Changes between Version 5 and Version 6 of S3/S3Model/SuperEntities

Timestamp:

11/01/10 23:40:30 (14 years ago)

Author:

Dominic König

Comment:

--

S3/S3Model/SuperEntities

@@ -5 +5 @@
 == Introduction ==
 
-Sometimes it is useful to share the same component among multiple resources. To realize this, S3XRC uses link tables - so-called ''Super-Entities''.
+Sometimes it is useful to share the same component across multiple resources. To achieve this in a generic way, S3XRC uses link tables - so-called ''Super-Entities'':
 
 [[Image(superentity.png)]]
 
-Instead of having several foreign keys for different primary resources, the shared component contains only one foreign key for the link table.
+Instead of having several foreign keys for different primary resources, the shared component contains only one foreign key to the link table, the so-called ''super-key''.
 
 The primary resource (=instance table) contains the same ''super-key'' field as the component, thus the forward join of resource-to-component can be established as a natural join, i.e. without accessing the link table.
@@ -15 +15 @@
 For the (seldom needed) backward join component-to-resource, the link table needs to be involved because it contains the table name of the primary resource in the field {{instance_type}}.
 
-Disadvantage of the link table method is that the link table needs to be updated whenever a primary resource record is created, updated or deleted. Thus, it is recommended to not use super-entities for resources where the extra load on write can give a serious performance problem (e.g. messages), or at least to keep the super-entity table lean and free of extra references.
+Disadvantage of the link table method is that the link table needs to be updated whenever a primary resource record is created, updated or deleted - which generates some (minimal) extra load on write, however, it is recommended to not use super-entities for resources where the extra load on write can give a serious performance problem (e.g. messages), or at least to keep the super-entity table lean and free of extra references.
 
   - ''code examples to follow...''