Arcgis,有点矛盾...

这么一句话:
    1,"图层中并不存储实际的空间数据,而是存储了这些数据源在磁盘上的位置."还有 "地图中显示的数据并没有和地图文件存储在一起,地图中的数据只是引用GIS数据库中的数据源"
    2,当将ArcCatalog中的图层添加到ArcMap中的正在工作的图层上时.
(注这话)"图层被添加到地图上之后,任何对磁盘上原图层的编辑都不会反映到这幅地图上".
我觉得这两句话矛盾了,
既然图层中显示的是数据库中的路径,而数据库中的路径又是存储于磁盘上的,也就是说,源数据是在磁盘上的,为什么"2"又成立呢?

我想到新的想法了,大家帮我看对不对:<div><span style="color: rgb(51, 51, 51); font-family: Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif; font-size: 13px; background-color: rgb(250, 250, 250);">Today,I suddenly have another opinion,that the data source do save in the DataBase,not on the disk.The reason why I confuse about my previous opinion is that, The actually Src is saved on the disk rather than in the database,not like Web,the database just hold the path of the picture,for the pictures are that big. so,now I hold another opinion...so the sentence "once the layer was added to the map,however you change the data on the disk,the there won't be any reflection to the map" is right...</span><br style="color: rgb(51, 51, 51); font-family: Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif; font-size: 13px; background-color: rgb(250, 250, 250);"/><span style="color: rgb(51, 51, 51); font-family: Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif; font-size: 13px; background-color: rgb(250, 250, 250);">can anybody tell me am I right?</span></div><div><span style="color: rgb(51, 51, 51); font-family: Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif; font-size: 13px; background-color: rgb(250, 250, 250);"><br/></span></div>

<p>地图文档只保留数据源路径和符号样式等信息</p><p>但是图层是保留了图形的空间信息的</p>