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Making KML Simple For The iPad

I've been involved this summer in some exciting work with Development Seed on bringing their mapping technologies to the iPad. This has included their gorgeous MapBox tile sets, but also third-party data from the internet in the form of KML and GeoRSS. These are each file formats for exchanging geographic information along with content.

GeoRSS is pretty straightforward -- it's basically regular RSS but with a small amount of geographic information added in the form of extra tags such as <georss:point>. KML, however, is a completely different sort of format, written from the ground up for geographic data. It's probably most commonly known as the format that Google Earth uses to exchange geo info. Beyond Google Earth, it has been used in some exciting applications, from Development Seed's own Maps on a Stick tool to The Jane Goodall Institute's Gombe Chimpanzee Blog, which attaches KML data to every blog entry as a way to give it context and to allow the reader to explore the story a bit more.

Once I got started on the iPad work, however, I noticed that there basically was no parsing library for KML on Apple's iOS platform -- iPhones and iPads. Google puts the definitive library, libkml. It's written in C++ (a minor setback) but it also depends on libexpat, something that exists on Mac OS X but not on iOS.

That aside, I thought that it would also be nice to have a Cocoa-native KML parsing library, something that speaks in native Objective-C types like UIImage for icons and UIColor for colors without the need for conversion. So I wrote one!

This library, Simple KML, is now available as open source under the New BSD License, licensed jointly by Development Seed and Code Sorcery Workshop. You can find a basic usage overview in the features summary.

While Simple KML does make KML very simple to parse, it does not do any drawing for you. It's important to note that you will have to take the placemarks, styles, and structures in the KML documents that you wish to display and write your own drawing to display them. This could be on Apple's MapKit mapping library built into the SDK, external mapping libraries, or perhaps your own drawing on static map images. Simple KML just makes it easy to turn a KML file or a KMZ archive into data structures native to Cocoa for use in your own graphics work.

Since Simple KML is open source, I'd love to have any feedback or contributions that you might have to offer. Simple KML is up on GitHub, allowing anyone to create a free account, fork the project, and send me patches via merge requests.

(Cross-posted on the Development Seed blog)

Hooking into Portland CocoaHeads

I had the opportunity to attend the October meeting of the Portland CocoaHeads club last night and had a great time! I especially liked the location, CubeSpace, and look forward to spending some more time there soon.

My friend Jon Wight of Toxic Software was able to be on this side of the country, too, to demo his, and others', recent work on the Obama iPhone application. Great job, guys! It's a really impressive piece of software, all the more so because it was a volunteer effort and was created in a mere three weeks!

I also did brief demo towards the end of the meeting of my dockless mode hack, just to share it and to get some eyes on the problems I've seen with it.

Lastly, just a note for the curious. When I introduced myself last night, a couple folks mentioned that they had heard of my blog or products, but had no idea I was based in Portland. Well, it's a recent thing, and I haven't tended to talk about travel or personal life much on this blog, but I'm now located just outside of Portland. This year has been a wild ride wherein my wife and I have attempted to live in a number of places, taking advantage of my mobile work ability and our shared wanderlust. Thus far, we've lived in DC, which we sadly left in March after three years, and then in Spain, Cape Cod, and now, the West Coast. I think we'll be staying here for some time, though, especially given a great Cocoa group like CocoaHeads and the vibrant tech (and not to mention, beer) scene in Portland.

Drupal File Taxonomy Server public release!

I've finally been able to make a public, alpha release of the File Taxonomy Server for Drupal 6, allowing integration of a Drupal site's category structure into a drag-and-drop WebDAV interface. I blogged about this software a bit previously, but am finally getting some code out there. If it sounds like something you'd be interested in, then I encourage you to check out the project and give it a spin.

I've fixed a couple minor bugs and now the install instructions mention the latest tested versions of the DAV API and File Framework projects, so it should be pretty easy to get going.

You can create and edit categories and upload and tag files to your site, all from the comfort of your WebDAV client, including Mac OS X's Finder, Windows' Explorer, or other applications like Transmit, Coda, and Cyberduck.

Feedback is welcome, but please report bugs over on the project page, not here. I welcome comments and feedback, but please try to keep official feature requests and bug reports over there.

Major advancements in Drupal file handling

I wanted to mention a few technologies that I've been working with and contributing to lately. This post will be pretty tech-heavy, so I'll throw out some keywords ahead of time so that you can decide if this is something that you'll be interested in reading further: WebDAV, desktop-web integration, RDF, and content-addressable storage, all in the context of my content management system of choice, Drupal.

My work specifically has been in porting and updating some work started by Arto Bendiken (whose projects, it seems, I just start to wrap my head around, and appreciate the foresightedness of, about two years after he himself conceives of them). Aside from writing a guide to his high-traffic caching module, Boost, and porting his debugging tool, Trace, to the latest version of Drupal some time ago, I've been porting his Drupal-WebDAV content bridge, File Server, fixing some bugs in the underlying DAV API, and integrating with the updated File Framework that Arto and my other colleague Miglius Alaburda have been working on.

