Serd 0.20.0
Data Structures | Typedefs | Enumerations

Detailed Description

A lightweight RDF syntax library.

Data Structures

struct SerdNode
struct SerdChunk
struct SerdError
struct SerdURI


typedef struct SerdEnvImplSerdEnv
typedef struct SerdReaderImplSerdReader
typedef struct SerdWriterImplSerdWriter
typedef uint32_tSerdStatementFlags
typedef uint32_tSerdNodeFlags


enum SerdStatus {
enum SerdSyntax { SERD_TURTLE = 1, SERD_NTRIPLES = 2 }
enum SerdStatementFlag {
SERD_EMPTY_S = 1 << 1, SERD_EMPTY_O = 1 << 2, SERD_ANON_S_BEGIN = 1 << 3, SERD_ANON_O_BEGIN = 1 << 4,
SERD_ANON_CONT = 1 << 5, SERD_LIST_S_BEGIN = 1 << 6, SERD_LIST_O_BEGIN = 1 << 7, SERD_LIST_CONT = 1 << 8
enum SerdType {
enum SerdNodeFlag { SERD_HAS_NEWLINE = 1, SERD_HAS_QUOTE = 1 << 1 }
enum SerdStyle {

String Utilities

const uint8_t *serd_strerror (SerdStatus status)
size_tserd_strlen (const uint8_t *str, size_t *n_bytes, SerdNodeFlags *flags)
doubleserd_strtod (const char *str, char **endptr)
void *serd_base64_decode (const uint8_t *str, size_t len, size_t *size)


typedef size_t(*SerdSink )(const void *buf, size_t len, void *stream)
static const SerdURISERD_URI_NULL = {{0,0},{0,0},{0,0},{0,0},{0,0},{0,0}}
const uint8_t *serd_uri_to_path (const uint8_t *uri)
uint8_t *serd_file_uri_parse (const uint8_t *uri, uint8_t **hostname)
boolserd_uri_string_has_scheme (const uint8_t *utf8)
SerdStatusserd_uri_parse (const uint8_t *utf8, SerdURI *out)
voidserd_uri_resolve (const SerdURI *uri, const SerdURI *base, SerdURI *out)
size_tserd_uri_serialise (const SerdURI *uri, SerdSink sink, void *stream)
size_tserd_uri_serialise_relative (const SerdURI *uri, const SerdURI *base, const SerdURI *root, SerdSink sink, void *stream)


static const SerdNodeSERD_NODE_NULL = { 0, 0, 0, 0, SERD_NOTHING }
SerdNodeserd_node_from_string (SerdType type, const uint8_t *str)
SerdNodeserd_node_copy (const SerdNode *node)
boolserd_node_equals (const SerdNode *a, const SerdNode *b)
SerdNodeserd_node_new_uri_from_node (const SerdNode *uri_node, const SerdURI *base, SerdURI *out)
SerdNodeserd_node_new_uri_from_string (const uint8_t *str, const SerdURI *base, SerdURI *out)
SerdNodeserd_node_new_file_uri (const uint8_t *path, const uint8_t *hostname, SerdURI *out, bool escape)
SerdNodeserd_node_new_uri (const SerdURI *uri, const SerdURI *base, SerdURI *out)
SerdNodeserd_node_new_decimal (double d, unsigned frac_digits)
SerdNodeserd_node_new_integer (int64_t i)
SerdNodeserd_node_new_blob (const void *buf, size_t size, bool wrap_lines)
voidserd_node_free (SerdNode *node)

Event Handlers

typedef SerdStatus(*SerdErrorSink )(void *handle, const SerdError *error)
typedef SerdStatus(*SerdBaseSink )(void *handle, const SerdNode *uri)
typedef SerdStatus(*SerdPrefixSink )(void *handle, const SerdNode *name, const SerdNode *uri)
typedef SerdStatus(*SerdStatementSink )(void *handle, SerdStatementFlags flags, const SerdNode *graph, const SerdNode *subject, const SerdNode *predicate, const SerdNode *object, const SerdNode *object_datatype, const SerdNode *object_lang)
typedef SerdStatus(*SerdEndSink )(void *handle, const SerdNode *node)


