Friday, April 29, 2005

We Need Core Data

Something like Apple's new Core Data data-model-framework is long overdue, but we need a standard, free, cross-platform implementation.

The hierarchical filesystem is not meeting our needs. For all of our documents, we want:
  • easy persistence
  • undo and redo
  • gui prototyping
  • revision control
  • transactions
  • search
  • annotation
(Core Data only provides the first few features.)

This new API can't handle behavior and stay language/platform independent. That is, it can't support the object oriented approach of only allowing access to state through member functions.

On the other hand, it would be nice to use regular oop languages to specify the model.

Thursday, April 21, 2005

Justification of Python Sequence Subscripts

Which notation should be used for slicing a subsequence of m through n items?
  1. myseq[ m : n ]
  2. myseq[ m : n+1 ]
  3. myseq[ m-1 : n ]
  4. myseq[ m-1 : n+1 ]
#3 and #4 are silly, because they're inconsistent with the natural way to refer to a single item myseq[m].

Perl and ruby use #1, which is wrong because you can't iterate down to an empty subsequence with myseq[m:m]. Representing this with myseq[m:m-1] is clearly evil, and it breaks completely for m = 0.

The rationale for indices starting from 0 instead of 1 isn't as strong: that representing the whole list as myseq[0:len(myseq)] is "nicer" than representing it as myseq[1:len(myseq)+1]. Perl and ruby don't even have this rationale :).

Ironically, reverse indices do go from 1 to n+1, or rather from -1 to -(n+1). This is fortuitous, because representing reversed(myseq) with myseq[-1::-1] is nicer than representing it with myseq[0::-1]

inspired by a note from Dykstra

Wednesday, April 20, 2005

Type, Effect, and Inference

Effect systems are nice for the same reasons that Type systems are nice, and they're also a big win for concurrency and for encapsulation. Effects, as I understand them, allow specifying how code reads and writes state.

If you're wondering how to convince people to create even more code annotation, don't worry; we'll be able to infer effect information from the code itself, just as we can infer type information from the code itself.

Even with perfect inference, explicit annotation will be useful for external data and for specifying contracts.

Thursday, April 07, 2005

RDF and the WWW

Just had an epiphany: RDF is very similar to the world wide web.

They're both edge-labelled directed graphs.

Though people generally aren't so careful with their link texts, these are just like RDF predicates. The linking page is the subject, and the linked page is the object.

Tomboy and the Future

Tomboy is an excellent program for linux.

It looks like a simple implementation of post-it notes, but it has a few features which make it wonderful:
  • automatic save
  • ability to easily link any text to a new note (sort of like a wiki)
  • fast full search
  • clickable web links
There are more features that'd yield incredible power:
  1. "who links to me?" button
  2. ability to list nodes that are linked to by all of a set of nodes
  3. ability to open a node by path, with autocompletion
  4. "publish" button, for a single node or for a group of nodes
  5. ability to manage the graph graphically
#2 would enable the now fashionable folksonomy functionality.
#3 would replace bookmarks.
#4 would implement a blog authoring tool.
#5 would give you a mindmap.

This stuff shouldn't be in a particular application, but should be available to the whole system. It'll be great if this notes application demonstrates of the power of the approach, and motivates people to implement it more widely.

Monday, April 04, 2005

Corporate Personhood

Here's my attempt to distill the issue of corporate personhood. The best book on the subject that I've seen is The Corporation : The Pathological Pursuit of Profit and Power, by Joel Bakan.

Corporations are disproportionately powerful, because they concentrate huge amounts of money and therefore political influence. Is this good or bad? On the one hand, "what's good for GE is good for America." On the other hand, corporations by law must pursue no objective over maximizing shareholder value. This means externalizing costs whenever possible. For example, a corporation sells 100,000,000 widgets whose use will kill 100 people. That corporation may not legally settle for a smaller profit in order to make its widgets safer, and thereby save the 100 people. (The "what's good for GE" proponents may counter that the public sector makes such cold-hearted calculations all the time, and that the economic activity of the widgets is part of the "rising tide that lifts all boats," making the whole society wealthier and safer.)

What does this have to do with "corporate personhood?" Corporations concentrate huge amounts of capital, but they defuse almost all responsibility. When a corporation makes a million dollars, that money is shared by all its owners. When a corporation kills a person, that guilt is claimed by no one.

Though a corporation is fundamentally no more than a financial partnership, the existence of the corporate entity insulates its officers from morality and from the law. A bad action could spring from the combined actions of many members of a corporation, though none of the individual actions is bad. Even when a single member performs a bad action on behalf of the corporation, it's difficult to detect and prosecute. This insulation itself encourages bad behavior, because members' responsibility to the corporation is more pressing than their responsibility to the society and its laws.

Basing the rights of the corporation on the rights of the person gives corporations additional power. The law gives individuals various rights to protect them from the power of the state (e.g. the Bill of Rights). Sharing these rights with corporations gives them even more power. Treating people and corporations the same allows using a rhetoric of "freedom" to weaken and eliminate regulation, when regulation is the best tool for making corporations consider important externalities, and the only way to correct market failures.

Friday, April 01, 2005

Emulating maxdepth for Solaris find

Say you want to find files in the top level of a directory that meet a certain condition (e.g. haven't been accessed for at least three days).

GNU find can do this with "-maxdepth 1", but Solaris find can't. To get the same functionality for Solaris find, you can use this hack:
find /some/path/. \( -type d -a \! -name . -prune \) -o -type f -print

That is, first prune all directories that aren't named ".", then print the names of the remaining files. It's important that the path be "/some/path/." instead of "/some/path", because that's what enables special treatment for the top level directory.