terms.html

<section>
  <h1>General Terminology</h1>
  <p>This document uses the following terms as defined in JSON [[!RFC7159]]. Refer
    to the <em>JSON Grammar</em> section in [[!RFC7159]] for formal definitions.</p>

  <dl class="termlist">
    <dt><dfn data-lt="arrays">array</dfn></dt><dd>
      In the JSON serialization, an array structure is represented as square brackets surrounding zero
      or more values. Values are separated by commas.
      In the <em>abstract representation</em>, an array is an <em>ordered</em> collection of zero or more values.
      While JSON-LD uses the same array representation as JSON,
      the collection is <em>unordered</em> by default. While order is
      preserved in regular JSON arrays, it is not in regular JSON-LD arrays
      unless specifically defined (see
      <cite><a href="http://www.w3.org/TR/json-ld/#sets-and-lists" class="externalDFN">Sets and Lists</a></cite> in
      the JSON-LD specification [[JSON-LD]]).</dd>
    <dt><dfn data-lt="JSON objects">JSON object</dfn></dt><dd>
      In the JSON serialization, an object structure is represented as a pair of curly brackets surrounding zero or
      more key-value pairs. A key is a <a>string</a>. A single colon comes after
      each key, separating the key from the value. A single comma separates a value
      from a following key. In JSON-LD the keys in an object MUST be unique.
      In the <em>abstract representation</em> a <a>JSON object</a> is equivalent to a
      <a href="http://www.w3.org/TR/WebIDL/#dfn-dictionary" class="externalDFN"><dfn data-lt="dictionaries">dictionary</dfn></a> (see [[WebIDL-2]]).</dd>
    <dt><dfn>null</dfn></dt><dd>
      The use of the <a>null</a> value within JSON-LD is used to
      ignore or reset values. A key-value pair in the <code>@context</code> where
      the value, or the <code>@id</code> of the value, is <a>null</a>
      explicitly decouples a term's association with an IRI. A key-value pair in
      the body of a <a>JSON-LD document</a> whose value is <a>null</a> has the
      same meaning as if the key-value pair was not defined. If
      <code>@value</code>, <code>@list</code>, or <code>@set</code> is set to
      <a>null</a> in expanded form, then the entire <a>JSON
      object</a> is ignored.</dd>
    <dt><dfn data-lt="numbers|JSON number|JSON numbers">number</dfn></dt><dd>
      In the JSON serialization, a number is similar to that used in most programming languages, except
      that the octal and hexadecimal formats are not used and that leading
      zeros are not allowed.
      In the <em>abstract representation</em>, a <a>number</a> is equivalent to either
      a <a href="http://www.w3.org/TR/WebIDL/#dfn-long" class="externalDFN">long</a>
      or <a href="http://www.w3.org/TR/WebIDL/#dfn-double" class="externalDFN">double</a>, depending
      on if the number has a non-zero fractional part (see [[WebIDL-2]]).</dd>
    <dt><dfn>scalar</dfn></dt><dd>
      A scalar is either a JSON <a>string</a>, <a>number</a>, <a>true</a>,
      or <a>false</a>.</dd>
    <dt><dfn data-lt="strings">string</dfn></dt><dd>
      A string is a sequence of zero or more Unicode (UTF-8) characters,
      wrapped in double quotes, using backslash escapes (if necessary). A
      character is represented as a single character string.</dd>
    <dt><dfn>true</dfn> and <dfn>false</dfn></dt><dd>
      Values that are used to express one of two possible
      <a href="http://www.w3.org/TR/WebIDL/#idl-boolean" class="externalDFN">boolean</a> states.</dd>
  </dl>

  <p>Furthermore, the following terminology is used throughout this document:</p>

  <dl class="termlist">
    <dt><dfn data-lt="absolute IRIs">absolute IRI</dfn></dt><dd>
      An absolute <a>IRI</a> is defined in [[!RFC3987]] containing a <em>scheme</em> along with a <em>path</em> and
      optional <em>query</em> and fragment segments.</dd>
    <dt><dfn data-lt="base IRIs">base IRI</dfn></dt><dd>
      The <a>base IRI</a> is an <a>absolute IRI</a> established in the <a>context</a>,
      or is based on the <a>JSON-LD document</a> location. The <a>base IRI</a> is used to turn
      <a>relative IRIs</a> into <a>absolute IRIs</a>.</dd>
    <dt><dfn data-lt="blank nodes">blank node</dfn></dt><dd>
      A <a>node</a> in a <a>graph</a> that is neither an
      <a>IRI</a>, nor a <a>JSON-LD value</a>, nor a <a>list</a>.
