diff --git a/model/ddl.sql b/model/ddl.sql
index 9e13b52..15e644f 100644
--- a/model/ddl.sql
+++ b/model/ddl.sql
@@ -139,9 +139,9 @@ 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,