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This page is a quick-reference guide to the symbols used in XDI syntax.

Context Symbol Table

Seven single-character delimiters are used to identify the native XDI context types.


Classes (Attribute, Qualifier, or Concept)


Unreserved identifier for a class (can be used for an entity, attribute, or relation)


Reserved identifier for a class (same as #, but defined by the XDI TC)



Identifier for a natural person


Identifier for a group, organization, trademark, or other non-personal legal entity


Identifier for a thing, i.e., a non-legal entity


Identifier for an ordinal

Other Symbol Table






Literal symbol

Identifies a literal arc

Only used for literal arcs; MUST appear alone


Immutability symbol

Signifies an identifier that MUST not be reassigned to another resource

MUST NOT be used with XDI class identifiers, which are immutable by definition


Relativity symbol

Signifies that these semantics of this identifier are limited to the scope of the parent node

Absolute identifiers identify the same resource regardless of the parent node


Triples separator

Separates subject, predicate, object in XDI statement formats

Also used to signify an XDI predicate in the JSON serialization

Context Function Table

Five bracket pairs are used to identify the function of a context node. The absence of any brackets indicates an entity node. Multiple bracket pairs may be used to identify multiple functions, e.g., [<#email>] is a collection of email attributes.


Authority or Owner of a Graph

( )

Root Node (peer root or inner root)*

< >

Attribute node

[ ]

Collection node

| |

Definition node

{ }

Variable node

* Parentheses are also used after context symbols to signify an IRI namespace, e.g., =(mailto:foo@example.com).


XdiSymbolTable (last edited 2016-02-01 02:29:04 by drummond)