SerdEnv *serd_env_new (const SerdNode *base_uri)
voidserd_env_free (SerdEnv *env)
const SerdNode *serd_env_get_base_uri (const SerdEnv *env, SerdURI *out)
SerdStatusserd_env_set_base_uri (SerdEnv *env, const SerdNode *uri)
SerdStatusserd_env_set_prefix (SerdEnv *env, const SerdNode *name, const SerdNode *uri)
SerdStatusserd_env_set_prefix_from_strings (SerdEnv *env, const uint8_t *name, const uint8_t *uri)
boolserd_env_qualify (const SerdEnv *env, const SerdNode *uri, SerdNode *prefix, SerdChunk *suffix)
SerdStatusserd_env_expand (const SerdEnv *env, const SerdNode *curie, SerdChunk *uri_prefix, SerdChunk *uri_suffix)
SerdNodeserd_env_expand_node (const SerdEnv *env, const SerdNode *node)
voidserd_env_foreach (const SerdEnv *env, SerdPrefixSink func, void *handle)


SerdReader *serd_reader_new (SerdSyntax syntax, void *handle, void(*free_handle)(void *), SerdBaseSink base_sink, SerdPrefixSink prefix_sink, SerdStatementSink statement_sink, SerdEndSink end_sink)
voidserd_reader_set_error_sink (SerdReader *reader, SerdErrorSink error_sink, void *handle)
void *serd_reader_get_handle (const SerdReader *reader)
voidserd_reader_add_blank_prefix (SerdReader *reader, const uint8_t *prefix)
voidserd_reader_set_default_graph (SerdReader *reader, const SerdNode *graph)
SerdStatusserd_reader_read_file (SerdReader *reader, const uint8_t *uri)
SerdStatusserd_reader_start_stream (SerdReader *me, FILE *file, const uint8_t *name, bool bulk)
SerdStatusserd_reader_read_chunk (SerdReader *me)
SerdStatusserd_reader_end_stream (SerdReader *me)
SerdStatusserd_reader_read_file_handle (SerdReader *reader, FILE *file, const uint8_t *name)
SerdStatusserd_reader_read_string (SerdReader *me, const uint8_t *utf8)
voidserd_reader_free (SerdReader *reader)


SerdWriter *serd_writer_new (SerdSyntax syntax, SerdStyle style, SerdEnv *env, const SerdURI *base_uri, SerdSink sink, void *stream)
voidserd_writer_free (SerdWriter *writer)
SerdEnv *serd_writer_get_env (SerdWriter *writer)
size_tserd_file_sink (const void *buf, size_t len, void *stream)
size_tserd_chunk_sink (const void *buf, size_t len, void *stream)
uint8_t *serd_chunk_sink_finish (SerdChunk *stream)
voidserd_writer_set_error_sink (SerdWriter *writer, SerdErrorSink error_sink, void *handle)
voidserd_writer_chop_blank_prefix (SerdWriter *writer, const uint8_t *prefix)
SerdStatusserd_writer_set_base_uri (SerdWriter *writer, const SerdNode *uri)
SerdStatusserd_writer_set_root_uri (SerdWriter *writer, const SerdNode *uri)
SerdStatusserd_writer_set_prefix (SerdWriter *writer, const SerdNode *name, const SerdNode *uri)
SerdStatusserd_writer_write_statement (SerdWriter *writer, SerdStatementFlags flags, const SerdNode *graph, const SerdNode *subject, const SerdNode *predicate, const SerdNode *object, const SerdNode *object_datatype, const SerdNode *object_lang)
SerdStatusserd_writer_end_anon (SerdWriter *writer, const SerdNode *node)
SerdStatusserd_writer_finish (SerdWriter *writer)

Data Structure Documentation

struct SerdNode

A syntactic RDF node.

Data Fields
const uint8_t * buf Value string.
size_t n_bytes Size in bytes (not including null)
size_t n_chars Length in characters (not including null)
SerdNodeFlags flags Node flags (e.g.

string properties)

SerdType type Node type.
struct SerdChunk

An unterminated string fragment.

Data Fields
const uint8_t * buf Start of chunk.
size_t len Length of chunk in bytes.
struct SerdError

An error description.

Data Fields
SerdStatus status Error code.
const uint8_t * filename File where error was encountered, or NULL.
unsigned line Line where error was encountered, or 0.
unsigned col Column where error was encountered.
const char * fmt Message format string (printf style)
va_list * args Arguments for fmt.
struct SerdURI

A parsed URI.

