DEFINE TABLE website SCHEMAFULL;
    DEFINE FIELD accessed_at ON TABLE website TYPE datetime DEFAULT time::now();
    DEFINE FIELD crawled     ON TABLE website TYPE bool DEFAULT false;
    DEFINE FIELD url         ON TABLE website TYPE string;
    DEFINE FIELD domain      ON TABLE website VALUE parse::url::domain($this.url) ASSERT !type::is::none($value);
    DEFINE FIELD path        ON TABLE website VALUE parse::url::path($this.url) ASSERT !type::is::none($value);

DEFINE TABLE links_to SCHEMAFULL TYPE RELATION FROM website TO website;
    DEFINE FIELD discovered_at ON TABLE links_to TYPE datetime DEFAULT time::now();