diff --git a/model/ddl.sql b/model/ddl.sql
index 9f15d26..5ac240d 100644
--- a/model/ddl.sql
+++ b/model/ddl.sql
@@ -94,7 +94,7 @@ CREATE TABLE PUBLIC.COMPONENT (
     IN_SERVICE BOOLEAN NOT NULL DEFAULT FALSE,
     STATE INTEGER NOT NULL DEFAULT -1,
     STATUS INTEGER NOT NULL DEFAULT -1,
-    CONNECTION JSONB NOT NULL DEFAULT '{}',
+    CONNECTION JSONB NOT NULL DEFAULT '{}',         -- http://server.baseware.net:6875/books/product-design-docs/page/editor
     LABEL JSONB NOT NULL DEFAULT '{}',
     CONTEXT JSONB NOT NULL DEFAULT '{}',
     OP INTEGER NOT NULL DEFAULT -1,
@@ -145,9 +145,9 @@ CREATE TABLE PUBLIC.MEASUREMENT (
     ID BIGSERIAL PRIMARY KEY,
     TAG VARCHAR(64) NOT NULL DEFAULT '',
     NAME VARCHAR(64) NOT NULL DEFAULT '',
-    TYPE SMALLINT NOT NULL DEFAULT -1,
+    TYPE SMALLINT NOT NULL DEFAULT -1,       -- 要按电力元素的类型（包含可能的结构体类型）来展开
     SIZE INTEGER NOT NULL DEFAULT -1,
-    DATA_SOURCE JSONB NOT NULL DEFAULT '{}', -- {"type":1,"main_pos":"","sub_pos":""}
+    DATA_SOURCE JSONB NOT NULL DEFAULT '{}', -- http://server.baseware.net:6875/books/product-design-docs/page/7eacb
     BAY_UUID UUID NOT NULL,
     COMPONENT_UUID UUID NOT NULL,
     OP INTEGER NOT NULL DEFAULT -1,