The IFF architecture consists of metalevels, namespaces and meta-ontologies.

• There are three metalevels: top, upper and lower. This partition is permanent. Each metalevel services the level below: the top metalevel services the upper metalevel, the upper metalevel services the lower metalevel, and the lower metalevel services the object-level.

• Within each level, the terminology is partitioned into namespaces (currently represented by PDF documents). The number of namespaces and the content may vary over time: new namespaces may be created or old namespaces may be deprecated, and new terminology and axiomatization within any particular namespace may change (new versions).

• In addition, within each level, various namespaces are collected together into meaningful composites called meta-ontologies (currently represented by HTML documents with links to the contained namespaces). At any particular metalevel, these meta-ontologies cover all the namespaces at that level, but they may overlap. The number of meta-ontologies and the content of any meta-ontology may vary over time: new meta-ontologies may be created or old meta-ontologies may be deprecated, and new namespaces within any particular meta-ontology may change (new versions).

The upper directory structure at the SUO IFF site reflects the architecture of the SUO IFF, with meta-ontologies and namespaces grouped in subdirectories below the metalevel directory in which they are contained. The lowest level directories are used for versioning.  The diagram below gives the SUO IFF directory hierarchy. Note that, amongst other advantages, this new directory structure and file naming does not require a namespace to be attached exclusively to only one meta-ontology.