Changes between Version 3 and Version 4 of S3/S3Model/ComponentResources

Timestamp:

11/24/11 10:36:48 (14 years ago)

Author:

Dominic König

Comment:

--

S3/S3Model/ComponentResources

@@ -7 +7 @@
 [[Image(ComponentTypes.png)]]
 
+== Link-Table Components ==
+
+Components can be bound to their master records via link-tables. In such cases, the foreign key constraints for the component link are all in a separate link-table, whereas both the master table and the component table are completely independent:
+
+{{{
+  master (primary key) <==== (foreign key) link table (foreign key) ====> (primary key) component
+}}}
+
+Link-table component links have some advantages over simple foreign key constraints:
+
+  - they can carry attributes of their own (qualified link)
+  - they provide the option to bind the same component record to multiple master records (many-to-many)
+  - there are several different ways to actuate such links
+
+However, they do have disadvantages too:
+
+  - overhead to maintain a separate database table (processing time, migration issues etc.)
+  - increased complexity to access and query resources (3 tables instead of 2)
+  - increased complexity to handle such links in CRUD and XML/XSLT
+
+=== Link Actuation Methods ===
+
+With link-table component links, you have several different methods available to "actuate" the link. That is, RESTful methods can operate either on the link table, on the component table or both - depending on the request method and the link configuration. The basic "actuation" methods are:
+
+  - ''replace'': hides the link table and always operates on the component table
+  - ''hide'': hides the component table and always operates on the link table
+  - ''link'': operates on the component table for single-record requests, and on the link table for summary requests (=without record ID) and delete
+  - ''embed'': operates on the link table, embeds the component record in single-record requests
+
+The following table gives an overview over link actuation in S3CRUD:
+
+||=Link Actuation Method=||='''replace'''=||='''hide'''=||='''link'''=||='''embed'''=||
+||=CRUD Method=||= =||= =||= =||= =||
+||='''create'''=|| create-form for component || create-form for link || create-form for link || create-form for link with component embedded ||
+||='''read'''=|| read view of component || read view of link || read-view of component || read-view of link (with component embedded^2^) ||
+||='''update'''=|| update-form for component || update-form for link || update-form for component || update-form for link with component embedded ||
+||='''delete'''=|| deletes both, component and link || deletes the link|| deletes the link^1^ || deletes the link^1^ ||
+||='''list'''=|| list view of component || list view of link || list view of link ||  list view of link (with component embedded^2^) ||
+
+  * ^1^ = deletes the component together with the last link if ''autodelete'' option is set
+  * ^2^ = not implemented yet
+
+Other RESTful methods such as S3Search or S3Cube may have their own definitions.
+
+=== Declaration ===
+
+The basic syntax of a link-table component link declaration is:
+
+{{{
+s3mgr.model.add_component("my_component",               # Tablename of the component
+                          my_master=dict(               # Tablename of the master table
+                              link="my_linktable",      # Tablename of the link table
+                              joinby="fieldname",       # FK of the master table (=left key constraint)
+                              key="fieldname",          # FK of the component table (=right key constraint)
+                              actuate="replace",        # Actuation method (see above, optional, defaults to "link")
+                              autodelete=False          # Delete the component record together with the last link (optional, default is False)
+                              widget=Widget,            # Widget to use for embedding (optional, defaults to S3EmbedComponentWidget)
+                              autocomplete="fieldname", # Field in the component to use for autocomplete when embedding the component
+                          ))
+                              
+}}}
+
+If no field is defined for ''autocomplete'', then no autocomplete-widget will be used, but a standard SELECT of options for ''key'' (default behavior).
+
+Important: if you specify a widget for embedding (e.g. S3AddPersonWidget), then you must not use this widget or a widget validator for the right key constraint!
+
 ----