.3 System documentation	5
1.2.4 Augmentation of data	5
1.2.5 Application information	5
1.3 Schema design	6
1.3.1 Accuracy and precision	7
1.3.2 Clarity	7
1.3.3 Broad applicability	7
1.4 Schema languages	8
1.4.1 Document Type Definitions (DTDs)	8
1.4.2 Enter schemas	9
1.4.3 W3C XML Schema	9
1.4.4 Notes on terminology	10
1.4.4.1 Schema	10
1.4.4.2 Type	11
1.4.5 Additional schema languages	11
1.4.5.1 RELAX NG	11
1.4.5.2 Schematron	13

Chapter 2: A quick tour of XML Schema	16
2.1 An example schema	17
2.2 The components of XML Schema	18
2.2.1 Declarations vs. definitions	18
2.2.2 Global vs. local components	19
2.3 Elements and attributes	20
2.3.1 The tag/type distinction	20
2.4 Data types	21
2.4.1 Simple vs. complex types	21
2.4.2 Named vs. anonymous types	22
2.4.3 The type definition hierarchy	22
2.5 Simple types	23
2.5.1 Built-in simple types	23
2.5.2 Restricting simple types	24
2.5.3 List and union types	24
2.6 Complex types	25
2.6.1 Content types	25
2.6.2 Content models	26
2.6.3 Deriving complex types	27
2.7 Namespaces and XML Schema	28
2.8 Schema composition	30
2.9 Instances and schemas	30
2.10 Annotations	32
2.11 Advanced features	32
2.11.1 Reusable groups	33
2.11.2 Identity constraints	33
2.11.3 Substitution groups	33
2.11.4 Redefinition	33

Chapter 3: Namespaces	36
3.1 Namespaces in XML	37
3.1.1 Namespace names are URIs	38
3.1.2 Namespace declarations and prefixes	39
3.1.3 Default namespace declarations	41
3.1.4 Name terminology	42
3.1.5 Scope of namespace declarations	43
3.1.6 Overriding namespace declarations	43
3.1.7 Attributes and namespaces	45
3.1.8 A summary example	46
3.2 The relationship between namespaces and schemas	47
3.3 Using namespaces in XSDL	49
3.3.1 Target namespaces	49
3.3.2 The XML Schema Namespace	50
3.3.3 The XML Schema Instance Namespace	51
3.3.4 Namespace declarations in schema documents	51
3.3.4.1 Map a prefix to the XML Schema Namespace	51
3.3.4.2 Map a prefix to the target namespace	53
3.3.4.3 Map a prefix to all namespaces	53

Chapter 4: Schema composition	56
4.1 Modularizing schema documents	57
4.2 Defining schema documents	59
4.2.1 Defining a schema document in XSDL	59
4.3 Schema assembly	60
4.3.1 Assembling schemas from multiple documents	60
4.3.2 Uniqueness of qualified names	62
4.3.3 Missing components	63
4.3.4 Schema document defaults	64
4.4 include, redefine, and import	65
4.4.1 include	65
4.4.2 redefine	69
4.4.3 import	70

Chapter 5: Instances and schemas	74
5.1 Using the instance attributes	75
5.2 Schema processing	77
5.2.1 Validation	77
5.2.2 Augmenting the instance	78
5.3 Relating instances to schemas	79
5.4 Using XSDL hints in the instance	80
5.4.1 The xsi:schemaLocation attribute	80
5.4.2 The xsi:noNamespaceSchemaLocation attribute	82
5.5 Dereferencing namespaces	83
5.6 The root element	84
5.7 Using DTDs and schemas together	87
5.8 Using specific schema processors	88
5.8.1 XSV	89
5.8.2 Xerces	90
5.8.3 Oracle XDK	92
5.8.4 Microsoft MSXML	93

Chapter 6: Schema documentation and extension	96
6.1 The mechanics	97
6.1.1 Annotations	97
6.1.2 User documentation	98
6.1.3 Application information	100
6.1.4 Validating annotations	101
6.1.5 Non-native attributes	103
6.1.6 Design hint: Should I use annotations or non-native attributes?	104
6.2 User documentation	104
6.2.1 Types of user documentation	104
6.2.2 Data element definitions	105
6.2.3 Code documentation	106
6.2.4 Section comments	106
6.3 Application information	108
6.3.1 Types of application information	108
6.3.2 Schematron for co-occurrence constraints	108
6.3.3 Schema adjunct framework for RDBMS mappings	111
6.4 Notations	111
6.4.1 Declaring a notation	113
6.4.2 Declaring a notation attribute	113
6.4.3 Notations and unparsed entities	116

