Semantics

[Henry Story <henry.story@xxxxxxxxxxx>]

Hi,

 Syntax and semantics being very closely related fields I thought I 
could post this here. I hope I am not intruding.

I am currently working on a blog file format for BlogEd, a neat and 
simple client side blog editor. In the process I got interested in the 
semantics behind the Atom file format. I started off with the Atom-Owl 
spec from Danny Ayers, but had to transform it into something like the 
following, in order to be able to represent the evolution of a feed:

Some points of clarification:
	- An Entry points to a number of time stamped EntryStates, which 
allows one to represent the evolution of changes to an Entry. So 
rectifying a spelling mistake in the title of an entry creates a new 
time stamped EntryState, for example.
	- A Feed points to a header Entry and all the other Entries that 
constitute the feed. I did this after noticing a simple one to one 
mapping between Entry, EntryStates and the Atom Feed properties:

        + Feed.title       -> EntryState.title
        + Feed.link        -> Entry.link
        + Feed.author      -> Entry.author
        + Feed.contributor -> Entry.contributor
        + Feed.tagline     -> EntryState.summary

By packaging the info from a Feed into an Entry, we simplify the model 
and also gain a little, allowing pictures in the header of a feed for 
example, as BlogEd does.

There are a few other simplifcations that come to mind, and 
clarifications that are required, in the area of what exactly the Link 
class is about.

One of the simplifications comes to light when one notices an 
interesting symmetry between the Feed and the Entry object in the above 
diagram. Both have contributor and author links pointing to a Person 
object, and both have a link object. This leads one to the contemplate 
the following simplified model where the Feed class inherits from the 
Entry class.

In this model we are thinking of a Feed as an Entry that points to 
entries which constitute the content of the feed. In the previous model 
we were thinking of a Feed as a Set of Entries, plus a few other 
properties. Now an Entry in this second model could never be more than 
one Feed, and this may be considered a limitation. There may be other 
constraints that come to light when I flesh out what exactly a Link is.

In the meantime I thought that maybe this may spark off some 
interesting ideas.

Henry Story
http://bblfish.net/