Release v5.8.0

A graph can now be read from the model alone: a query follows a typed path over the graph's declared nodes and edges and returns an ordinary read model, and graph specifications can assert values taken from the event time.

Added

• Queries that read a graph, query <Name> => <ReadModel>[] graph <Graph>, with match and optional match path patterns, where equality joined with and, and a return block; both compilers check labels, edge types and direction, aliases, argument and return types, and optional-match returns with PLAY0878 to PLAY0885 (#1169).
• then query in graph specifications, evaluated by the reference graph runner over its in-memory graph, including optional match.
• given clock "<instant>" in graph specifications, which sets $eventContext.occurred for the events the specification appends, with a fixed instant when it is absent (#1171).
• ESM v40 carries graphQueries and the graph specification clock; a model that uses neither keeps its version and bytes.
• A conformance document for graph queries, a section on reading a graph in the graphs documentation, and decision 0139.

Changed

• Variable-length paths, or, ranges, functions and aggregates are refused in a graph query with PLAY0885, and foreach over an event collection follows separately (#1170).