数据库UML图关系

Question

我想知道为什么有色关系类型不同...... 据我所知，从我的数据库结构中，我可以从codificators_document_type和document表中得到零或多个值，这个编码器是强制性的。

同样应该是codificator_document_source_type，但我无法弄清楚为什么关系类型不同。 ：（

CREATE TABLE document
(
  source_id integer NOT NULL,
  ....
  type_id character varying(2) NOT NULL,
  register_type_id character varying(1),
  source_type_id character varying(20) NOT NULL,
  CONSTRAINT document_pkey PRIMARY KEY (id),
  CONSTRAINT document_register_type_fkey FOREIGN KEY (register_type_id)
      REFERENCES codificator_document_register_type (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT document_source_type_fkey FOREIGN KEY (source_type_id)
      REFERENCES codificator_document_source_type (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT document_type_fkey FOREIGN KEY (type_id)
      REFERENCES codificator_document_type (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION

CREATE TABLE codificator_document_register_type
(
  id character varying(1) NOT NULL,
  value character varying(255) NOT NULL,
  CONSTRAINT codificator_document_register_pkey PRIMARY KEY (id)
)

CREATE TABLE codificator_document_source_type
(
  id character varying(10) NOT NULL,
  value character varying(255) NOT NULL,
  CONSTRAINT document_source_type_pkey PRIMARY KEY (id)
)

CREATE TABLE codificator_document_type
(
  id character varying(10) NOT NULL,
  value character varying(255) NOT NULL,
  CONSTRAINT codificator_document_type_pkey PRIMARY KEY (id)
)