This struct directly refers to chunks in other strings, it does not own any memory itself. Thus, URIs can be parsed and/or resolved against a base URI in-place without allocating memory.

Data Fields
SerdChunk scheme Scheme.
SerdChunk authority Authority.
SerdChunk path_base Path prefix if relative.
SerdChunk path Path suffix.
SerdChunk query Query.
SerdChunk fragment Fragment.

Typedef Documentation

typedef struct SerdEnvImpl SerdEnv


Represents the state required to resolve a CURIE or relative URI, e.g. the base URI and set of namespace prefixes at a particular point.

typedef struct SerdReaderImpl SerdReader

RDF reader.

Parses RDF by calling user-provided sink functions as input is consumed (much like an XML SAX parser).

typedef struct SerdWriterImpl SerdWriter

RDF writer.

Provides a number of functions to allow writing RDF syntax out to some stream. These functions are deliberately compatible with the sink functions used by SerdReader, so a reader can be directly connected to a writer to re-serialise a document with minimal overhead.

typedef uint32_t SerdStatementFlags

Bitwise OR of SerdNodeFlag values.

typedef uint32_t SerdNodeFlags

Bitwise OR of SerdNodeFlag values.

typedef size_t(* SerdSink)(const void *buf, size_t len, void *stream)

Sink function for raw string output.

typedef SerdStatus(* SerdErrorSink)(void *handle, const SerdError *error)

Sink (callback) for errors.

handleHandle for user data.
errorError description.
typedef SerdStatus(* SerdBaseSink)(void *handle, const SerdNode *uri)

Sink (callback) for base URI changes.

Called whenever the base URI of the serialisation changes.

typedef SerdStatus(* SerdPrefixSink)(void *handle, const SerdNode *name, const SerdNode *uri)

Sink (callback) for namespace definitions.

Called whenever a prefix is defined in the serialisation.

typedef SerdStatus(* SerdStatementSink)(void *handle, SerdStatementFlags flags, const SerdNode *graph, const SerdNode *subject, const SerdNode *predicate, const SerdNode *object, const SerdNode *object_datatype, const SerdNode *object_lang)

Sink (callback) for statements.

Called for every RDF statement in the serialisation.

typedef SerdStatus(* SerdEndSink)(void *handle, const SerdNode *node)

Sink (callback) for anonymous node end markers.

This is called to indicate that the anonymous node with the given value will no longer be referred to by any future statements (i.e. the anonymous serialisation of the node is finished).

Enumeration Type Documentation

enum SerdStatus

Return status code.


No error.


Non-fatal failure.


Unknown error.


Invalid syntax.


Invalid argument.


Not found.


Encountered clashing blank node IDs.


Invalid CURIE (e.g.

prefix does not exist)


Unexpected internal error (should not happen)

enum SerdSyntax

RDF syntax type.


Turtle - Terse RDF Triple Language (UTF-8).

See also

NTriples - Line-based RDF triples (ASCII).

See also

Flags indication inline abbreviation information for a statement.


Empty blank node subject.


Empty blank node object.


Start of anonymous subject.


Start of anonymous object.


Continuation of anonymous node.


Start of list subject.


Start of list object.


Continuation of list.

enum SerdType

Type of a syntactic RDF node.

This is more precise than the type of an abstract RDF node. An abstract node is either a resource, literal, or blank. In syntax there are two ways to refer to a resource (by URI or CURIE) and two ways to refer to a blank (by ID or anonymously). Anonymous (inline) blank nodes are expressed using SerdStatementFlags rather than this type.


The type of a nonexistent node.

This type is useful as a sentinel, but is never emitted by the reader.


Literal value.

A literal optionally has either a language, or a datatype (not both).


URI (absolute or relative).

Value is an unquoted URI string, which is either a relative reference with respect to the current base URI (e.g. "foo/bar"), or an absolute URI (e.g. "").

See also

CURIE, a shortened URI.

Value is an unquoted CURIE string relative to the current environment, e.g. "rdf:type".

See also
CURIE Syntax 1.0

A blank node.

Value is a blank node ID, e.g. "id3", which is meaningful only within this serialisation.

See also
Turtle nodeID

Flags indicating certain string properties relevant to serialisation.


Contains line breaks ('\n' or '\r')


Contains quotes ('"')

enum SerdStyle

Syntax style options.

