Re: Additions to FormNode(?)

• To: Steve Emmerson <steve@xxxxxxxxxxxxxxxx>
• Subject: Re: Additions to FormNode(?)
• From: Dave Glowacki <dglo@xxxxxxxxxxxxx>
• Date: Wed, 18 Mar 1998 14:32:52 -0600

Before I get your dander up on the filename issue, does the "magic number"
part make sense?

I knew the filename method might cause a bit of discussion, but I can't see
any good reason to separate the "magic number" functionality from the
individual fileformat-specific FormNode classes.

> > It'd sure be nice to push the logic from guessFormFromName() into the
> > individual Form classes and augment that with code which recognizes
> > the file type based on the first block.  For example, FITS files always
> > start with "SIMPLE  = ", GIF files always start with "GIF87a" or "GIF89a",
> > etc.
> 
> When I designed the FormNode class I also thought about using naming
> conventions.  I decided not to put such a capability into the FormNode
> class because I thought that a naming-convention capability was somewhat
> orthogonal to the capabilities of the FormNode (or at least
> complementary).  Thus, I figured that such a capability would be better
> off in a class in the user interface that made use of Repositories and
> added naming convention capabilities.

By "user interface", I hope you don't mean core VisAD user-interface
helper classes, not user-developed code.  I certainly wouldn't want to
force every single user to develop a (slightly different) solution to
something like this.

The problem I have with your design is that it moves the implementation
details of a file format into multiple places.  With my two methods,
everything about a file format is still concentrated in one single class.

In fact, I'd propose adding a FormNode method like:

        String[] getDefaultSuffixes()
                return a list of default suffixes for this file format

This could be used as a list of 0 or more defaults by your proposed classes.
This new method would also allow us to implement a common
FormNode.isThisType(String) method, so most file formats wouldn't need to
implement it.

> One thing I think would be crucial to this capability would be the
> ability for the user to customize or modify the naming convention
> (sort of like "mailcap(5)").

Or more appropriately, a reverse ".mime.types" file.

> This would allow different users to have
> different naming conventions.  This would entail considerable more
> effort than implementing FormNodes that lacked this capability, so I
> decided to postpone it.

OK, do you foresee implementing this anytime soon?  I'm being optimistic
and assuming we'll get a big bump in users after next week, all busily
trying to crank out VisAD applications...

• Follow-Ups:
  • Re: Additions to FormNode(?)
    • From: Tom Whittaker

• References:
  • Re: Additions to FormNode(?)
    • From: Steve Emmerson