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--- at:tutorial:distribution [2009/01/28 17:31] – adding elisag
+++ at:tutorial:distribution [2009/01/28 17:45] – elisag
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 As explained in the previous section, remote far references have been designed to be resilient to intermittent disconnections by default. This behaviour is desirable because it can be expected that many partial failures in mobile ad hoc networks are the result of transient network partitions. However, not all network partitions are transient. For example, a remote device has crashed or has moved out of the wireless communication range and does not return. Such permanent failures should also be dealt by means of compensating actions, e.g. application-level failure handling code.
-To deal with permanent failures, AmbientTalk uses the concept of leasing. A lease denotes the right to access a resource for a speciﬁc duration that is negotiated by the owner of a resource and a resource claimant (called the lease grantor and lease holder, respectively) when the access is ﬁrst requested.  At the discretion of the lease grantor a lease can be renewed, prolonging access to the resource. In AmbientTalk, we represent leases as a special kind of remote far references, which we call leased object references.
+To deal with permanent failures, AmbientTalk uses the concept of leasing. A lease denotes the right to access a resource for a speciﬁc duration that is negotiated by the owner of a resource and a resource claimant (called the lease grantor and lease holder, respectively) when the access is ﬁrst requested.  At the discretion of the lease grantor a lease can be renewed, prolonging access to the resource. In AmbientTalk, we represent leases as a special kind of remote far references, which we call //leased object references//.
 ====Leased Object References====
-A leased object reference is a remote far reference that grants access to a remote object for a limited period of time. When the time period has elapsed, the access to the remote object is terminated and the leased reference is said to expire. Similarly to remote far references, a leased reference abstracts client objects from the actual network connection state. Client objects can send a message to the remote object even if a leased references is disconnected at that time. Message are accumulated in order to be transmitted when the reference becomes reconnected. When the leased reference expires it, messages are discarded since an expired leased reference behaves as a permanently disconnected remote far reference.
+A leased object reference is a remote far reference that grants access to a remote object for a limited period of time. When the time period has elapsed, the access to the remote object is terminated and the leased reference is said to //expire//. Similarly to remote far references, a leased reference abstracts client objects from the actual network connection state. Client objects can send a message to the remote object even if a leased references is disconnected at that time. Message are accumulated in order to be transmitted when the reference becomes reconnected. When the leased reference expires it, messages are discarded since an expired leased reference behaves as a //permanently// disconnected remote far reference. The figure below shows a diagram of the different states of a leased reference.
+{{ :at:tutorial:leasedref-state.png |:at:tutorial:leasedref-state.png}}
 ====Working with leased object references====
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 <note>
-leasedref module exports support primitives to manipulate time intervals (i.e. minutes, seconds, millisecs) so that you do not need to explicitly import the timer module. Remember to exclude those methods from the leasedref import statement if some other module has already imported them, e.g. if futures were imported.
+leasedref module exports support primitives to manipulate time intervals (i.e. minutes, seconds, millisecs) so that you do not need to explicitly import the timer module. Remember to exclude those methods from the leasedref import statement if some other module has already imported them, e.g. if futures are enabled.
 </note>