Chapter 7: Element declarations	118
7.1 Global and local element declarations	119
7.1.1 Global element declarations	119
7.1.2 Local element declarations	123
7.1.3 Design hint: Should I use global or local element declarations?	125
7.2 Declaring the data types of elements	126
7.3 Default and fixed values	128
7.3.1 Default values	129
7.3.2 Fixed values	131
7.4 Nils and nillability	132
7.4.1 Using xsi:nil in an instance	136
7.4.2 Making elements nillable	136
7.5 Qualified vs. unqualified forms	137

Chapter 8: Attribute declarations	140
8.1 Global and local attribute declarations	141
8.1.1 Design hint: Should I use attributes or elements?	142
8.1.2 Global attribute declarations	143
8.1.3 Local attribute declarations	145
8.1.4 Design hint: Should I declare attributes globally or locally?	147
8.2 Assigning types to attributes	148
8.3 Default and fixed values	149
8.3.1 Default values	150
8.3.2 Fixed values	151
8.4 Qualified vs. unqualified forms	152

Chapter 9: Simple types	154
9.1 Simple type varieties	155
9.1.1 Design hint: How much should I break down my data values?	156
9.2 Simple type definitions	157
9.2.1 Named simple types	157
9.2.2 Anonymous simple types	158
9.2.3 Design hint: Should I use named or anonymous types?	159
9.3 Simple type restrictions	161
9.3.1 Defining a restriction	162
9.3.2 Overview of the facets	163
9.3.3 Inheriting and restricting facets	164
9.3.4 Fixed facets	166
9.3.4.1 Design hint: When should I fix a facet?	167
9.4 Facets	168
9.4.1 Bounds facets	168
9.4.2 Length facets	169
9.4.2.1 Design hint: What if I want to allow empty values?	169
9.4.2.2 Design hint: What if I want to restrict the length of an integer?	170
9.4.3 totalDigits and fractionDigits	171
9.4.4 Enumeration	171
9.4.5 Pattern	173
9.4.6 Whitespace	176
9.5 Preventing simple type derivation	177

Chapter 10: Regular expressions	180
10.1 The structure of a regular expression	181
10.2 Atoms	183
10.2.1 Normal characters	184
10.2.2 Character class escapes	185
10.2.2.1 Single-character escapes	186
10.2.2.2 Multi-character escapes	186
10.2.2.3 Category escapes	188
10.2.2.4 Block escapes	190
10.2.3 Character class expressions	195
10.2.3.1 Specifying a list of characters	195
10.2.3.2 Specifying a range	196
10.2.3.3 Combining characters and ranges	196
10.2.3.4 Negating a character class expression	197
10.2.3.5 Subtracting from a character class expression	197
10.2.4 Parenthesized regular expressions	198
10.3 Quantifiers	198

Chapter 11: Union and list types	202
11.1 Varieties and derivation types	203
11.2 Union types	205
11.2.1 Defining union types	205
11.2.2 Restricting union types	207
11.2.3 Unions of unions	208
11.2.4 Specifying the member type in the instance	208
11.3 List types	209
11.3.1 Defining list types	209
11.3.2 Design hint: When should I use lists?	211
11.3.3 Restricting list types	212
11.3.3.1 Length facets	212
11.3.3.2 Enumeration facet	214
11.3.3.3 Pattern facet	215
11.3.4 Lists and strings	216
11.3.5 Lists of unions	217
11.3.6 Lists of lists	218
11.3.7 Restricting the item type	219

