Dev:Syntactic Guidelines

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Newly created files

Byte order mark (BOM)

For more information about the "Byte Order Mark" see Wikipedia: Byte Order Mark (BOM)

As recommended by the W3C, an UTF-8 encoded file should not start with an BOM for less troubles with editors and browsers, see also W3C Recommandation about BOM

Visualization tip for BOM (command line tool): less $FILENAME$

<U+FEFF><?xml version="1.0" encoding="UTF-8"?>

Subversion properties and keywords

see Subversion Guidelines for new files

Camel Case

Always use camel case for all names. Don't mix with dashed naming schemas.

White spaces

Empty end-tags

Implementation with 1 space before closing empty end-tags

example:

<xs:restriction base="xs:ID" />

Indents

Implementation with 2 spaces

example:

1 <xs:element name="railml">
2   <xs:complexType>
3     <xs:sequence>
4       <xs:element name="metadata" type="dc:elementContainer" minOccurs="0" />
5       <xs:element ref="rail:infrastructure" minOccurs="0" />

Line Breaks

Each component declaration must be followed by a line break.

example:

1 <xs:attributeGroup name="aPlaces">
2   <xs:attribute name="category" type="rail:tPlaceCategory" use="required" />
3   <xs:attribute name="count" type="rail:tCounter" use="required" />

There is no maximum line length

Outdated.png Part of the article content is outdated since version 2.0. As to avoid confusion, a current example should be used. Please update this article to reflect recent events or newly available information. Possibly, you will find further details on the discussion pageFerri Leberl (Diskussion) 14:10, 29. Jun. 2016 (CEST)

Each component has to be fully declared on one line without line breaks.

example:

<xs:schema xmlns:rail="http://www.railml.org/schemas/2009" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:dc="http://purl.org/dc/elements/1.1/" targetNamespace="http://www.railml.org/schemas/2009"	elementFormDefault="qualified" version="2.0">

XML Default Values

Empty elements and attributes

see also: W3C XML Recommendation "Tags for Empty Elements"

Implementation with shortened syntax instead of extra closing tag

example:

<xs:element ref="rail:infrastructure" minOccurs="0" />

XML Schema Default Values

Optional and required attributes

see also: W3C XML Schema Recommendation "XML Representation of Attribute Declaration Schema Components"

Implementation without use="optional"

example:

<xs:attribute name="description" type="rail:tElementDescription" />

Implementation with use="required"

example:

<xs:attribute name="id" type="rail:tGenericID" use="required" />

Elements with minimum 1 or maximum 1 occurrence

see also: W3C XML Schema Recommendation "XML Representation of Element Declaration Schema Components"

Implementation without minOccurs="1"

example:

<xs:element name="train" type="rail:eTrain" maxOccurs="unbounded" />

Implementation without maxOccurs="1"

example:

<xs:element ref="rail:timetable" minOccurs="0" />

Occurence restrictions into elements

If possible, all occurence restrictions have to go into element definitions.

xs:sequence should stand without the attributes minOccurs and/or maxOccurs.

example:

1 <xs:extension base="rail:tElementWithIDAndName">
2   <xs:sequence>
3     <xs:element name="metadata" type="dc:elementContainer" minOccurs="0" />
4   </xs:sequence>

Pathes inside XML documents

Attribute xsi:schemaLocation

see also: W3C XML Schema Recommendation "How schema definitions are located on the Web"

Implementation with slashes, no backslashes permitted

example:

<railml xmlns="http://www.railml.org/schemas/2009" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.railml.org/schemas/2009 ../schema/railML.xsd">