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Schema

A schema is a named, reusable declaration of the wire format used to (de)serialize the input or output of a transform function (for example an ingestion or a projection). Declaring the format as a model element means the linkage between a transform function and its format lives in the model itself, rather than being maintained externally.

1. Declaring a schema​

A schema is a top-level model element introduced with the schema keyword, followed by a name and a serialization format:

schema fixml XML

The format refers to a value of the built-in SerializationFormat enumeration:

FormatMeaning
JSONJSONJSON Text-based, language-independent format with key-value pairs (eg Name: Dave)., following a standard JSONJSON Text-based, language-independent format with key-value pairs (eg Name: Dave). representation of the model.
RUNE_JSONJSONJSON Text-based, language-independent format with key-value pairs (eg Name: Dave)., following the Rune-specific JSONJSON Text-based, language-independent format with key-value pairs (eg Name: Dave). standard.
XMLXMLXML Text-based format used to store and transport data in a structured way that both humans and machines can read., typically configured by an associated XMLXML Text-based format used to store and transport data in a structured way that both humans and machines can read. configuration file that maps the schema onto the Rune type.
CSVComma-separated values. Only valid for tabular types, i.e. types whose attributes are all single-cardinalityCardinality The number of elements in a set or other grouping, as a property of that grouping. basic types.
CSV_LABELLEDComma-separated values with a header row of human-readable labels.

2. Referencing a schema from a transform function​

Transform functions (ingest, projection, enrich) declare the format they read or write through a transform annotation. The annotation can reference either a bare format or a schema:

func Ingest_FpmlConfirmationToTradeState:
    [ingest fixml]
    inputs:
        fpmlDocument Document (0..1)
    output:
        tradeState TradeState (0..1)

Referencing a schema by name ([ingest fixml]) is equivalent to referencing its format ([ingest XML]), but additionally carries the schema's identity, which is what links it to its external configuration (see below). A schema is indexed like any other named model element, so it can be referenced from models that depend on the one declaring it.

3. Annotations on a schema​

A schema can carry annotations.

3.1 [externalConfig]​

The [externalConfig] annotation may only be applied to a schema. It signifies that the schema has an externally-configured serialization configuration — typically the path to an XMLXML Text-based format used to store and transport data in a structured way that both humans and machines can read. configuration file that maps the wire format onto the Rune type. The configuration is supplied outside the model and is looked up by the schema's name.

schema fixml XML
    [externalConfig]

When a referenced schema is marked [externalConfig], its configured config path is included in the code generated for the transform function. When the schema is not marked [externalConfig], no config path is generated, even if one happens to be configured.

Validation keeps the marker and the external configuration in sync:

  • A schema marked [externalConfig] for which no external serialization configuration is configured is an error.
  • An external serialization configuration that is configured for a schema which is not marked [externalConfig] produces a warning, because the configuration would otherwise be silently ignored.

3.2 [deprecated]​

A schema can be marked [deprecated] to signal that it will be removed or replaced. Referencing a deprecated schema produces a deprecation warning, consistent with deprecating other model elements such as types and functions.

schema oldFixml XML
    [deprecated]