Relation of CEX data to CitableCollection data structures

In CEX, a table of data is represented by two blocks: the citeproperties block describes schemas, while the citedata block contains the table of data.

In addition, collections may be cataloged with further metadata in a citecollections block.

The CitableCollection package can instantiate four kinds of objects from a CEX source.

1. a PropertyDefinition defines name and data type of a single property or field of a data table. This can be created from a single line of a citeproperties block.
2. a RawDataCollection associates the data from a citedata block with a schema. If CEX source includes schema information for a given collection, the schema for the RawDataCollection is built using that. If the citedata block does not have associated citeproperties information, a schema is inferred.
3. a CiteCollectionCatalog catalogs one or more data sets with metadata associated with the collection as a whole, incuding a label or description, licensing information, and information about natural ordering, if any, of the data set.
4. a CatalogedDataCollection unites a single entry from a CiteCollectionCatalog with a RawDataCollection.