0.16 Hypercities: a case study for the future of scholarly publishing  (Page 3/6)

Technically speaking, HyperCities is a generalizable, easily scalable data model for linking together and publishing geo-temporal content using a unified front-end delivery system and a distributed back-end architecture. HyperCities consists of a geo-temporal markup server and a front-end visualization platform built on the Google Maps/Earth APIs that enable users to explore, manipulate, and contribute to any geographically aware environment. At its core are databases of openly accessible, geo-temporal content defined by KML, a mark-up language chosen because its development is funded by private enterprise (Google) but governed by the Open Geospatial Consortium, which ensures a robust user-base and an open-source development model for specification and implementation. (External Link)   HyperCities generates real-time, KML-based network links connected to geo-temporal content, offering a non-exclusive front-end for contributing to, organizing, and exploring independent repositories. While HyperCities hosts and stores some data locally, it is important to underscore that a central aim of the project is to host metadata connections to content stored and maintained in external repositories and on external servers. These servers range from commercially available platforms (such as Google's 3D warehouse, YouTube and Flickr) to library and archival platforms for maps, oral histories, videos, photograph collections, and other media files.  In this way, HyperCities provides the connective tissue for the community of geo-spatial time travelers by leveraging the extensive development of data repositories and social networks. HyperCities is not a "walled garden"; rather, it is an aggregation and integration platform built to facilitate interoperable, shareable, and embeddable archival objects that are connected though network links and real-time KML feeds.

The HyperCities system architecture follows one of the central trends often identified as Web 2.0: The front-end is almost entirely separated from its back-end, without following the standard model-view-controller architecture frequently used by web applications. Although a web-based platform, HyperCities behaves more like a desktop application because the front-end follows an event-driven programming model rather than a standard webpage submission model. The front-end is written entirely in Javascript/AJAX and makes extensive use of complex event processing and dynamically-generated User Interface components (rather than prewritten HTML). At its core, the HyperCities platform is a collaboration of web services, compiling a combination of digital content from disparate sources through the use of XML/KML and Javascript.  The Google Maps/Earth APIs define a set of JavaScript objects and methods that HyperCities utilizes to put maps on its interface, allowing instant integration of satellite imagery with other layers such as markers, pathways, images, historical maps, 3D objects, and other kinds of data. 

When a user first visits Hypercities, what is shown is a general Google Map zoomed out to show the world with the "historical cities" featured in HyperCities. Each time the user moves the map (zooms in, pans, jumps to a new city) or adjusts the time-bar, the application interacts with one or more external servers without reloading the entire page; instead, only the relevant data (based on spatial and temporal bounding coordinates as well as pre-defined user privileges/permissions) is displayed while the front-end maintains its own state. The server back-end (written in PHP and running off a MySQL database) is limited to pulling new data to display and input any changes a user might make to the objects being displayed. The front-end is almost a complete application itself because it contains all the display logic. This means that it is not only fairly easy to use HyperCities with different data sources, but it is also possible to pull the data from the back-end into any geographically aware environment.