| Summary: | SIS (Semantic Index SYSTEM) can be viewed as an Object Oriented Database Management System (OODBMS) that is based on the knowledge representation language TELOS. TELOS is used both for schema declaration (DDL) and data manipulation (DML) and is based on three abstraction mechanisms: classification, attribution and specialization. Although there is a way to submit queries in SIS through QI (Query Interface), the lack of a high level query language is more than obvious. TELQUEL remedies this situation. TELQUEL is a query language with an SQL-like syntax. Though it is not very rich, it remains expressive and flexible supporting not only relational algebra operations but also transitive closure operations. The implementation of TELQUEL is based on the transformation of a query in a sequence of QI calls. To achieve this goal we had to break down the compilation into two phases. In the first phase we transform the query to a DATALOG program. On second phase we transform the DATALOG program to a sequence of QI calls. In our work special emphasis is given to: 1. The extension of QI so that it can support not only sets, but also relations, and 2. the translation of a query expressed in the declarative language DATALOG to a sequence of QI calls. We also present the syntax and semantics of the language, as well as the way the first phase is performed. Το SIS (Semantic Index System) μπορεί να χαρακτηριστεί ως ένα οντοκεντρικό σύστημα διαχείρισης βάσεων δεδομένων που στηρίζεται στη γλώσσα παράστασης γνώσεων TELOS. Η γλώσσα TELOS χρησιμοποιείται για τον ορισμό του σχήματος (DDL) της βάσης και στηρίζεται σε τρεις μηχανισμούς αφαίρεσης: της ταξινόμησης (classification), της απόδοσης γνωρίσματος (attribution) και της γενίκευσης-εξειδίκευσης (specialization). Αν και στο SIS υπάρχει τρόπος να υποβάλει κάποιος ερωτήσεις μέσω του QI (Query Interface) δεν υπάρχει μια υψηλού επιπέδου ερωτηματική γλώσσα. Το κενό αυτό φιλοδοξεί να αναπληρώσει η TELQUEL. Αν και δεν είναι ιδιαίτερα πλούσια γλώσσα, παραμένει αρκετά εκφραστική και ...
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