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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
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<html> <head>
<title>Using the Real-time Extension in CIAO</title>
</head>
<body>
<h1>Using the Real-time Extension in CIAO</h1>
<!-- ============================================================ -->
<h3>Abstract</H3>
The real-time extension support in CIAO enables application developers
to deploy real-time applications by specifying real-time
configurations as XML descriptors without modifying the component
implementation. In fact, embedding the real-time configuration
policies in component implementations decrease the reusability of the
software components.
Different types of real-time policy can be applied at different
stage of the component development lifecycle, e.g.,
<ul>
<li>Component implementation
<li>Component packaging
<li>Application composition
<li>Target platform configuration
<li>Deployment configuration
</ul>
Real-time policies can also be applied to various scope in an
applications, e.g., many real-time policies can be associate with some
or all of the following ORB mechanisms:
<ul>
<li>ORBs
<li>POAs
<li>Threads
<li>Object references
</ul>
<!-- ============================================================ -->
<h3>CIAO's Real-time Extension</h3>
CIAO extends CCM's assembly descriptor to support the specifications
of real-time policies. This mechanism allows you to allocate
resources that are global to a RTComponentServer and to define real-time
policies required by a component installation. Currently, CIAO
support configuration of certain real-time policies at the POA level,
i.e., in CCM's terminology, the container level. These policies
include:
<ol>
<li>Priority Model Policy
<li>Threadpool Policy
<li>Banded Connection Policy
</ol>
The kind of resources that are global to a RT component server that CIAO
real-time extension specifies include:
<ol>
<li>Threadpool
<li>Threadpool with lanes
<li>Connection bands
</ol>
<!-- ============================================================ -->
<h3>Using the CIAO Real-time Extension</h3>
Application developers can define the aforementioned Real-Time
extension Descriptor (.rtd file) that CIAO defines to allocate
resources and specify real-time policies. The Document Type
Definition (DTD) for the real-time extension description is defined in
this <a href="XML/ciao_rt_cad_ext.dtd">file</a>. Each .RTD file
specifies the required resources and the policy definitions within a
RTComponentServer.
A RTComponentServer can be associated to a .RTD file. This is done by
using the "extension" element with "class" attributed set to
"RT-CAD-EXT", within a processcollocation or hostcollocation element.
Here is an example:
<code><pre>
<processcollocation>
.
.
.
<extension class="RT-CAD-EXT" origin="CIAO">somefile.rtd</extension>
.
</processcollocation>
</pre></code>
Each .RTD file contains the two major subelements:
<ul>
<li><rtresources>: defines all the RT resources the assciating
RTComponentServer should provide.
<li><rtpolicysets>: defines named collections of policies
(<rtpolicyset>) that apply to component installations in
the RTComponentServer.
</ul>
The <rtpolicyset>'s defined in the .RTD file can be associated
to a component installation, i.e., a component placement within the
RTComponentServer to which the .RTD file is associated. For example,
<code><pre>
<homeplacement>
.
.
,
<extension class="RT-POLICY-SET"
origin="CIAO">A_POLICY_NAME</extension>
.
</homeplacement>
</pre></code>
<h3>Future Addition</h3>
As mentioned earlier, RT policies can be applied at various stages of
component-based deployment lifecycle and at different scope. For
example, applying RTpolicies at the ORB level, or at the object
reference level of a component receptacle. These extensions involve
at least, extending the "appropriate" XML descriptor definition and
extending the CIAO runtime, including core and/or the CIDL generated
code to configure the policies. How other RT-related policies can be
added will be reviewed in my thesis available shortly.
<hr>
<address>Nanbor Wang</address>
<!-- hhmts start -->
Last modified: Sun Nov 30 19:23:25 Mountain Standard Time 2003
<!-- hhmts end -->
</body> </html>
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