Chapter 12: Built-in simple types	220
12.1 Built-in types	221
12.2 String-based types	223
12.2.1 string, normalizedString, and token	223
12.2.1.1 Design hint: Should I use string, normalizedString, or token?	225
12.2.2 Name	227
12.2.3 NCName	227
12.2.4 language	228
12.3 Numeric types	231
12.3.1 float and double	231
12.3.2 decimal	231
12.3.3 Integer types	233
12.3.3.1 Design hint: Is it an integer or a string?	234
12.4 Date and time types	237
12.4.1 date	237
12.4.2 time	238
12.4.3 dateTime	239
12.4.4 gYear	239
12.4.5 gYearMonth	240
12.4.6 gMonth	242
12.4.7 gMonthDay	242
12.4.8 gDay	243
12.4.9 duration	244
12.4.10 Representing time zones	245
12.4.11 Facets	246
12.4.12 Date and time ordering	247
12.5 Legacy types	247
12.5.1 ID	247
12.5.2 IDREF	249
12.5.3 IDREFS	250
12.5.4 ENTITY	251
12.5.5 ENTITIES	252
12.5.6 NMTOKEN	254
12.5.7 NMTOKENS	255
12.5.8 NOTATION	256
12.6 Other types	256
12.6.1 QName	256
12.6.2 boolean	258
12.6.3 hexBinary and base64Binary	259
12.6.4 anyURI	259
12.7 Type equality	262

Chapter 13: Complex types	266
13.1 What are complex types?	267
13.2 Defining complex types	268
13.2.1 Named complex types	268
13.2.2 Anonymous complex types	270
13.2.3 Complex type alternatives	271
13.3 Content types	272
13.3.1 Simple content	272
13.3.2 Element-only content	273
13.3.3 Mixed content	273
13.3.4 Empty content	275
13.4 Using element types	275
13.4.1 Local element declarations	276
13.4.2 Element references	276
13.4.3 Element wildcards	278
13.4.4 Duplication of element-type names	281
13.5 Using model groups	283
13.5.1 sequence groups	283
13.5.1.1 Design hint: Should I care about the order of elements?	285
13.5.2 choice groups	286
13.5.3 Nesting of sequence and choice groups	288
13.5.4 all groups	289
13.5.5 Named model group references	290
13.5.6 Deterministic content models	291
13.6 Using attributes	293
13.6.1 Local attribute declarations	293
13.6.2 Attribute references	294
13.6.3 Attribute wildcards	296
13.6.4 Attribute group references	297

Chapter 14: Deriving complex types	300
14.1 Why derive types?	301
14.2 Restriction and extension	302
14.3 Simple content and complex content	303
14.3.1 simpleContent elements	303
14.3.2 complexContent elements	303
14.4 Complex type extensions	305
14.4.1 Simple content extensions	306
14.4.2 Complex content extensions	306
14.4.2.1 Extending choice groups	309
14.4.3 Mixed content extensions	310
14.4.4 Empty content extensions	310
14.4.5 Attribute extensions	311
14.4.6 Attribute wildcard extensions	312
14.5 Complex type restrictions	314
14.5.1 Simple content restrictions	315
14.5.2 Complex content restrictions	317
14.5.2.1 Eliminating meaningless groups	319
14.5.2.2 Restricting element declarations	319
14.5.2.3 Restricting wildcards	321
14.5.2.4 Restricting groups	322
14.5.3 Mixed content restrictions	327
14.5.4 Empty content restrictions	329
14.5.5 Attribute restrictions	330
14.5.6 Attribute wildcard restrictions	331
14.6 Type substitution	334
14.7 Controlling type derivation and substitution	335
14.7.1 final: Preventing complex type derivation	336
14.7.2 block: Blocking substitution of derived types	336
14.7.3 Blocking type substitution in element declarations	338
14.7.4 abstract: Forcing derivation	339

Chapter 15: Reusable groups	342
15.1 Why reusable groups?	343
15.2 Named model groups	344
15.2.1 Defining named model groups	344
15.2.2 Referencing named model groups	346
15.2.2.1 Group references	347
15.2.2.2 Referencing a named model group in a complex type	347
15.2.2.3 Using all in named model groups	349
15.2.2.4 Named model groups referencing named model groups	349
15.3 Attribute groups	351
15.3.1 Defining attribute groups	351
15.3.2 Referencing attribute groups	353
15.3.2.1 Attribute group references	353
15.3.2.2 Referencing attribute groups in complex types	354
15.3.2.3 Duplicate attribute names	355
15.3.2.4 Duplicate attribute wildcard handling	355
15.3.2.5 Attribute groups referencing attribute groups	356
15.4 Reusable groups vs. complex type derivations	357

