Projection

Projection reduces ledger to rows with distinct attribute values while aggregating their values.

Structure

{
    "_schema": "Projection_1.0",
    "columns": ["EventId"]
}

Parameters

Parameter Name	Required	Type	Description
columns	Yes	string list	List of column names

Behaviour

Records cannot be reduced by Trial, Time, Type of Value column. Records with different Trial, Time or Type are always distinct and cannot be combined using projection, and Value is storing accumulated value of merged records with identical attributes.

Output records will be reduced by the attributes that are listed in the columns list. Those attributes should exists in the loaded data.

_NodePath is a special column name that can be used in the columns list. It stores path of the record through the graph, therefore different records may have a different path. If _NodePath is not listed in the columns list (default behavior) then the records path is ignored during projection and records generated by the projection have a new node path, indicating origination at the projection. If _NodePath is listed in the columns list, then records with different paths are not combined and output records preserve original paths + label of the projection.