reader who is familiar with database transaction might find this term
misleading. Classical ``ACID'' database transactions have four
The semantics of EPOS transactions does not enforce these properties as
they are at all. The fact that EPOS users deal with database stored
data justifies the use of the term, but the different natures of the
two kind of transactions should be kept in mind troughout the
reading of the thesis.
- Atomicity: a transaction must be accomplished as a whole or
not at all.
- Consistency: the result of a transaction must be predictable
- Isolation: no transaction must interfere with any other
concurrently executing transaction.
- Durability: the result of changes operated by a
transaction must be permanent.
- This term, even
though commonly used within the Object-Orientation community, is
not part of the EPOS terminology and, therefore, is used here only for
sake of clarity. The EPOS counterparts of the term are, obviously,
type and meta-type
- This sintax has not been implemented
yet. The real SPELL consists of Prolog predicates, for the time
Mon Feb 20 21:59:27 MET 1995