Façade-X mapping for XML

Set of Documents

This document is listed in Façade-X Mappings, one of the seven Façade-X specification documents produced by the Data Façades Community Group:

1. Façade-X Overview
2. Façade-X Primer
3. Façade-X Schema vocabulary
4. Façade-X Engine vocabulary
5. Façade-X Data Access in SPARQL
6. Façade-X Concepts and Metamodel Specification
7. Façade-X Mappings
   • Façade-X mapping for CSV
   • Façade-X mapping for JSON
   • Façade-X mapping for XML (this document)

Data source

An XML resource yields exactly one data source. Its triples are placed in the named graph whose IRI is the value of fxe:root.

The document element is represented by the root container, which is typed both fx:Root and with the name of the document element.

The XML declaration, the document type declaration, and any comments and processing instructions outside the document element are not represented.

Names

Element and attribute names are turned into IRIs as follows:

1. A name with a namespace name [XML-NAMES] gives the namespace name followed by the local part. When the namespace name does not end with / or #, a # is inserted between them. For example, the element item in the namespace http://example.org/catalog gives http://example.org/catalog#item, and dc:title, with dc bound to http://purl.org/dc/elements/1.1/, gives http://purl.org/dc/elements/1.1/title.
2. A name without a namespace name is minted from the local part and the value of fxe:namespace, as defined in the common principles. With the default namespace, person gives xyz:person.

As defined in [XML-NAMES], an unprefixed attribute has no namespace name, even when a default namespace is declared: it is minted with fxe:namespace. The prefix xml is bound to http://www.w3.org/XML/1998/namespace, so xml:lang gives http://www.w3.org/XML/1998/namespace#lang.

Elements

Each element is represented by a container typed (rdf:type) with the IRI of the element name.

Each attribute of the element is held by a string slot whose IRI is the IRI of the attribute name. Namespace declarations (xmlns and xmlns:* attributes) are not represented.

The content of the element is held by numbered slots, in document order: the first item in rdf:_1, the second in rdf:_2, and so on. The items are:

• each child element, held as the container that represents it;
• each text node, held as a value (see Values).

A text node is a maximal sequence of character data between two pieces of markup. Character references, entity references and CDATA sections are replaced by the characters they stand for and are part of the surrounding text node.

The following are not represented, and do not use up a slot number:

• text nodes that consist only of whitespace (spaces, tabs, carriage returns and line feeds);
• comments;
• processing instructions.

An element with no attributes and no represented content gives a container that is only typed. <empty/>, <empty></empty> and <empty> </empty> have the same representation.

Values

XML without a schema defines no value types. Following the common principles, every attribute value and text node is a literal of type xsd:string, including values such as 10.50 or true. When fxe:xml.lang-tags is true, values in the scope of xml:lang are language-tagged instead (see Language).

The lexical form of a text node is its character data, with whitespace kept: Text and tail keep their spaces. Line ends are normalised as required by XML 1.0 §2.11.

The lexical form of an attribute value is the value after attribute-value normalisation. A line feed written as the character reference 
 is kept as a line feed.

Language

By default, xml:lang is held by a string slot like any other attribute (see Names) and has no other effect on the representation.

When fxe:xml.lang-tags is true, values are also language-tagged, following the scope of xml:lang defined in XML 1.0 §2.12:

• The language of an element is the value of its xml:lang attribute or, when it has none, the language of its parent element. A document element without xml:lang has no language.
• xml:lang="" gives the element no language.
• A value of xml:lang that is not a well-formed language tag [BCP47] is treated as xml:lang="".
• Each text node of an element that has a language, and each attribute value of that element, is a language-tagged string whose lexical form is as defined in Values and whose language tag is the language of the element, as written in the source.
• Values of attributes in the XML namespace (xml:lang, xml:space, xml:base, xml:id) are not language-tagged.
• The xml:lang slot is kept.

All other values are of type xsd:string.

The language of an element is determined by the XML source alone. Options that omit triples do not change it: with fxe:null-string set to "", the slot for xml:lang="" is omitted, but the element still has no language.