Mendeley API PHP client

Following on from my earlier post about the Mendeley API, I've bundled up my code for OAuth access to the Mendeley API for anyone who's interested in playing with the API using PHP. You can browse the code on Google Code, or grab a tarball here. You'll need a consumer key and a consumer secret from Mendeley for the demos to work, and if you're behind a HTTP proxy you'll have to tweak the code (this is explained in the ReadMe.txt file that comes with the code).

The code is pretty rough, and doesn't use all the Mendeley API calls, but I've other things to do, and it felt like a case of either bundle this up now, or it will get lost among a host of other projects. The Mendeley API still feels woefully under-developed. I'd be more interested in developing this client further if the API was powerful enough to do the kinds of things I'd like to do.

Browsing a digital library using a map

Every so often I revisit the idea of browsing a collection of documents (or specimens, or phylogenies) geographically. It's one thing to display a map of localities for single document (as I did most recently for Zootaxa), it's quite another to browse a large collection.

Today I finally bit the bullet and put something together, which you can see at http://biostor.org/maps/. The website comprises a Google Map showing localities extracted from papers in BioStor, and a list of the papers that have one or more points visible on the map.

In building this I hit a few obstacles. The first is the number of localities involved. I've extracted several thousand point localities from articles in BioStor. Displaying all these on a Google Map is going to be tedious. Fortunately, there's a wonderful library called MarkerCluster, part of the google-maps-utility-library-v3 that handles this problem. MarkerCluster cluster together markers based on zoom level. If you zoom out the markers cluster together, as you zoom in these clusters will start to resolve into their component points. Very, very cool.

The second challenge was to have the list of references update automatically as we move around or zoom in and out on the map. To do this I need to know the bounding box currently being displayed in the map, I can then query the MySQL database underlying BioStor for the localities within the bounding box, using MySQL's spatial extensions. The query is easy enough to implement using ajax, but the trick was knowing when to call it. Initially, listening for the bounds_changed event seemed a good idea. However, this event is fired as the map is being moved (i.e., if the user is panning or dragging the map a whole series of bounds_changed events are fired), whereas what I want is something that signals that the user has stopped moving the map, at which point I can query the database for articles that correspond to the region that map is currently displaying. Turns out that the event I need to listen for is idle (see Issue 1371: map.bounds_changed event fires repeatedly when the map is moving), so I have a function that captures that event and loads the corresponding set of articles.

Another "gotcha" occurs when the region being viewed crosses longitude 180° (or -180°) (see diagram below from http://georss.org/Encodings).

In this case the polygon used to query MySQL would be incorrectly interpreted, so I create two polygons, each with 180° or -180° as one of the boundaries, and merge the articles with points in either of those two polygons.

I've made a short video showing the map in action. Although I've implemented this for BioStor, the code is actually pretty generic, and could easily be adapted to other cases where we want to navigate through a set of objects geographically.

Browsing a digital library using a map from Roderic Page on Vimeo.

Viewing scientific articles on the iPad: the PLoS Reader

Continuing on from my previous post Viewing scientific articles on the iPad: towards a universal article reader, here are some brief notes on the PLoS iPad app that I've previously been critical of.

There are two key things to note about this app. The first is that it uses the page turning metaphor. The article is displayed as a PDF, a page at a time, and the user swipes the page to turn it over. Hence, the app is simulating paper on the iPad screen.

But perhaps more interesting is that, unlike the Nature app discussed earlier, the PLoS app doesn't use a custom API to retrieve articles. Instead the app uses RSS feeds from the PLoS site. PLoS provides journal-specific RSS feeds, as well as subject-specific feeds within journals (see, for example, the PLoS ONE home page). The PLoS Reader app takes these feeds and uses them to create a list of articles the reader can choose from.

A nice feature of the PLoS ATOM feeds is the provision of links to alternative formats for the article (unlike many journal RSS feeds, which provide just a DOI or a URL). For example, the feed item for the article "Transmission of Single HIV-1 Genomes and Dynamics of Early Immune Escape Revealed by Ultra-Deep Sequencing" doi:10.1371/journal.pone.0012303 contains links to the PDF and XML versions of the article:

<link rel="related" 
   type="application/pdf" 
   href="http://www.plosone.org/article/fetchObjectAttachment.action?uri=info:doi/10.1371/journal.pone.0012303&representation=PDF" 
   title="(PDF) Transmission of Single HIV-1 Genomes and Dynamics of Early Immune Escape Revealed by Ultra-Deep Sequencing" />
<link rel="related" 
   type="text/xml" 
   href="http://www.plosone.org/article/fetchObjectAttachment.action?uri=info:doi/10.1371/journal.pone.0012303&representation=XML" 
   title="(XML) Transmission of Single HIV-1 Genomes and Dynamics of Early Immune Escape Revealed by Ultra-Deep Sequencing" />

This makes the task of an article reader much easier. Rather than attempt to screen scrape the article web page, or rely on a rule for constructing the link to the desired file, the feed provides an explicit URL to the different available formats.

I've not seen this feature in other journal RSS feeds, although article web pages sometimes provide this information. BMC journals, for example, provide <link rel="alternate"> tags in the web page for each article, from which we can extract links to the XML and PDF versions, and some journals (BMC included) provide the Google Scholar metadata data tag <meta name="citation_pdf_url"> to link to the PDF. Hence, a generic article reader will need to be able to extract metadata tags from article web pages as it seeks formats suitable to display.