The style of the writer output can be controlled by ORing together values from this enumeration. Note that some options are only supported for some syntaxes (e.g. NTriples does not support abbreviation and is always ASCII).


Abbreviate triples when possible.


Escape all non-ASCII characters.


Resolve URIs against base URI.


Shorten URIs into CURIEs.


Write output in pages.

Function Documentation

const uint8_t* serd_strerror ( SerdStatus status)

Return a string describing a status code.

size_t serd_strlen ( const uint8_t * str,
size_t * n_bytes,
SerdNodeFlags * flags

Measure a UTF-8 string.

Length of str in characters (except NULL).
strA null-terminated UTF-8 string.
n_bytes(Output) Set to the size of str in bytes (except NULL).
flags(Output) Set to the applicable flags.
double serd_strtod ( const char * str,
char ** endptr

Parse a string to a double.

The API of this function is identical to the standard C strtod function, except this function is locale-independent and always matches the lexical format used in the Turtle grammar (the decimal point is always ".").

void* serd_base64_decode ( const uint8_t * str,
size_t len,
size_t * size

Decode a base64 string.

This function can be used to deserialise a blob node created with serd_node_new_blob().

strBase64 string to decode.
lenThe length of str.
sizeSet to the size of the returned blob in bytes.
A newly allocated blob which must be freed with free().
const uint8_t* serd_uri_to_path ( const uint8_t * uri)

Return the local path for uri, or NULL if uri is not a file URI.

Note this (inappropriately named) function only removes the file scheme if necessary, and returns uri unmodified if it is an absolute path. Percent encoding and other issues are not handled, to properly convert a file URI to a path, use serd_file_uri_parse().

uint8_t* serd_file_uri_parse ( const uint8_t * uri,
uint8_t ** hostname

Get the unescaped path and hostname from a file URI.

uriA file URI.
hostnameIf non-NULL, set to the hostname, if present.
The path component of the URI.

Both the returned path and hostname (if applicable) are owned by the caller and must be freed with free().

bool serd_uri_string_has_scheme ( const uint8_t * utf8)

Return true iff utf8 starts with a valid URI scheme.

SerdStatus serd_uri_parse ( const uint8_t * utf8,
SerdURI * out

Parse utf8, writing result to out.

void serd_uri_resolve ( const SerdURI * uri,
const SerdURI * base,
SerdURI * out

Set out to uri resolved against base.

size_t serd_uri_serialise ( const SerdURI * uri,
SerdSink sink,
void * stream

Serialise uri with a series of calls to sink.

size_t serd_uri_serialise_relative ( const SerdURI * uri,
const SerdURI * base,
const SerdURI * root,
SerdSink sink,
void * stream

Serialise uri relative to base with a series of calls to sink.

The uri is written as a relative URI iff if it a child of base and root. The optional root parameter must be a prefix of base and can be used keep up-references ("../") within a certain namespace.

SerdNode serd_node_from_string ( SerdType type,
const uint8_t * str

Make a (shallow) node from str.

This measures, but does not copy, str. No memory is allocated.

SerdNode serd_node_copy ( const SerdNode * node)

Make a deep copy of node.

a node that the caller must free with serd_node_free().
bool serd_node_equals ( const SerdNode * a,
const SerdNode * b

Return true iff a is equal to b.

SerdNode serd_node_new_uri_from_node ( const SerdNode * uri_node,
const SerdURI * base,
SerdURI * out

Simple wrapper for serd_node_new_uri to resolve a URI node.

SerdNode serd_node_new_uri_from_string ( const uint8_t * str,
const SerdURI * base,
SerdURI * out

Simple wrapper for serd_node_new_uri to resolve a URI string.

SerdNode serd_node_new_file_uri ( const uint8_t * path,
const uint8_t * hostname,
SerdURI * out,
bool escape

Create a new file URI node from a file system path and optional hostname.

Backslashes in Windows paths will be converted and '' will always be percent encoded. If escape is true, all other invalid characters will be percent encoded as well.

If path is relative, hostname is ignored. If out is not NULL, it will be set to the parsed URI.

