Added hyracks-documentation project

git-svn-id: https://hyracks.googlecode.com/svn/branches/hyracks_create_documentation@282 123451ca-8445-de46-9d55-352943316053
diff --git a/hyracks-documentation/src/books/user-guide/doxia-descriptor.xml b/hyracks-documentation/src/books/user-guide/doxia-descriptor.xml
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+<book xmlns="http://maven.apache.org/BOOK/1.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/BOOK/1.0.0 ../../../doxia/doxia-book/target/generated-site/xsd/book-1.0.0.xsd">
+  <id>user-guide</id>
+  <title>Hyracks User Guide</title>
+  <chapters>
+    <chapter>
+      <id>introduction</id>
+      <title>Introduction</title>
+      <sections>
+        <section>
+          <id>intro-whatis</id>
+          <title>What is Hyracks?</title>
+          <file>intro-whatis.apt</file>
+        </section>
+      </sections>
+    </chapter>
+  </chapters>
+</book>
diff --git a/hyracks-documentation/src/books/user-guide/intro-whatis.apt b/hyracks-documentation/src/books/user-guide/intro-whatis.apt
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+What is Hyracks?
+
+  Hyracks is a partitioned-parallel platform for running data-intensive computation on a shared-nothing cluster of commodity machines.
+
+Hyracks Concepts
+
+  Hyracks employs a client-server architecture. On the server side, the software module that is responsible for interacting with clients, keeping track of and dispatching work
+  to other machines in the cluster is called the Hyracks Cluster Controller (CC). There is one CC per logical Hyracks cluster. The module that executes on the worker machine
+  and interacts with the CC to receive work and act on it, is called the Hyracks Node Controller (NC). Every NC in a single Hyracks cluster has a unique logical name. When an
+  NC is started, it is provided the address of the CC whose cluster it must join. Although it is sufficient to run one instance of the NC on a physical machine, it is possible
+  to run multiple instances of NCs (ofcourse each NC has a different logical name) on the same physical machine -- often used for simulating a cluster on a single machine
+  to facilitate testing.
+
+  Hyracks clients interact solely with the CC when submitting their jobs. A Hyracks Job is the unit of work that a client can execute on the Hyracks cluster. A job is expressed
+  as a directed acyclic graph (DAG) of Operators connected to each other by means of Connectors. A more detailed description of jobs, operators, and connectors follows in
+  chapter "Hyracks Jobs".