Java Reference
In-Depth Information
This approach will influence our deployment model, possibly losing some generality for con-
creteness and usefulness. Together with introducing the AH, we will see more details of our
deployment model, especially those general to the whole model, and not limited to the AH
role.
The Client Environment Concept
The AH could be thought as the interface between the Deployment Server and the
Client
Environment
. As we will see in detail later, the Client Environment is the formal description of
the current configuration of the client platform: hardware plus software and anything else
needed, such as end-user identity and type of connection. We may think of it as an XML file,
for example. We're not interested in its implementation, rather the abstract concept that could
be found in all kinds of software deployments.
2
The Deployment Policies Concept
If the Client Environment defines the current client instance, on the server side we have a set
of policies that define exactly who must install what. These policies, called
Deployment
Policies
,are issued by the Software Owner, who from our point of view often corresponds to
the Software Producer. The
Resolution Phase
is the act of deciding what to do, given what we
have on the client platform (the Client Environment definition), what we are supposed to
deliver (the resources to install), and what we are told to do (the Deployment Policies).
An Example
An example could be the following, expressing in pairs
<attribute, value>
for describing
the Client Environment and in pseudo-code for the Deployment Policies:
Client Environment: <platform, Java-Enabled cell phone>, <type of user,
consumer> , <memory resources,512K Ram>, <license, evaluation>
Deployment Policies:
•Assertion 1.
If (license==”evaluation”) INSTALL “timebomb.jar”
•Assertion 2.
If (platform==” Java-Enabled cell phone” and memory resources>256K)
INSTALL (“core.jar”, “sprites_1.1.jar”,”extensions_2.1.jar”)
This will send four JAR files to the user's cell phone, that, once installed together, will run the
wanted version of the video game chosen by the user (in this example, assertions are thought
to be in an
OR
logical relationship).