      A <a>node</a> does not contain a de-referenceable
      identifier because it is either ephemeral in nature or does not contain information that needs to be
      linked to from outside of the linked data graph. A blank node is assigned an identifier starting with
      the prefix <code>_:</code>.</dd>
    <dt><dfn data-lt="blank node identifiers">blank node identifier</dfn></dt><dd>
      A blank node identifier is a string that can be used as an identifier for a
      <a>blank node</a> within the scope of a JSON-LD document. Blank node identifiers
      begin with <code>_:</code>.</dd>
    <dt><dfn data-lt="compact iris">compact IRI</dfn></dt><dd>
      A compact IRI is has the form of <a>prefix</a>:<em>suffix</em> and is used as a way
      of expressing an <a>IRI</a> without needing to define separate <a>term</a> definitions for
      each IRI contained within a common vocabulary identified by <a>prefix</a>.</dd>
    <dt><dfn data-lt="contexts">context</dfn></dt><dd>
      A a set of rules for interpreting a <a>JSON-LD document</a> as specified in
      <cite><a href="http://www.w3.org/TR/json-ld/#the-context">The Context</a></cite> of the [[JSON-LD]] specification.</dd>
    <dt><dfn>datatype IRI</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-datatype-iri" class="externalDFN">datatype IRI</a>
      as specified by [[RDF11-CONCEPTS]].</dd>
    <dt><dfn>default graph</dfn></dt><dd>
      The default graph is the only graph in a JSON-LD document which has no <a>graph name</a>.
      When executing an algorithm, the graph where data should be placed
      if a <a>named graph</a> is not specified.</dd>
    <dt><dfn>default language</dfn></dt><dd>
      The default language is set in the <a>context</a> using the <code>@language</code> key whose
      value MUST be a <a>string</a> representing a [[!BCP47]] language code or <a>null</a>.</dd>
    <dt><dfn>default object</dfn></dt><dd>
      A <a>default object</a> is a <a>JSON object</a> that has a <code>@default</code> member.</dd>
    <dt><dfn data-lt="edges">edge</dfn></dt><dd>
      Every <a>edge</a> has a direction associated with it and is labeled with
      an <a>IRI</a> or a <a>blank node identifier</a>. Within the JSON-LD syntax
      these edge labels are called <a>properties</a>. Whenever possible, an
      <a>edge</a> should be labeled with an <a>IRI</a>.</dd>
    <dt><dfn data-lt="expanded term definitions">expanded term definition</dfn></dt><dd>
      An expanded term definition, is a <a>term definition</a> where the value is a <a>JSON object</a>
      containing one or more <a>keyword</a> <a>properties</a> to define the associated <a>absolute IRI</a>,
      if this is a reverse property, the type associated with string values, and a container mapping.</dd>
    <dt><dfn data-lt="JSON-LD frame|frames">Frame</dfn></dt><dd>
      A <a>JSON-LD document</a>, which describes the form for outputting
      <a>JSON-LD input</a> using matching and embedding rules.</dd>
    <dt><dfn>frame object</dfn></dt><dd>
      A frame object is a a <a>dictionary</a> element withing a <a>frame</a>
      which represents a specific portion of the <a>frame</a> matching either a
      <a>node object</a> or a <a>value object</a> in the input.</dd>
    <dt><dfn data-lt="graph names">graph name</dfn></dt><dd>
      The <a>IRI</a> identifying a <a>named graph</a>.</dd>
    <dt><dfn data-lt="index maps">index map</dfn></dt><dd>
      An <a>index map</a> is a <a>JSON object</a> value of a <a>term</a> defined with
      <code>@container</code> set to <code>@index</code>, whose values MUST be any of the following types:
        <a>string</a>,
        <a>number</a>,
        <a>true</a>,
        <a>false</a>,
        <a>null</a>,
        <a>node object</a>,
        <a>value object</a>,
        <a>list object</a>,
        <a>set object</a>, or
        an <a>array</a> of zero or more of the above possibilities.
