# `RDF.TriG.Encoder`
[🔗](https://github.com/rdf-elixir/rdf-ex/blob/v3.0.1/lib/rdf/serializations/trig/encoder.ex#L1)

An encoder for TriG serializations of RDF.ex data structures.

As for all encoders of `RDF.Serialization.Format`s, you normally won't use these
functions directly, but via one of the `write_` functions on the `RDF.TriG`
format module or the generic `RDF.Serialization` module.

## Options

- `:content`: Allows specifying the content and structure of the Turtle document
  to be rendered and defining which parts should be generated in which order.
  This option accepts lists of the values `:base`, `:prefixes`, `:default_graph` and `:named_graphs`.
  You can also use `:directives` to specify `[:base, :prefixes]` and `:graphs`
  to specify `[:default_graph, :named_graphs]` as a group.
  Additionally, arbitrary strings can be included at desired positions to customize
  the document.

      RDF.TriG.write_string(dataset, content: [
        "# === HEADER ===\n\n",
        :directives,
        "\n# === NAMED GRAPHS ===\n\n",
        :named_graphs
        "\n# === DEFAULT GRAPH ===\n\n",
        :default_graph
      ])

- `:prefixes`: Allows to specify the prefixes to be used as a `RDF.PrefixMap` or
  anything from which a `RDF.PrefixMap` can be created with `RDF.PrefixMap.new/1`.
  If not specified the prefixes from all the graphs of the given dataset are used
  or if these are also not present the `RDF.default_prefixes/0`.
- `:base`: : Allows to specify the base URI to be used for a `@base` directive.
  If not specified the `RDF.default_base_iri/0` is used.
- `:directive_style`: Specifies the style of directives to be used in the document.
  Possible values are `:turtle` and `:sparql` (default: `:turtle`).
- `:implicit_base`: This boolean flag allows to use a base URI to get relative IRIs
  without embedding it explicitly in the content with a `@base` directive, so that
  the URIs will be resolved according to the remaining strategy specified in
  section 5.1 of [RFC3986](https://www.ietf.org/rfc/rfc3986.txt) (default: `false`).
- `:base_description`: Allows to provide a description of the resource denoted by
  the base URI. This option is especially useful when the base URI is actually not
  specified, e.g. in the common use case of wanting to describe the document
  itself, which should be denoted by the URL where it is hosted as the implicit base
  URI.
- `:line_prefix`: Allows to specify a function returning prefixes for the encoded lines.
  When this function is defined, the `:single_triple_lines` option is implicitly set, so
  that each line encodes at most one triple.
  The function receives three arguments:
  1. `type` - one of the following values specifying the content of the line: `:triple`,
    `:description`, `:graph` (for named graphs in TriG only), `:closing`
  2. `value` - a `type` specific value for the content in this line
      - for `:triple`: the `RDF.Triple` encoded in this line
      - for `:description`: the subject whose description is started in this line
      - for `:graph`: the name of the graph, opened in this line
      - for `:closing`: a value specifying which element is closed in this line
  3. `graph_name` - the name of graph (in Turtle this is always `nil`)
- `:single_triple_lines`: When set to `true` each line encodes at most one triple, i.e.
   no object lists with multiple objects are used and no Turtle list encodings are used.
   This option is in of itself is not very useful. It is set implicitly when defining
   a `:line_prefix` function which depends on this mode to produce useful results.
- `:indent`: Allows to specify the number of spaces the output should be indented.
- `:indent_width`: Allows to specify the number of spaces that should be used for
  indentations (default: 4).
- `:pn_local_validation`: This option controls how IRIs are validated the check
   whether they can encoded as a prefixed name. Available settings are:
  - `:fast` (default): Provides a quick and efficient validation that covers most
    common cases. It does not handle every possible valid scenario, focusing instead
    on typical structures encountered in prefixed names.
  - `:none`: Disables validation entirely. Use this mode if you are confident that
    all your IRIs are already compliant with prefixed name requirements, allowing you
    to bypass validation checks for increased performance.
  - Note: Currently, a `:strict` mode, which would provide comprehensive validation
    conforming strictly to the Turtle specification, is not implemented.
    Contributions for implementing this mode are welcome.
- `:rdf_star`: Allows to skip a RDF-star related preprocessing step. This can be
   used to improve performance a little bit when you know the encoded data doesn't
   include any RDF-star statements. Defaults to the returned value of `RDF.star?/0`.

---

*Consult [api-reference.md](api-reference.md) for complete listing*