Chapter 16: Substitution groups	360
16.1 Why substitution groups?	361
16.2 The substitution group hierarchy	362
16.3 Declaring a substitution group	363
16.4 Type constraints for substitution groups	365
16.5 Alternatives to substitution groups	367
16.5.1 Reusable choice groups	367
16.5.2 Substituting a derived type in the instance	369
16.6 Controlling substitution groups	371
16.6.1 final: Preventing substitution group declarations	371
16.6.2 block: Blocking substitution in instances	373
16.6.3 abstract: Forcing substitution	373

Chapter 17: Identity constraints	376
17.1 Identity constraint categories	377
17.2 Design hint: Should I use ID/IDREF or key/keyref?	378
17.3 Structure of an identity constraint	378
17.4 Uniqueness constraints	380
17.5 Key constraints	382
17.6 Key references	383
17.6.1 Key references and type equality	386
17.7 Selectors and fields	387
17.7.1 Selectors	387
17.7.2 Fields	387
17.8 The XML Schema XPath subset	388
17.9 Identity constraints and namespaces	390

Chapter 18: Redefining schema components	396
18.1 Redefinition basics	397
18.1.1 Include plus redefine	399
18.1.2 Redefine and namespaces	399
18.1.3 Pervasive impact	399
18.2 The mechanics of redefinition	400
18.3 Redefining simple types	401
18.4 Redefining complex types	402
18.5 Redefining named model groups	404
18.5.1 Defining a subset	405
18.5.2 Defining a superset	406
18.6 Redefining attribute groups	407
18.6.1 Defining a subset	407
18.6.2 Defining a superset	409

Chapter 19: Topics for DTD users	412
19.1 Element declarations	413
19.1.1 Simple types	413
19.1.2 Complex types with simple content	415
19.1.3 Complex types with complex content	415
19.1.4 Mixed content	418
19.1.5 Empty content	419
19.1.6 Any content	420
19.2 Attribute declarations	420
19.2.1 Attribute types	420
19.2.2 Enumerated attribute types	421
19.2.3 Notation attributes	422
19.2.4 Default values	422
19.3 Notations	423
19.4 Parameter entities for reuse	424
19.4.1 Reusing content models	424
19.4.2 Reusing attributes	425
19.5 Parameter entities for extensibility	425
19.5.1 Extensions for sequence groups	426
19.5.2 Extensions for choice groups	428
19.5.3 Attribute extensions	430
19.5.4 Attribute group extensions	430
19.6 External parameter entities	431
19.7 General entities	433
19.7.1 Character and other parsed entities	433
19.7.2 Unparsed entities	433
19.8 Comments	434
19.9 Using DTDs and schemas together	436

Chapter 20: Naming considerations	438
20.1 Naming guidelines	439
20.1.1 Rules for valid XML names	440
20.1.2 Separators	440
20.1.3 Name length	441
20.1.4 Standard terms and abbreviations	441
20.1.5 Use of subject terms	441
20.2 Qualified vs. unqualified names	444
20.2.1 Qualified local names	444
20.2.2 Unqualified local names	445
20.2.3 Using elementFormDefault	445
20.2.4 Form and global element declarations	447
20.2.5 Default namespaces and unqualified names	447
20.2.6 Design hint: Should I use qualified or unqualified local names?	448
20.2.7 Qualified vs. unqualified attribute names	449
20.3 Structuring namespaces	450
20.3.1 Same namespace	451
20.3.2 Different namespaces	453
20.3.3 Chameleon namespaces	458
20.4 Multiple languages	460

Chapter 21: Extensibility and reuse	464
21.1 Reuse	466
21.2 Extending schemas	467
21.2.1 Wildcards	468
21.2.2 Type derivation	471
21.2.3 Substitution groups	473
21.2.4 Type redefinition	475
21.2.5 Named model group redefinition	477
21.3 Versioning of schemas	478
21.3.1 Schema compatibility	479
21.3.2 Application compatibility	480
21.3.3 Conversion capability	481
21.3.4 Using version numbers	481
21.4 Designing applications to support change	482

Appendix A: Table of XSDL keywords	484
A.1 XSDL element types	485
A.2 XSDL attributes	494

Appendix B: Built-in simple types	504
B.1 Built-in simple types	505

Index	511