      </dd>
    <dt><dfn data-lt="IRIs|Internationalized Resource Identifier"><abbr title="Internationalized Resource Identifier">IRI</abbr></dfn></dt><dd>
      An Internationalized Resource Identifier as described in [[!RFC3987]].</dd>
    <dt><dfn data-lt="JSON-LD documents">JSON-LD document</dfn></dt><dd>
      A <a>JSON-LD document</a> is a serialization of a collection of
      <a>graphs</a> and comprises exactly one
      <a>default graph</a> and zero or more <a>named graphs</a>.</dd>
    <dt><dfn data-lt="JSON-LD values">JSON-LD value</dfn></dt><dd>
      A <a data-lt="JSON-LD values">JSON-LD value</a> is a <a>string</a>, a <a>number</a>,
      <a>true</a> or <a>false</a>, a <a>typed value</a>, or a
      <a>language-tagged string</a>.</dd>
    <dt><dfn data-lt="keywords">keyword</dfn></dt><dd>
      A JSON key that is specific to JSON-LD, specified in the JSON-LD Syntax specification [[!JSON-LD]]
      in the section titled <cite><a href="http://www.w3.org/TR/json-ld/#syntax-tokens-and-keywords">Syntax Tokens and Keywords</a></cite>.</dd>
    <dt><dfn data-lt="language maps">language map</dfn></dt><dd>
      An <a>language map</a> is a <a>JSON object</a> value of a <a>term</a> defined with
      <code>@container</code> set to <code>@language</code>, whose keys MUST be <a>strings</a> representing
      [[!BCP47]] language codes and the values MUST be any of the following types:
        <a>null</a>,
        <a>string</a>, or
        an <a>array</a> of zero or more of the above possibilities.
      </dd>
    <dt><dfn data-lt="language-tagged strings">language-tagged string</dfn></dt><dd>
      A <a>language-tagged string</a> consists of a string and a non-empty language
      tag as defined by [[!BCP47]]. The language tag MUST be well-formed according to
      <a href="http://tools.ietf.org/html/bcp47#section-2.2.9">section 2.2.9 Classes of Conformance</a>
      of [[!BCP47]], and is normalized to lowercase.</dd>
    <dt><dfn>Linked Data</dfn></dt><dd>
      A set of documents, each containing a representation of a <a>linked data graph</a>.</dd>
    <dt><dfn data-lt="graph|graphs">linked data graph</dfn></dt><dd>
      A labeled directed graph, i.e., a set of <a>nodes</a>
      connected by <a>edges</a>,
      as specified in the <cite><a href="http://www.w3.org/TR/json-ld/#data-model">Data Model</a></cite>
      section of the JSON-LD specification [[!JSON-LD]].
      A <a>linked data graph</a> is a generalized representation of a
      <cite><a href="http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-graph">RDF graph</a></cite>
      as defined in [[!RDF-CONCEPTS]].</dd>
    <dt><dfn data-lt="lists">list</dfn></dt><dd>
      A <a>list</a> is an ordered sequence of <a>IRIs</a>,
      <a>blank nodes</a>, and <a>JSON-LD values</a>.</dd>
    <dt><dfn data-lt="list objects">list object</dfn></dt><dd>
      A <a>list object</a> is a <a>JSON object</a> that has an <code>@list</code>
      member.</dd>
    <dt><dfn data-lt="literals">literal</dfn></dt><dd>
      An <a>object</a> expressed as a value such as a string, number or in expanded form.</dd>
    <dt><dfn data-lt="local contexts">local context</dfn></dt><dd>
      A <a>context</a> that is specified within a <a>JSON object</a>,
      specified via the <code>@context</code> <a>keyword</a>.</dd>
    <dt><dfn data-lt="named graphs">named graph</dfn></dt><dd>
      A <a>linked data graph</a> that is identified by an <a>IRI</a> or <a>blank node</a>
    <dt><dfn data-lt="nested properties">nested property</dfn></dt><dd>
      A <a>nested property</a> is a <a>property</a> which is contained within an object referenced by
      a semantically meaningless <em>nesting property</em>.
    </dd>
      (the <a>graph name</a>) and a <a>graph</a>.</dd>
    <dt><dfn data-lt="nodes">node</dfn></dt><dd>
      Every <a>node</a> is an <a>IRI</a>, a <a>blank node</a>,
      a <a>JSON-LD value</a>, or a <a>list</a>.
