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9.3) GRAS (Research Systems - Other Models - Object-oriented Databases And Vendors)




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This article is from the Object-Oriented Technology FAQ, by Bob Hathaway rjh@geodesic.com with numerous contributions by others.

9.3) GRAS (Research Systems - Other Models - Object-oriented Databases And Vendors)

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GRAS - A Graph-Oriented Database System for SE Applications
Copyright (C) 1987-1993 Lehrstuhl Informatik III, RWTH Aachen
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See the GNU Library General Public License for copyright details.

Contact Adresses:

Dr. Andy Schuerr
Lehrstuhl fuer Informatik III,
University of Technology Aachen (RWTH Aachen),
Ahornstr. 55,
D-5100 Aachen

Email to

andy@i3.informatik.rwth-aachen.de

GRAS is a database system which has been designed according
to the requirements resulting from software engineering
applications. Software development environments are composed
of tools which operate on complex, highly structured data.
In order to model such data in a natural way, we have selected
attributed graphs as GRAS' underlying data model.

A first prototype of the GRAS (GRAph Storage) system - described
in /BL 85/ - was already realized in 1985. Since this time
gradually improving versions of the system have been used at
different sites within the software engineering projects
IPSEN /Na 90/, Rigi /MK 88/, MERLIN /DG 90/, and CADDY /EHH 89/.
Based on these experiences, almost all parts of the original
prototype have been redesigned and reimplemented.

Thus, nowadays a stable and efficiently working single-process
version of the system GRAS with interfaces for the programming
languages Modula-2 and C is available as free software for Sun
workstations (the GRAS system itself is implemented in Modula-2
and consists of many layers which might be reusable for the
implementation of other systems):

Via anonymous ftp from ftp.informatik.rwth-aachen.de
in directory /pub/unix/GRAS in file gras.<version-no>.tar.Z.

There are several files containing documentation, sources, binaries,
application examples, and libraries. All binaries are for Sun/4
machines. Sun/3 binaries are shipped only if explicitly requested.

You have to use the following sequence of operations for installing
the GRAS system at your site:

1) 'ftp ftp.informatik.rwth-aachen.de' (with login name "anonymous"
and password equal to your mail address).
2) 'cd pub/unix/GRAS' (for changing the current directory).
3) 'binary' (command for changing ftp mode).
4) 'get gras.<version-no.>' (use 'ls' for finding the currently used
GRAS version nr.).
5) 'bye' (for exiting ftp).
6) 'uncompress gras.<version-no>.tar'.
7) 'tar xvf gras.<version-no>.tar' (creates a subdirectory GRAS_2 for
the Modula-2 implementation of GRAS including its C-interface).
8) Follow the instructions in file GRAS_2/README.

The current version has programming interfaces for Modula-2 and C
and supports:

- the manipulation of persistent attributed, directed node- and
edge-labeled graphs (including the creation of very long
attributes and of attribute indexes).

- the manipulation of temporary/volatile generic sets/relations/lists,

- the coordination of graph accesses by different GRAS applications
(multiple-read/single-write access with graphs as lock units),

- error recovery based on shadow pages and forward logs,

- nested transactions and linear undo/redo of arbitrarily long
sequences of already committed graph modifying operations based
on forward and backward logs,

- event-handling (with certain kinds of graph-modifications
as events and graph-modifying transactions as event-handlers),

- primitives for version control comprising the capability
for efficiently storing graphs as forward/backward deltas to
other graphs,

- and primitives for declaring graph schemes and for incremental
evaluation of derived attributes.

Furthermore, tools for (un-)compressing graphs and a X11R5-based
graph browser are part of this release.

A multi-process version of the system GRAS supporting the inter-
action of multiple client and multiple server processes within
one local area network is nearby completion (version 6.0/0).

Thus, the GRAS system may be considered to be the core of a graph
oriented DBMS environment. The development of such an environment
based on a very high-level specifications language named PROGRES
is under way (the underlying calculus of this specification language
are so-called PROgrammed GRaph REwriting Systems).

This environment will comprise the following tools (a prerelease
of this environment might be made available upon request):

- a syntax-directed editor for graph schemes, graph rewrite rules,
and sequences of graph rewrite rules,

- an incrementally working consistency checker,

- an incrementally working compiler&interpreter translating
PROGRES specifications into sequences of GRAS procedure
calls (for C as well as for Modula-2),

- and an "enhanced" graph (scheme) browser.

 

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