I'll tackle each of these technologies in layers, starting from what the user sees on down to the gory details under the hood in how the files are stored and queried.

File Server

File Server lets you take a WebDAV client, such as Mac OS X's Finder or Windows Explorer or, better yet, a richer program like Transmit or Cyberduck, login to your Drupal-based website with it using the account that you already have, and drag and drop the files and folders presented there to you. Assuming your Drupal site has file nodes (essentially, chunks of content in the form of file uploads) on it, this dragging and dropping can be used to re-categorize the files, upload new files, and change your site's category structure.

Here's an example:

1) I have a Drupal-based website.

2) I connect to http://my-website-url/dav in a WebDAV client and login with my Drupal user credentials. I'm then presented with a view of my tags:

3) I drag a file from my desktop into a folder corresponding with the tag that I'd like it to be categorized under:

4) When I go to my Drupal site, the file exists as a node and has been tagged appropriately:

This happens via File Server, which I've recently ported to Drupal 6, and Arto's DAV API, which lets you hook all kinds of Drupal facilities into a standardized DAV interface. In this case, we're connecting Drupal's taxonomy (i.e. tags and categories) and in turn, its file nodes, to DAV. It makes a lot of sense here because the files are going into Drupal as file nodes, with automatic conversion into other formats, automatic metadata extraction (as seen in the sidebar above), and automatic indexing into the search system.

File Framework

File Framework is the link between the actual files and the node structure in Drupal. In short, File Framework takes the default facility in Drupal for file uploads and replaces it with a more robust system for backend storage, exporting of info, and conversion into alternative formats. For example, you can upload a PowerPoint presentation and automatically get related nodes out as PNG, PDF, Flash slideshow, and more.

File Framework is a lot of under-the-hood stuff and is in active development for Drupal 6. It also builds upon two other frameworks, RDF and Bitcache.


RDF stands for Resource Description Framework and is not Drupal-specific, though it embodies a concept that Drupal is trying to move towards. RDF is a step in the direction towards the semantic web, where computers can understand what data is about, not just what it contains.

The most common application for this technology is search engine technology. Today, when trying to find a picture, we search for web pages that contain the words picture of a sunset and only turn up hits if those words are found. In the semantic web, this info could be found because the search engine can understand that there is a person who has a name of Joe, who has a profession of professional photographer, and who has a website at, which in turn has a file which is a digital photograph, which has a description containing the word sunset. As a result, some context can be gleaned by the computers indexing all of this stuff, such as the fact that this likely to be a good photo of a sunset since Joe is a professional photographer, and can provide much richer info than the search engine merely looking for words that the content author may or may not have written near the object in question.

Anyway, RDF is the stuff that stores these triples, the idea of subject-predicate-object, e.g., website has a file. Arto has hacked together an API for RDF storage in Drupal and the File Framework now uses it. This RDF storage facilitates not only descriptiveness on the site, but also helps with cross-site searches when this data is needed.

None of this stuff is useful if people have to focus on creating the RDF, so this RDF API combined with Drupal makes it easy for people to keep doing what they were doing before and have the system take care of all of this context stuff.


Bitcache is a means for content-addressable storage (CAS), which means that, unlike most filesystems that we deal with today, the address or URL pointing to a file is based merely on the content, not on the set location. To put it another way, when you put a file on your hard drive, it gets an address like file:///users/justin/myfile.txt that is assigned arbitrarily (well, actually by you based on how you name it and where you put it, but it's arbitrarily related to the actual content). In Bitcache, a unique string of letters is calculated when the file is put into the system and as long as the content remains the same, the pointer URL to that file will remain unchanged. When the file changes, a new copy is created which necessarily has a different address; however, the old file remains in the system as well. So, a benefit is that a given file that exists in a given state is never put into the system twice, since it can be continually referred to by its content address. Another benefit is that the old versions are necessarily retained for archival purposes as well.

A quick hypothetical example: a computer server is in use by an office of people to store their MP3 collections on. When someone puts a new song on the server, it gets a content address. When a second person later puts the same song on the server, a second copy is not created -- instead, the second person gets a reference to the original file's address, since the file is the same anyway. That way, half the storage is used. As more people add the same song to their collections, the storage benefit increases. This is a simplified and contrived example, but it's the basic gist of things.

The File Framwork for Drupal makes use of Arto's Bitcache project. So, when you are using the stack of tools I've been talking about here, under it all, you also get the benefits of CAS behind the scenes.


I'm going to stop there, as I'm sure I've done some grave injustice to some of the complexity involved, left out some of the cons that come with the pros of these systems, and I've probably mangled some of the descriptions too. But then again, that's why I'm working on a piece of it and not the whole thing ;-)

I get excited about this stuff not just because of the Cool Factor™, but also because this sort of thing, when combined with Drupal 6's capabilities in the workflow department with triggers and actions, can lead to some powerful publishing and conversion capabilities for file uploads. And all of this paves the way for Drupal to be the most forward-thinking content management system out there.

Questions? Comments? Corrections? Leave a note below and let's sort it out.

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