SerdNode serd_node_new_uri ( const SerdURI * uri,
const SerdURI * base,
SerdURI * out

Create a new node by serialising uri into a new string.

uriThe URI to parse and serialise.
baseBase URI to resolve uri against (or NULL for no resolution).
outSet to the parsing of the new URI (i.e. points only to memory owned by the new returned node).
SerdNode serd_node_new_decimal ( double d,
unsigned frac_digits

Create a new node by serialising d into an xsd:decimal string.

The resulting node will always contain a `.', start with a digit, and end with a digit (i.e. will have a leading and/or trailing `0' if necessary). It will never be in scientific notation. A maximum of frac_digits digits will be written after the decimal point, but trailing zeros will automatically be omitted (except one if d is a round integer).

Note that about 16 and 8 fractional digits are required to precisely represent a double and float, respectively.

dThe value for the new node.
frac_digitsThe maximum number of digits after the decimal place.
SerdNode serd_node_new_integer ( int64_t i)

Create a new node by serialising i into an xsd:integer string.

SerdNode serd_node_new_blob ( const void * buf,
size_t size,
bool wrap_lines

Create a node by serialising buf into an xsd:base64Binary string.

This function can be used to make a serialisable node out of arbitrary binary data, which can be decoded using serd_base64_decode().

bufRaw binary input data.
sizeSize of buf.
wrap_linesWrap lines at 76 characters to conform to RFC 2045.
void serd_node_free ( SerdNode * node)

Free any data owned by node.

Note that if node is itself dynamically allocated (which is not the case for nodes created internally by serd), it will not be freed.

SerdEnv* serd_env_new ( const SerdNode * base_uri)

Create a new environment.

void serd_env_free ( SerdEnv * env)

Free ns.

const SerdNode* serd_env_get_base_uri ( const SerdEnv * env,
SerdURI * out

Get the current base URI.

SerdStatus serd_env_set_base_uri ( SerdEnv * env,
const SerdNode * uri

Set the current base URI.

SerdStatus serd_env_set_prefix ( SerdEnv * env,
const SerdNode * name,
const SerdNode * uri

Set a namespace prefix.

SerdStatus serd_env_set_prefix_from_strings ( SerdEnv * env,
const uint8_t * name,
const uint8_t * uri

Set a namespace prefix.

bool serd_env_qualify ( const SerdEnv * env,
const SerdNode * uri,
SerdNode * prefix,
SerdChunk * suffix

Qualify uri into a CURIE if possible.

SerdStatus serd_env_expand ( const SerdEnv * env,
const SerdNode * curie,
SerdChunk * uri_prefix,
SerdChunk * uri_suffix

Expand curie.

SerdNode serd_env_expand_node ( const SerdEnv * env,
const SerdNode * node

Expand node, which must be a CURIE or URI, to a full URI.

void serd_env_foreach ( const SerdEnv * env,
SerdPrefixSink func,
void * handle

Call func for each prefix defined in env.

SerdReader* serd_reader_new ( SerdSyntax syntax,
void * handle,
void(*)(void *) free_handle,
SerdBaseSink base_sink,
SerdPrefixSink prefix_sink,
SerdStatementSink statement_sink,
SerdEndSink end_sink

Create a new RDF reader.

void serd_reader_set_error_sink ( SerdReader * reader,
SerdErrorSink error_sink,
void * handle

Set a function to be called when errors occur during reading.

The error_sink will be called with handle as its first argument. If no error function is set, errors are printed to stderr in GCC style.

void* serd_reader_get_handle ( const SerdReader * reader)

Return the handle passed to serd_reader_new().

void serd_reader_add_blank_prefix ( SerdReader * reader,
const uint8_t * prefix

Set a prefix to be added to all blank node identifiers.

This is useful when multiple files are to be parsed into the same output (e.g. a store, or other files). Since Serd preserves blank node IDs, this could cause conflicts where two non-equivalent blank nodes are merged, resulting in corrupt data. By setting a unique blank node prefix for each parsed file, this can be avoided, while preserving blank node names.

void serd_reader_set_default_graph ( SerdReader * reader,
const SerdNode * graph

Set the URI of the default graph.

If this is set, the reader will emit quads with the graph set to the given node for any statements that are not in a named graph (which is currently all of them since Serd currently does not support any graph syntaxes).

SerdStatus serd_reader_read_file ( SerdReader * reader,
const uint8_t * uri

Read a file at a given uri.

SerdStatus serd_reader_start_stream ( SerdReader * me,
FILE * file,
const uint8_t * name,
bool bulk

Start an incremental read from a file handle.