      A piece of information that is represented in a <a>linked data graph</a>.</dd>
    <dt><dfn data-lt="node objects">node object</dfn></dt><dd>
      A <a>node object</a> represents zero or more <a>properties</a> of a
      <a>node</a> in the <a>graph</a> serialized by the
      <a>JSON-LD document</a>. A <a>JSON object</a> is a <a>node object</a>
      if it exists outside of the JSON-LD <a>context</a> and:
      <ul>
        <li>it does not contain the <code>@value</code>, <code>@list</code>,
          or <code>@set</code> keywords, or</li>
        <li>it is not the top-most <a>JSON object</a> in the JSON-LD document consisting
          of no other members than <code>@graph</code> and <code>@context</code>.</li>
      </ul>
    </dd>
    <dt><dfn data-lt="node references">node reference</dfn></dt><dd>
      A <a>node object</a> used to reference a node having only the
      <code>@id</code> key.</dd>
    <dt><dfn data-lt="objects">object</dfn></dt><dd>
      A <a>node</a> in a <a>linked data graph</a> with at least one incoming edge.</dd>
    <dt><dfn data-lt="prefixes">prefix</dfn></dt><dd>
      A <a>prefix</a> is a <a>term</a> that expands to a vocabulary <a>base IRI</a>. It
      is typically used along with a <em>suffix</em> to form a <a>compact IRI</a> to create an IRI
      within a vocabulary.</dd>
    <dt><dfn data-lt="properties">property</dfn></dt><dd>
      The <a>IRI</a> label of an edge in a <a>linked data graph</a>.</dd>
    <dt><dfn data-lt="quads">quad</dfn></dt><dd>
      A piece of information that contains four items; a <a>subject</a>, a <a>property</a>,
      an <a>object</a>, and a <a>graph name</a>.</dd>
    <dt><dfn>RDF collection</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf-schema/#ch_collectionvocab" class="externalDFN">collection</a>
      as specified by [[RDF-SCHEMA]].</dd>
    <dt><dfn>RDF dataset</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-dataset" class="externalDFN">dataset</a>
      as specified by [[RDF11-CONCEPTS]] representing a collection of
      <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-graph">RDF graphs</a>.</dd>
    <dt><dfn data-lt="RDF literals">RDF literal</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-literal" class="externalDFN">literal</a>
      as specified by [[RDF11-CONCEPTS]].</dd>
    <dt><dfn>RDF object</dfn></dt><dd>
      An <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-object" class="externalDFN">object</a>
      as specified by [[RDF11-CONCEPTS]].</dd>
    <dt><dfn data-lt="predicate|RDF predicates">RDF predicate</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-predicate" class="externalDFN">predicate</a>
      as specified by [[RDF11-CONCEPTS]].</dd>
    <dt><dfn>RDF resource</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-resource" class="externalDFN">resource</a>
      as specified by [[RDF11-CONCEPTS]].</dd>
    <dt><dfn>RDF subject</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-subject" class="externalDFN">subject</a>
      as specified by [[RDF11-CONCEPTS]].</dd>
    <dt><dfn data-lt="triple|triples|RDF triples">RDF triple</dfn></dt><dd>
      A <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple" class="externalDFN">triple</a>
      as specified by [[RDF11-CONCEPTS]].</dd>
    <dt><dfn data-lt="relative IRIs">relative IRI</dfn></dt><dd>
      A relative IRI is an <a>IRI</a> that is relative to some other <a>absolute IRI</a>.</dd>
    <dt><dfn>set object</dfn></dt><dd>
      A <a>set object</a> is a <a>JSON object</a> that has an <code>@set</code>
      member.</dd>
    <dt><dfn data-lt="subjects">subject</dfn></dt><dd>
      A <a>node</a> in a <a>linked data graph</a> with at least one outgoing edge, related to an <a>object</a> node through a <a>property</a>.</dd>
    <dt><dfn data-lt="terms">term</dfn></dt><dd>
      A <a>term</a> is a short word defined in a <a>context</a> that MAY be expanded to an <a>IRI</a>
    </dd>
    <dt><dfn data-lt="term definitions">term definition</dfn></dt><dd>
      A term definition is an entry in a <a>context</a>, where the key defines a <a>term</a> which may be used within
      a <a>JSON object</a> as a <a>property</a>, type, or elsewhere that a string is interpreted as a vocabulary item.
      Its value is either a string, expanding to an absolute IRI, or an <a>expanded term definition</a>.
