Subweb and topic names - conflicts, view URLs, and links 
If your TWiki installation has the hierarchical webs feature turned on,
you face subtle issues about subweb (web inside a web) and topic names.
If you are unfamiliar with subwebs, please read 
ManagingWebs#Hierarchical_Webs.
TWiki 5.1.2 has introduced measures to take care of those issues.
As such, in this topic "in the past" means 5.1.1 and earler; "now" means 5.1.2 and later.
 Avoiding conflicts of subweb and topic names 
If the topic 
AaAa.BbB exists, the subweb 
AaAa/BbBb must not exist.
If they co-exist, when the topic AaAa.BbBb is moved, all topics of the 
AaAa/BbBb subweb lose all attachments.
This is because 
AaAa.BbBb topic's attachments are stored in the directory
.../pub/AaAa/BbBb/ while 
AaAa/BbBb subweb's topics have their attachments in the directory 
.../pub/AaAa/BbBb/TOPIC/.
When 
AaAa.BbBb topic is renamed to 
AaAa.CcCc, 
.../pub/AaAa/BbBb directory is renamed to 
.../pub/AaAa/CcCc, which causes 
AaAa/BbBb subweb to lose its all attachments.
In the past there was no mechanism to avoid clash of subweb and topic names.
But now you cannot create a subweb whose name clashes with an existing topic name and vice versa.
Renaming of topics and webs have name clash detection and avoidance logics.
 View URLs 
Let's say there is a subweb named 
AaAa/DdDd.
In the past http://twiki.example.com/cgi-bin/view/AaAa/DdDd led to the "This topic does not exist" page.
But now it causes redirecttion to http://twiki.example.com/cgi-bin/view/AaAa/DdDd/WebHome.
Even now, 
AaAa.BbBb topic and 
AaAa/BbBb subweb may co-exist as a legcy from an old version.
In that case, http://twiki.example.com/cgi-bin/view/AaAa/BbBb shows AaAa.BbBb topic while http://twiki.example.com/cgi-bin/view/AaAa/BbBb/ shows the home page of the 
AaAa/BbBb subweb.
 Links on topics 
TopicName, 
WebName.TopicName, 
[[TopicName][...]], and 
[[WebName.TopicName][...]] become links to the specified topics.
If 
TopicName is actually a subweb name rather than a topic name, those links point to 
WebHome of the subweb.
This may sound strange to a long term TWiki user.
If a subweb 
AaAa/DdDd exists, on the topic 
AaAa.EeEe, 
DdDd and 
[[DdDd]] become links to 
AaAa/DdDd.WebHome.
You can link to a subweb in a relative manner.
The old behavior was to make a link to create the "missing topic" 
AaAa.DdDd.
This is wrong for sure.
And they have to become links - otherwise the label in 
[[link][label]] goes nowhere.
If so, there is no other link destination than 
WebHome of the subweb.
Related Topics: AdminDocumentationCategory