Information Technology Reference
In-Depth Information
is kept. Without a permanent connection,
or with just a poor connection to the data,
users will not be able to finish their work if
the data cannot be accessed.
Solution
: Replicate the data to the user's device
and let the user change the local replica
even when disconnected from the network.
Update the local replicas and distribute
local changes whenever two systems that
hold copies of the data connect.
is received from another client, check it
against those changes that affect the same
shared object and have not yet been ap-
plied by the other client. If performing the
changes will produce a conflict, then undo
or transform one of the changes such that
all clients have a consistent state.
Apart from diverging shared resources, the
n
o m a d i C
o
b j e C t s
can also lead to conflicting
modifications of the same shared resource. Ap-
proaches that automatically resolve conflicts can
only ensure the syntactical but not the semantic
correctness of a shared resource. Therefore,
of-
flineCURE
uses the i
m m u t a b l e
V
e R s i o n s
that keeps
all modifications and lets users manually resolve
the conflicts to ensure semantic correctness. For
resolving conflicts,
offlineCURE
offers a user
interface that displays the conflicts and allows
the users to create a merged version.
In summary,
offlineCURE
enhances the pos-
sibilities for constructing shared knowledge as it
enables users to work nomadically. While being
nomads, users can access shared knowledge and
also construct new knowledge which upon net-
work connection can be integrated in the shared
knowledge repository.
An o
P t i m i s t i C
C
o n C u R R e n C y
C
o n t R o l
approach
ensures that the shared resources can still be
modified via the web interface of
CURE
. As this
approach can lead to diverging shared resources,
offlineCURE
provides means for C
o n F l i C t
d
e t e C
-
t i o n
and synchronizing local shared resources
with the resources stored on the
CURE
server.
offlineCURE
detects resources that have to be
synchronized by using modified bits and compar-
ing the local version number with the most recent
one at the
CURE
server.
o
P t i m i s t i C
C
o n C u R R e n C y
C
o n t R o l
Problem
: You want to ensure consistency but
you want to ensure that changes to the rep-
licated objects are propagated in minimum
time.
Solution
: Perform changes to local replicas im-
mediately. If another client has earlier per-
formed a conflicting change, roll back or
transform your change.
Future reseArCh direCtions
CURE
and its extensions
Fountain of Wisdom
and
offlineCURE
are tools for computer-mediated
interaction. While
CURE
offers basic support for
shared knowledge construction, its extensions
focus on fostering shared knowledge construction
by offering means to establish a community and
to work nomadically.
The design of these tools has been carried out
using patterns for computer-mediated interac-
tion. For this design, high-level as well low-level
patterns have been used. During the design and
development, we experienced that the patterns
served as an educative means both for novice as
well as more experienced developers. The known
C
o n F l i C t
d
e t e C t i o n
Problem
: If two or more users change the same
data at the same time, changes interfere.
This can lead to inconsistent data or con-
tradict the users' intentions. If the users are
unaware of this conflict, they will no lon-
ger have a common base for collaboration.
Solution
: Let each client remember all local
changes that have not yet been applied
by all other clients. Whenever a change
Search WWH ::
Custom Search