Re: Navigation question

dawn wrote:
> In another thread "navigation" is again mentioned as undesirable.

Navigation is from here to there.
Things like distance, direction, movement, traveling time, location, path and space are relevant concepts.

In RM the database (at the logical level(*)) is a single-point thing. No navigational term has any meaning in a single point. Conversely, non of the RM terms have any navigational meaning.

(*) Some may maintain that the RM covers no other level.

     A lower, physical level is implied, and AFAIK most
     book that cover RM also touch it. A lot of
     navigation is going on at that level. Without further
     qualification, every navigational remark is, by default
     about that level, the physical level.

Nothing good, nothing bad here, just: navigation is something that does not exist within the RM. 'From a fk in a child to a parent tuple' is at best metaphor (and btw. borrows hierarchical terms).

Now why do people (seem to) want to discuss RM at the exclusion of anything else? I don't know. I know I don't.

You want to discuss navigation? Ok. The RM will not proliferate vocabulary. Furthermore, the first thing people will associate it with is the physical level hidden by the DBMS. You have clearly stated that that is not what you want to talk about.

Let's go navigating the database - not at the physical level, but somewhere else; 'Navigating foreign keys', example:

Let's have a db browser like this:

In the top-bar you can select any table (say A) from the schema, directly below it you can see all data in A in a spreadsheet display.

In the second bar you can select any table (say B) having a foreign key referencing A. Directly below it etc...

Now expand it (release 2) to a network browser, where it is possible have a place for selecting data from all tables C referenced by the foreign keys in B.

This is something one could describe in navigational terms, loosely borrowing RM terms.
Navigation here is the metaphor serving as a guideline for the user interface.

Release 3 would add the extra luxury feature of not just having foreign keys as paths between tables, but any join. Received on Wed Feb 21 2007 - 09:01:04 CET