    </dd>
    <dt><dfn>typed literal</dfn></dt><dd>
      A <a>typed literal</a> is a <a>literal</a> with an associated <a>IRI</a>
      which indicates the literal's datatype. See <cite><a
      href="http://www.w3.org/TR/rdf11-concepts/#dfn-typed-literal">languaged-tagged literal</a></cite> in [[!RDF-CONCEPTS]].</dd>
    <dt><dfn data-lt="typed values">typed value</dfn></dt><dd>
      A <a>typed value</a> consists of a value, which is a <a>string</a>, and a type,
      which is an <a>IRI</a>.</dd>
    <dt><dfn data-lt="value objects">value object</dfn></dt><dd>
      A <a>value object</a> is a <a>JSON object</a> that has an <code>@value</code>
      member.</dd>
    <dt><dfn>vocabulary mapping</dfn></dt><dd>
      The vocabulary mapping is set in the <a>context</a> using the <code>@vocab</code> key whose
      value MUST be an <a>absolute IRI</a> <a>null</a>.</dd>
  </dl>
</section>

<section>
  <h1>Algorithm Terms</h1>

  <p>The Following terms are used within specific algorithms.</p>

  <dl class="termlist">
    <dt><dfn>active context</dfn></dt><dd>
      A <a>context</a> that is used to resolve <a>terms</a> while the processing
      algorithm is running.</dd>
    <dt><dfn>active graph</dfn></dt><dd>
      The name of the currently active graph that the processor should use when
      processing.</dd>
    <dt><dfn>active object</dfn></dt><dd>
      The currently active object that the processor should use when
      processing.</dd>
    <dt><dfn>active property</dfn></dt><dd>
      The currently active <a>property</a> or <a>keyword</a> that the processor
      should use when processing. The <a>active property</a> is represented in
      the original lexical form, which is used for finding coercion mappings in
      the <a>active context</a>.</dd>
    <dt><dfn>active subject</dfn></dt><dd>
      The currently active subject that the processor should use when
      processing.</dd>
    <dt><dfn>explicit inclusion flag</dfn></dt><dd>
      A flag specifying that for <a>properties</a> to be included in the output, they
      must be explicitly declared in the matching <a>frame</a>.</dd>
    <dt><dfn>framing state</dfn></dt><dd>
      A <a>dictionary</a> containing values for the
      <a>object embed flag</a>, the
      <a>require all flag</a>, the
      <a>explicit inclusion flag</a> and the
      <a>omit default flag</a>.</dd>
    <dt><dfn>input frame</dfn></dt><dd>
      The initial <a>Frame</a> provided to the framing algorithm.</dd>
    <dt><dfn>JSON-LD input</dfn></dt><dd>
      The JSON-LD data structure that is provided as input to the algorithm.</dd>
    <dt><dfn>JSON-LD output</dfn></dt><dd>
      The JSON-LD data structure that is produced as output by the algorithm.</dd>
    <dt><dfn data-lt="JSON-LD Processors|Processors">JSON-LD Processor</dfn></dt><dd>
      A <a>JSON-LD Processor</a> is a system which can perform the algorithms defined in [[JSON-LD-API]].</dd>
    <dt><dfn>map of flattened subjects</dfn></dt><dd>
      A map of subjects that is the result of the
      <a href="https://www.w3.org/TR/json-ld-api/#node-map-generation">Node Map Generation algorithm</a>.</dd>
    <dt><dfn>object embed flag</dfn></dt><dd>
      A flag specifying that <a>node objects</a> should be directly embedded in the output,
      instead of being referred to by their <a>IRI</a>.</dd>
    <dt><dfn>omit default flag</dfn></dt><dd>
      A flag specifying that properties that are missing from the
      <a>JSON-LD input</a>, but present in the <a>input frame</a>
      should be omitted from the output.</dd>
    <dt><dfn>processor state</dfn></dt><dd>
      The <a>processor state</a>, which includes the <a>active
      context</a>, <a>active subject</a>, and
      <a>active property</a>. The <a>processor state</a> is managed
      as a stack with elements from the previous <a>processor state</a>
      copied into a new <a>processor state</a> when entering a new
      <a>JSON object</a>.</dd>
    <dt><dfn data-lt="promises">promise</dfn></dt><dd>
      A <em>promise</em> is an object that represents the eventual result of a single asynchronous operation.
      Promises are defined in [[!promises-guide]].</dd>
    <dt><dfn>require all flag</dfn></dt><dd>
      A flag specifying that all properties present in the <a>input frame</a>
      MUST either have a default value or be present in the <a>JSON-LD
      input</a> for the frame to match.</dd>
  </dl>
</section> <!-- end of Algorithm Terms section -->