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MONDRIAN: Make numbers consistent in olap.html;
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	Describe how to create NULL values in an <InlineTable> in schema.html.

[git-p4: depot-paths = "//open/mondrian/": change = 6548]
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julianhyde committed May 11, 2006
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69 changes: 39 additions & 30 deletions doc/olap.html
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Expand Up @@ -11,7 +11,7 @@

<head>
<meta http-equiv="Content-Language" content="en-us">
<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
<meta name="GENERATOR" content="Microsoft FrontPage 6.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Mondrian and OLAP</title>
Expand All @@ -25,8 +25,10 @@ <h1>Mondrian and OLAP</h1>
the MDX language, reading data from a relational database (RDBMS), and presents
the results in a multidimensional format via a Java API. Let's go into what that
means.</p>

<h2>Online Analytical Processing</h2>
<p><dfn><font face="Verdana">Online Analytical Processing (OLAP)</font></dfn>

<p><dfn>Online Analytical Processing (OLAP)</dfn>
means analysing large quantities of data in real-time. Unlike Online Transaction
Processing (OLTP), where typical operations read and modify individual and small
numbers of records, OLAP deals with data in bulk, and operations are generally
Expand All @@ -35,10 +37,11 @@ <h2>Online Analytical Processing</h2>
— the system must respond to queries fast enough to allow an interactive
exploration of the data. As we shall see, that presents considerable technical
challenges.</p>
<p>OLAP employs a technique called <dfn><font face="Verdana">Multidimensional Analysis</font></dfn>. Whereas a

<p>OLAP employs a technique called <dfn>Multidimensional Analysis</dfn>. Whereas a
relational database stores all data in the form of rows and columns, a
multidimensional dataset consists of <dfn><font face="Verdana">axes</font></dfn> and
<dfn><font face="Verdana">cells</font></dfn>. Consider the dataset</p>
multidimensional dataset consists of <dfn>axes</dfn> and
<dfn>cells</dfn>. Consider the dataset</p>
<blockquote>
<table border="2" style="clsStd; border-collapse:collapse" id="AutoNumber1" cellpadding="2" bordercolor="#111111" cellspacing="0">
<tr>
Expand All @@ -58,20 +61,20 @@ <h2>Online Analytical Processing</h2>
</tr>
<tr>
<th nowrap align="left">Total</th>
<td align="right">$17,165</td>
<td align="right">$2,825</td>
<td align="right">$18,867</td>
<td align="right">3,163</td>
<td align="right">10%</td>
<td align="right">$7,073</td>
<td align="right">2,693</td>
<td align="right">$7,636</td>
<td align="right">3,008</td>
<td align="right">8%</td>
<td align="right">12%</td>
</tr>
<tr>
<th nowrap align="left">— Books</th>
<td align="right">$12,845</td>
<td align="right">956</td>
<td align="right">$14,562</td>
<td align="right">1,121</td>
<td align="right">13%</td>
<td align="right">$2,753</td>
<td align="right">824</td>
<td align="right">$3,331</td>
<td align="right">966</td>
<td align="right">21%</td>
<td align="right">17%</td>
</tr>
<tr>
Expand All @@ -80,17 +83,17 @@ <h2>Online Analytical Processing</h2>
<td align="right">424</td>
<td align="right">$1,202</td>
<td align="right">380</td>
<td align="right">16%</td>
<td align="right">37%</td>
<td align="right">-10%</td>
<td align="right">-10%</td>
</tr>
<tr>
<th nowrap align="left">—— Non-fiction</th>
<td align="right">$1,412</td>
<td align="right">400</td>
<td align="right">$1,224</td>
<td align="right">386</td>
<td align="right">11%</td>
<td align="right">2%</td>
<td align="right">$2,129</td>
<td align="right">586</td>
<td align="right">51%</td>
<td align="right">47%</td>
</tr>
<tr>
<th nowrap align="left">— Magazines</th>
Expand All @@ -117,10 +120,11 @@ <h2>Online Analytical Processing</h2>
<p>The rows axis consists of the members 'All products', 'Books', 'Fiction', and
so forth,
and the columns axis consists of the cartesian product of the years '2000' and
'2001', and the <font face="Verdana">calculation</font> 'Growth', and the
'2001', and the calculation 'Growth', and the
<dfn>measures</dfn> 'Unit sales' and 'Dollar sales'. Each cell
represents the sales of a product category in a particular year; for example,
the dollar sales of Magazines in 2001 were $2426.</p>
the dollar sales of Magazines in 2001 were $2,426.</p>

<p>This is a richer view of the data than would be presented by a relational
database. The members of a multidimensional dataset are not always values
from a relational column. 'Total', 'Books' and 'Fiction' are members at
Expand All @@ -130,15 +134,20 @@ <h2>Online Analytical Processing</h2>
a <dfn>calculated member</dfn>, which introduces a
formula for computing cells from other
cells.</p>

<p>The dimensions used here — products, time, and measures — are just three of
many dimensions by which the dataset can be categorized and filtered. The
collection of dimensions, hierarchies and measures is called a <dfn>
<font face="Verdana">cube</font></dfn>.</p>
<p>I hope I have demonstrated that multidimensional is above all a way of <em>
<font face="Verdana">presenting</font></em> data. Although some multidimensional
databases <em><font face="Verdana">store</font></em> the data in multidimensional format,
I shall argue that it is simpler to store the data in relational format. It's
time to look at the architecture of an OLAP system.</p>
collection of dimensions, hierarchies and measures is called a <dfn>cube</dfn>.</p>

<h2>Conclusion</h2>

<p>I hope I have demonstrated that multidimensional is above all a way of <em>presenting</em> data. Although some multidimensional
databases <em>store</em> the data in multidimensional format,
I shall argue that it is simpler to store the data in relational format.</p>

<p>Now it's
time to look at the architecture of an OLAP system. See
<a href="architecture.html">Mondrian architecture</a>.</p>

<hr>

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6 changes: 4 additions & 2 deletions doc/schema.html
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Expand Up @@ -713,15 +713,17 @@ <h4><a name="Inline_tables">Inline tables</a></h4>
<blockquote>

<p><code>&lt;<a href="#XML_Dimension">Dimension</a> name="Severity"&gt;<br>
&nbsp; &lt;<a href="#XML_Hierarchy">Hierarchy</a> hasAll="true"
primaryKey="severity_id"&gt;<br>
&nbsp; &lt;<a href="#XML_Hierarchy">Hierarchy</a> hasAll="true" primaryKey="severity_id"&gt;<br>
&nbsp;&nbsp;&nbsp; &lt;<a href="#XML_InlineTable">Table</a> name=&quot;severity&quot;/&gt;<br>
&nbsp;&nbsp;&nbsp; &lt;<a href="#XML_Level">Level</a> name="Severity"
column="id" nameColumn=&quot;desc&quot; uniqueMembers="true"/&gt;<br>
&nbsp; &lt;/<a href="#XML_Hierarchy">Hierarchy</a>&gt;<br>
&lt;/<a href="#XML_Dimension">Dimension</a>&gt;</code></p>
</blockquote>

<p>To specify a NULL value for a column, omit the <code>&lt;Value&gt;</code> for that
column, and the column's value will default to NULL.</p>

<h4><a name="Member_properties_and_formatters">Member properties and formatters</a></h4>
<p>As we shall see later, a level definition can also define
<a href="#Member_properties">member properties</a> and a
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