Iff bulk is true, file will be read a page at a time. This is more efficient, but uses a page of memory and means that an entire page of input must be ready before any callbacks will fire. To react as soon as input arrives, set bulk to false.

SerdStatus serd_reader_read_chunk ( SerdReader * me)

Read a single "chunk" of data during an incremental read.

This function will read a single top level description, and return. This may be a directive, statement, or several statements; essentially it reads until a '.' is encountered. This is particularly useful for reading directly from a pipe or socket.

SerdStatus serd_reader_end_stream ( SerdReader * me)

Finish an incremental read from a file handle.

SerdStatus serd_reader_read_file_handle ( SerdReader * reader,
FILE * file,
const uint8_t * name

Read file.

SerdStatus serd_reader_read_string ( SerdReader * me,
const uint8_t * utf8

Read utf8.

void serd_reader_free ( SerdReader * reader)

Free reader.

SerdWriter* serd_writer_new ( SerdSyntax syntax,
SerdStyle style,
SerdEnv * env,
const SerdURI * base_uri,
SerdSink sink,
void * stream

Create a new RDF writer.

void serd_writer_free ( SerdWriter * writer)

Free writer.

SerdEnv* serd_writer_get_env ( SerdWriter * writer)

Return the env used by writer.

size_t serd_file_sink ( const void * buf,
size_t len,
void * stream

A convenience sink function for writing to a FILE*.

This function can be used as a SerdSink when writing to a FILE*. The stream parameter must be a FILE* opened for writing.

size_t serd_chunk_sink ( const void * buf,
size_t len,
void * stream

A convenience sink function for writing to a string.

This function can be used as a SerdSink to write to a SerdChunk which is resized as necessary with realloc(). The stream parameter must point to an initialized SerdChunk. When the write is finished, the string should be retrieved with serd_chunk_sink_finish().

uint8_t* serd_chunk_sink_finish ( SerdChunk * stream)

Finish a serialisation to a chunk with serd_chunk_sink().

The returned string is the result of the serialisation, which is NULL terminated (by this function) and owned by the caller.

void serd_writer_set_error_sink ( SerdWriter * writer,
SerdErrorSink error_sink,
void * handle

Set a function to be called when errors occur during writing.

The error_sink will be called with handle as its first argument. If no error function is set, errors are printed to stderr.

void serd_writer_chop_blank_prefix ( SerdWriter * writer,
const uint8_t * prefix

Set a prefix to be removed from matching blank node identifiers.

SerdStatus serd_writer_set_base_uri ( SerdWriter * writer,
const SerdNode * uri

Set the current output base URI (and emit directive if applicable).

Note this function can be safely casted to SerdBaseSink.

SerdStatus serd_writer_set_root_uri ( SerdWriter * writer,
const SerdNode * uri

Set the current root URI.

The root URI should be a prefix of the base URI. The path of the root URI is the highest path any relative up-reference can refer to. For example, with root file:///foo/root and base file:///foo/root/base, file:///foo/root will be written as <../>, but file:///foo will be written non-relatively as file:///foo. If the root is not explicitly set, it defaults to the base URI, so no up-references will be created at all.

SerdStatus serd_writer_set_prefix ( SerdWriter * writer,
const SerdNode * name,
const SerdNode * uri

Set a namespace prefix (and emit directive if applicable).

Note this function can be safely casted to SerdPrefixSink.

SerdStatus serd_writer_write_statement ( SerdWriter * writer,
SerdStatementFlags flags,
const SerdNode * graph,
const SerdNode * subject,
const SerdNode * predicate,
const SerdNode * object,
const SerdNode * object_datatype,
const SerdNode * object_lang

Write a statement.

Note this function can be safely casted to SerdStatementSink.

SerdStatus serd_writer_end_anon ( SerdWriter * writer,
const SerdNode * node

Mark the end of an anonymous node's description.

Note this function can be safely casted to SerdEndSink.

SerdStatus serd_writer_finish ( SerdWriter * writer)

Finish a write.

Variable Documentation

const SerdURI SERD_URI_NULL = {{0,0},{0,0},{0,0},{0,0},{0,0},{0,0}}
const SerdNode SERD_NODE_NULL = { 0, 0, 0, 0, SERD_NOTHING }