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The basic structure of a PSEE
has a DBMS at its core and all of the tools of the environment form
a layer around it.
EPOS extendes such a model by having three layers around its
The EPOSDB [Mun93] is a client-server DBMS. It provides the
uniform versioning (according to the change oriented paradigm,
RIFERIMENTO) and an object-oriented data model.
All the accesses to the database are performed within long,
nested and cooperating transactions .
Every transaction is connected to a
corresponding file-based workspace. The data are extracted from the
database ( check-out) at the beginning of the transaction. When it
commits (i.e. when it ends regularly), the modified data are put
back again ( check-in).
Here are the three layers surrounding the EPOSDB:
- A reflexive and fully object-oriented PML, called SPELL
that unifies and extends the Data Definition Language (DDL) and Data
Manipulation Language (DML) of the underlying database.
SPELL employs the Object-Oriented [Rum87] paradigm.
This layer supports the Analysis/Design meta-activity (PM2).
Figure 1.1: The layered architecture of EPOS
- A Tasking Framework for the definition and concurrent
execution of task networks, with associated tools and humans
(meta-activity PM4). The execution is performed the Execution
Manager (one per transaction) which invokes external tools through a
Broadcast Message Server (BMS).
- Application or domain-specific process models. They
include both Process Schemas. Application specific types gives the
meta-tool (mainly Execution Manager and Planner) the domain
knowledge for enacting the process model.
All activities and products are described through SPELL.
Mon Feb 20 21:59:27 MET 1995