The retrieval mechanisms of Libertas were very similar to those of Okapi. There were, however, differences. Libertas provided a range of access points for specific item searching as well as subject and classmark searching. Execution of commands required at least two keystrokes - a function or alpha numeric key and the Return key. Search results were displayed as a brief list of titles, and full record details were in ISBD format.
The Okapi '87 features included stemming, spelling standardisation and synonym matching as well as the option of browsing items at the same classification number as relevant items. Like Libertas, users could search for specific items as well as subject areas. Commands were executed using colour coded keys which required only a single keystroke.
Evaluation took the form of interviews with participants being asked to carry out searches on both systems. They were asked to assess the success of each search.
The results showed that while Libertas was favoured for specific item searching and currency, Okapi was better for subject searching. Users preferred Libertas' brief title display when records were retrieved but they liked the format of Okapi's full record displays. Users were critical of Okapi's spelling correction feature. They preferred to correct their own mistakes, rather than have the system offer alternatives.
The next project, Okapi '88 examined the usefulness of a query expansion facility.