16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
67 lines
1.9 KiB
Plaintext
67 lines
1.9 KiB
Plaintext
== Why is this an issue?
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Complex types can be restricted by means of an ``++xs:restriction++`` element. But ``++restriction++`` is anti-inheritance: the derived type has less information than the base type. Further, restriction causes the redefinition of the complex types elements and attributes, which leads to fragility in your XML schema; any change to a super type will require corresponding changes in all restricting subtypes, even those in other schemas. For example, if the base type defines a mandatory "color" element of type ``++xs:int++``, the restricting type must also define a "color" element whose type cannot be, say, ``++xs:string++``.
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``++xs:extension++``, on the other hand, allows the extending element to inherit the base class' elements and add new ones.
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=== Noncompliant code example
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[source,xml]
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----
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<xs:complexType name="Fruit>
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<xs:sequence>
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<xs:element name="name" type="xs:string"/>
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<xs:element name="color" type="xs:string" minOccurs="0"/>
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</xs:sequence>
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</xs:complexType>
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<xs:complexType name="UncoloredFruit">
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<xs:complexContent>
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<xs:restriction base="Fruit"> <!-- Noncompliant -->
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<xs:sequence>
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<xs:element name="name" type="xs:string"/>
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</xs:sequence>
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</xs:restriction>
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</xs:complexContent>
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</xs:complexType>
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----
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=== Compliant solution
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[source,xml]
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----
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<xs:complexType name="FruitBase>
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<xs:sequence>
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<xs:element name="name" type="xs:string"/>
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</xs:sequence>
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</xs:complexType>
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<xs:complexType name="ColoredFruit>
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<xs:sequence>
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<!-- Bottom-up design, using aggregation -->
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<xs:element name="base" type="FruitBase"/>
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<xs:element name="color" type="xs:string" minOccurs="0"/>
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</xs:sequence>
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</xs:complexType>
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Remove this "restriction", and consider "extension" instead.
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=== Highlighting
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``++xs:restriction++``
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endif::env-github,rspecator-view[]
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