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+\chapter{The Big Picture}
+\section{Introduction}
+SQLMap is a simple but complete framework that makes it easy for you to map
+your objects to your SQL statements or stored procedures. The goal of the
+SQLMap framework is to obtain 80\% of data access functionality using only
+20\% of the code.
+
+\section{What does it do?}
+Developers often create maps between objects within an application. One
+definition of a Mapper is an ``object that sets up communication between two
+independent objects.'' A Data Mapper is a ``layer of mappers that moves data
+between objects and a database while keeping them independent of each other
+and the mapper itself.'' [Patterns of Enterprise Architecture, ISBN
+0-321-12742-0].
+
+You provide the database and the objects; SQLMap provides the mapping layer
+that goes between the two.
+
+\section{How does it work?}
+
+Your programming platform already provides a capable library for accessing
+databases, whether through SQL statements or stored procedures. But developers
+find several things are still hard to do well when using ``stock'' PHP
+function including:
+
+Separating SQL code from programming code Passing input parameters to the
+library classes and extracting the output Separating data access classes from
+business logic classes Caching often-used data until it changes Managing
+transactions and many more -- by using XML documents to create a mapping
+between a plain-old object and a SQL statement or a stored procedure. The
+``plain-old object'' can be any PHP object.
+
+\begin{mybox}{Tip:}
+The object does not need to be part of a special object hierarchy or implement
+a special interface. (Which is why we call them ``plain-old'' objects.)
+Whatever you are already using should work just fine.
+\end{mybox}
+
+\begin{figure}[!h]
+    \centering
+        \includegraphics[width=0.65\textwidth]{diagram}
+    \caption{SQLMap DataMapper work flow}
+    \label{fig:diagram}
+\end{figure}
+
+Here's a high level description of the work flow diagrammed by
+Figure~\ref{fig:diagram}: Provide a parameter, either as an object or a
+primitive type. The parameter can be used to set runtime values in your SQL
+statement or stored procedure. If a runtime value is not needed, the parameter
+can be omitted.
+
+Execute the mapping by passing the parameter and the name you gave the
+statement or procedure in your XML descriptor. This step is where the magic
+happens. The framework will prepare the SQL statement or stored procedure, set
+any runtime values using your parameter, execute the procedure or statement,
+and return the result.
+
+In the case of an update, the number of rows affected is returned. In the case
+of a query, a single object, or a collection of objects is returned. Like the
+parameter, the result object, or collection of objects, can be a plain-old
+object or a primitive type.
+
+So, what does all this look like in your source code? Here's how you might
+code the insert of a ``lineItem'' object into your database.
+
+\begin{verbatim}
+TMapper::instance()->insert("InsertLineItem", $lineItem);
+\end{verbatim}
+
+If your database is generating the primary keys, the generated key can be
+returned from the same method call, like this:
+
+\begin{verbatim}
+$myKey = TMapper::instance()->insert("InsertLineItem", $lineItem);
+\end{verbatim}
+
+Example~\ref{example:2.1} shows an XML descriptor for ``InsertLineItem''.
+\begin{example}\label{example:2.1}
+The ``InsertLineItem'' descriptor
+\begin{verbatim}
+<insert id="InsertLineItem" parameterClass="LineItem">
+  INSERT INTO [LinesItem]
+    (Order_Id, LineItem_LineNum, Item_Id, LineItem_Quantity, LineItem_UnitPrice)
+  VALUES
+    (#Order.Id#, #LineNumber#, #Item.Id#, #Quantity#, #Item.ListPrice#)
+ <selectKey type="post" resultClass="int" property="Id" >
+  select @@IDENTITY as value
+ </selectKey>
+</insert>
+\end{verbatim}
+\end{example}
+
+The \tt{<selectKey>} stanza returns an auto-generated key from a SQL Server
+database (for example). If you need to select multiple rows, SQLMap can return
+a list of objects, each mapped to a row in the result set:
+\begin{verbatim}
+$productList = Mapper::instance()->queryForList("selectProduct",$categoryKey);
+\end{verbatim}
+Or just one, if that's all you need:
+\begin{verbatim}
+$product = Mapper::instance()->queryForObject("selectProduct",$categoryKey);
+\end{verbatim}
+
+Of course, there's more, but this is SQLMap from 10,000 meters. (For a longer,
+gentler introduction, see the Tutorial.) Section~\ref{section:3} describes the
+Data Map definition files -- where the statement for ``InsertLineItem'' would
+be defined. The Developers Guide for PHP (Section~\ref{section:4}) describes
+the "bootstrap" configuration file that exposes SQLMap to your application.
+
+\section{Is SQLMap the best choice for my project?}
+SQLMap is a Data Mapping tool. Its role is to map the columns of a database
+query (including a stored procedure) to the properties of an object. If your
+application is based on business objects (including array or lists of
+objects), then SQLMap can be a good choice. SQLMap is an even better choice
+when your application is layered, so that that the business layer is distinct
+from the user-interface layer.
+
+Under these circumstances, another good choice would be an Object/Relational
+Mapping tool (OR/M tool), like [...]. Other products in this category are
+[...] and [...] . An OR/M tool generates all or most of the SQL for you,
+either beforehand or at runtime. These products are called OR/M tools because
+they try to map an object graph to a relational schema.
+
+SQLMap is not an OR/M tool. SQLMap helps you map objects to stored procedures
+or SQL statements. The underlying schema is irrelevant. An OR/M tool is great
+if you can map your objects to tables. But they are not so great if your
+objects are stored as a relational view rather than as a table. If you can
+write a statement or procedure that exposes the columns for your object,
+regardless of how they are stored, SQLMap can do the rest.
+
+So, how do you decide whether to OR/M or to DataMap? As always, the best
+advice is to implement a representative part of your project using either
+approach, and then decide. But, in general, OR/M is a good thing when you
+\begin{itemize}
+  \item Have complete control over your database implementation.
+  \item Do not have a Database Administrator or SQL guru on the team.
+  \item Need to model the problem domain outside the database as an object graph.
+\end{itemize}
+Likewise, the best time to use a Data Mapper, like SQLMap, is when:
+\begin{itemize}
+  \item You do not have complete control over the database implementation, or want to
+continue to access a legacy database as it is being refactored.
+  \item You have database administrators or SQL gurus on the team.
+  \item The database is being used to model the problem domain, and the application's
+primary role is to help the client use the database model.
+\end{itemize}
+
+In the end, you have to decide what's best for your project. If a OR/M tool
+works better for you, that's great! If your next project has different needs,
+then we hope you give SQLMap another look. If SQLMap works for you now:
+Excellent!