[求助]subtypes是什么东西啊？给个解释吧！

<P>subtypes是什么东西啊？给个解释吧！</P>
<P>还有rowsubtypes ？他们是个什么关系啊 ？</P>

<DIV class=GlossaryTerm><A><FONT style="BACKGROUND-COLOR: #0a246a" color=#ffffff>subtype</FONT></DIV><DIV class=Definition><P>In geodatabases, a subset of features in a feature class or objects in a table that share the same attributes. For example, the streets in a streets feature class could be categorized into three <FONT style="BACKGROUND-COLOR: #0a246a" color=#ffffff>subtypes</FONT>: local streets, collector streets, and arterial streets. Creating <FONT style="BACKGROUND-COLOR: #0a246a" color=#ffffff>subtypes</FONT> can be more efficient than creating many feature classes or tables in a geodatabase. For example, a geodatabase with a dozen feature classes that have <FONT style="BACKGROUND-COLOR: #0a246a" color=#ffffff>subtypes</FONT> will perform better than a geodatabase with a hundred feature classes. <FONT style="BACKGROUND-COLOR: #0a246a" color=#ffffff>Subtypes</FONT> also make editing data faster and more accurate because default attribute values and domains can be set up. For example, a Local Street <FONT style="BACKGROUND-COLOR: #0a246a" color=#ffffff>subtype</FONT> could be created and defined so that whenever this type of street is added to the feature class, its speed limit attribute is automatically set to 35 miles per hour.</P></DIV><DIV class=GlossaryTerm></A></DIV>