Describing and retrieving photos using RDF and HTTP

"19 April 2002"

This note describes a project for describing & retrieving (digitized) photos with (RDF) metadata. It describes the RDF schemas, a data-entry program for quickly entering metadata for large numbers of photos, a way to serve the photos and the metadata over HTTP, and some suggestions for search methods to retrieve photos based on their descriptions.

The RDF data is stored in the JPEG file in comment blocks (blocks of type "COM", as defined by ISO DIS 10918-1). According to the JPEG standard, a comment block can contain arbitrary text. There is no way to assign a type to the text. We simply rely on the fact that RDF can easily be distinguished from plain text by heuristics. JPEG limits each comment block to 64K, but there can be as many blocks as necessary, so arbitrary amounts of text can be added. In practice, the descriptions generated by the rdfpic program are typically only a few hundred bytes long.

The rdfpic program could support the Adobe XMP format [XMP].

The rdfpic editor should read & write metadata using HTTP GET & PUT in addition to read & write from the local file system.

1352 Also posted to: Home page . At: 5:27:51 PM  . .
Permalink  Top  Search Google  Technorati
Other title(s) for this story: