The storage component of ADL contains the collection of digital objects (DOBJ's). Apart from physical support for storage of DOBJ's, key aspects of DOBJ's are the binary representation of the information of interest (``data''); a universal object identifier ( oid); and procedures for interpreting/retrieving the data. In relation to the WP, we focus largely on the issue of oid's, although we discuss the ADL collections and their physical storage.
The initial collections of ADL
(i.e. the ``data'' of the DOBJ's)
are focused on
spatially-referenced materials such as
digitized maps, digitized air photos,
and images from many domains of application
[5].
Such items are typically characterized by a
spatial footprint, which is a set of points
characterizing the spatial extent of the item
in the space over which the item is defined
.
While the set of points comprising a footprint
may be of arbitrary shape, it is
frequently represented by a polygon (especially a rectangle)
or by a union of non-intersecting polygons
.
We note that many ``features'' represented
in maps and images, such as towns and valleys,
also have well-defined footprints.
We are extending the basic collections to include textual materials that reference objects possessing spatial footprints.