> For the complete documentation index, see [llms.txt](https://docs.internetobject.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.internetobject.org/appendices/grammar.md). # Formal Grammar (EBNF) The grammar of Internet Object in EBNF. This appendix gives the grammar of Internet Object in EBNF. It is the normative reference for document structure; the prose chapters explain semantics. Lexical rules (whitespace, comments, literals) are listed at the end. > Notation: `=` defines a rule, `|` alternation, `[ ]` optional, `{ }` zero-or-more, `( )` grouping, `"…"` a literal. Whitespace and comments may appear between tokens unless a rule states otherwise. ## Document ```ebnf document = [ header "---" ] section { sectionBreak section } | value ; (* a bare, header-less value/object *) header = { definition } ; section = [ sectionTag ] ( collection | object ) ; sectionBreak = "---" [ sectionTag ] ; sectionTag = sectionName [ ":" schemaRef ] (* e.g. employee : $employee *) | schemaRef ; (* e.g. $employee *) ``` ## Header definitions ```ebnf definition = "~" key ":" defValue ; key = metaKey | variableKey | refKey ; metaKey = name ; (* metadata *) variableKey = "@" name ; (* value variable *) refKey = "$" name ; (* schema/type reference *) defValue = value | schema ; schemaRef = "$" name ; ``` ## Collections and records ```ebnf collection = record { record } ; record = "~" [ recordBody ] ; (* "~" alone = empty object {} *) recordBody = object | openObject | value ; (* a bare value is promoted to an object *) ``` ## Objects and arrays ```ebnf object = "{" [ memberList ] "}" ; openObject = memberList ; (* unbraced, top-level only *) memberList = member { "," member } [ "," ] ; member = [ key ":" ] [ value ] ; (* keyed or positional; value may be absent *) array = "[" [ valueList ] "]" ; valueList = value { "," value } ; ``` > **A member's value may be absent**, which is how an **empty position** is written: `{p, , q}` holds three members, the middle one carrying no value. A writer is [required to emit this form](/serialization/document-output.md#absent-members-hold-their-place) when a positional member is skipped, so a grammar that demanded a value here would reject conformant writer output. > > An array has no such production: `valueList` requires a value between commas, so `[a,,c]` is **not** an array with a hole — it is an error (`unexpected-token`). Objects bind members by position and therefore need to express a gap; arrays do not. > > The optional trailing comma in `memberList` closes the list; it does **not** add an empty final position. `{a, b,}` holds **two** members, not three. ## Values ```ebnf value = object | array | scalar | variableRef ; variableRef = "@" name | "$" name ; scalar = string | number | specialNumber | bigint | decimal | datetime | binary | boolean | null ; ``` ## Schema (MemberDef and SchemaDef) ```ebnf schema = schemaDef | memberDef | refKey ; schemaDef = "{" memberDefList "}" | memberDefList ; (* object shape *) memberDefList = schemaMember { "," schemaMember } [ "," "*" [ ":" memberDef ] ] ; (* the wildcard `*` is BARE; a quoted "*" is an ordinary memberName *) schemaMember = memberName [ ":" ( type | memberDef | array | schemaRef ) ] ; memberName = name [ "?" ] [ "*" ] (* suffixes belong to the bare-name token *) | regularString | rawString ; (* quoted: literal, no suffixes -- use optional: / "null": in the memberDef *) memberDef = "{" type { "," option } "}" ; (* type + constraints *) option = positionalValue | ( name ":" value ) ; (* e.g. min: 0 *) type = "string" | "int" | "uint8" | "bool" | "datetime" | "decimal" | … ; ``` ## Lexical ```ebnf string = openString | regularString | rawString ; regularString = '"' { char | escape } '"' | "'" { char | escape } "'" ; rawString = "r" ( '"' { rawChar } '"' | "'" { rawChar } "'" ) ; openString = unquotedChar { unquotedChar } ; (* ends at a structural char *) number = [ sign ] ( decInt [ frac ] [ exp ] (* frac/exp: base-10 only *) | frac [ exp ] (* leading-dot form, e.g. .5 *) | hex | octal | binaryNum ) ; hex = ( "0x" | "0X" ) hexDigit { hexDigit } ; octal = ( "0o" | "0O" ) octDigit { octDigit } ; binaryNum = ( "0b" | "0B" ) ( "0" | "1" ) { "0" | "1" } ; bigint = [ sign ] ( decInt | hex | octal | binaryNum ) "n" ; decimal = [ sign ] ( decInt [ frac ] | frac ) "m" ; datetime = "dt" quoted | "d" quoted | "t" quoted ; (* ISO-8601 inside quotes *) binary = "b" quoted ; (* base64 inside quotes *) boolean = "T" | "F" | "true" | "false" ; null = "N" | "null" ; specialNumber = "NaN" | "Inf" | "+Inf" | "-Inf" ; (* reachable via `scalar` *) comment = "#" { anyCharExceptNewline } ; ws = ? Unicode whitespace ? ; name = nameStart { nameChar } ; sectionName = sectionChar { sectionChar } ; (* ANCHORED: the whole name must match *) sectionChar = letter | mark | digit | "-" | "_" ; ``` > `sectionName` is narrower than `name`, and it is the one name in the format with **no quoted form** — the separator line runs to the end of the line, so nothing bounds the name. The rule is anchored on purpose: a parser must not match a prefix and leave the remainder to fail later, or `--- a,b: $x` would silently become a section named `a`. See [Data Sections](/structure-and-syntax/introduction/data.md#section-names-are-bare-names). > This grammar is a working draft for the 1.0 specification. Edge cases (precise open-string termination, escape sequences, and datetime sub-formats) are described in their respective chapters and will be folded in as the grammar is finalized. ## See Also * [Structural Elements](/structure-and-syntax/structural-elements.md) * [Value Representations](/structure-and-syntax/values.md) * [Internet Object Schema](/schema-definition-language/internet-object-schema.md) --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. 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