Functionalities
To provide support for the playback of temporal spatial data.
At least one of the vector datasets supported by OpenLayers supports time data (GeoRSS). If temporal layers were able to show a highlight/marker for the "current" data point, that marker could be moved according to the "current" date/time.
So, a path of positions could be played to portray "my cycle trek across the Rockies", a growing series of points could how "cities of the world that pass 1 million people", a growing series of polygons could show "countries that broadcast The Simsons", or a scrolling series of points could show "sightings of migrating whales".
Openlayer's perception of the current date/time could be controlled by a slider control (or external html-based control), and displayed in another control.
Interdependencies
None I can think of, it's a new dimension to the data.
Changes to API
As above.
Suggested strategies
It would be quite straightforward to extend the GeoRSS layer. I could botch the time display, and provide a text-based time input.
Hopefully someone with a "higher level" perspective of OpenLayers & software architecture could derive an approach where temporal dependency becomes either an attribute of a map (like spherical mercator), or a consistent component across the APIs.
Hey, I'm only considering temporal vectored data. Temporal tiled (WMS) data is a whole other game.
Alternatives
An array of positions/times could be maintained as a list/table outside OpenLayers. In addition to it's tiled data and a line representing a series of points, OpenLayers could have a single marker. When the user clicks on a position/time, javascript in the wrapper could move the marker to the indicated position - effectively putting a marker on the path at the "current time".
This would certainly be duplicating storage of the position data though, & OpenLayers does provide a tidy, configured place for the storage of the temporal functionality.
Sideaffects & complications
Guess I'm a little to naive in OpenLayers to recognise any at this point.
OpenLayers
