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| <p class="head">BIRT FAQ</p> |
| <p class="subhead">Report Layout</p> |
| |
| <h1>Report Object Model (ROM)</h1> |
| |
| <h2>Q: What is the ROM?</h2> |
| |
| <p>ROM stands for "Report Object Model." It is the model (or |
| specification) behind BIRT report elements. Just as HTML, CSS and SOAP are |
| standards separate from an implementation, so ROM is a model separate from the |
| BIRT implementation.</p> |
| |
| <p>ROM is the model behind the palette items, property dialogs, |
| methods and so on. ROM consists of a set of core elements, and rules for adding |
| extended elements.</p> |
| |
| <p>Elements can have properties. Properties have a type. Property |
| types include simple ones such a string, number, dimension and so or. Property |
| types also include complex ones such as structures, lists, and lists of |
| structures. For example, static text is defined as a structure with text and a |
| resource key for internationalization.</p> |
| |
| <p>Elements can fit together using "slots". Each element has named |
| slots. For example, the report element has slots for the layout (body), for |
| styles, and so on.</p> |
| |
| <p>Elements can have methods & expressions (code). These are |
| specialized forms of properties.</p> |
| |
| <p>In a later release, elements will be able to inherit from another |
| element. This will allow reuse. For example, you can define a data source in a |
| library, and use it in multiple report designs.</p> |
| |
| <p>ROM provides styles and style properties. ROM's style system is |
| based on CSS, extended for use within a report. Users can create their own |
| styles, or can use many predefined styles. Predefined styles in ROM select |
| specific report items. For example, the "report" style sets defaults for the |
| entire report. As in CSS, styles cascade. Style information set on a container |
| element cascades to its contents.</p> |
| |
| <p>To learn more about ROM, read the ROM Specifications located in |
| the <a href="../ref">reference area</a> of this web site.</p> |
| |
| <h2>Q: What is the XML design file?</h2> |
| |
| <p>BIRT stores your report design in a "design file." This file is |
| in XML format and has a ".rptdesign" suffix. The XML design file is created by |
| the BIRT designer and directly executed by the BIRT engine; there is no |
| compilation step.</p> |
| |
| <h2>Q: What is the ROM schema?</h2> |
| |
| <p>The BIRT XML design file is defined by an XML schema. At present, |
| the schema is located in the BIRT source code in the |
| org.eclipse.birt.report.model project in the src\org\eclipse\birt\report\model\parser\design.xsd |
| file. Eventually, it will move to a well-defined location on the Eclipse web |
| site.</p> |
| |
| <p>The schema is designed to allow extensions. The schema defines |
| syntax that allows extensions to be added to BIRT without making changes to the |
| actual schema. For example, an extended item uses the following tag:</p> |
| |
| <pre class="code-block"><extended-item name="extension"></pre> |
| |
| <p>Properties are in a generic form:</p> |
| |
| <pre class="code-block"><property name="propName">value</property>.</pre> |
| </p> |
| |
| <p>In this sense, the schema describes a syntax for representing |
| report elements in general. The schema does not list the properties, for |
| example; that is defined in a separate rom.def file that is derived from the ROM |
| specification.</p> |
| |
| <h2>Q: What is rom.def?</h2> |
| |
| <p>The ROM schema defines the syntax for the XML design file. The specific set of ROM-defined elements, their slots, and their properties are defined by a separate internal metadata file called rom.def. This file is in the BIRT source code in the org.eclipse.birt.report.model in the src\org\eclipse\birt\report\model\elements\rom.def file.</p> |
| |
| <p>Rom.def contains the information that drives the generic property sheet by defining properties and property types. It also describes JavaScript objects defined by BIRT and other meta-data.</p> |
| |
| <p>The metadata subsystem of the BIRT model provides a Java API to access this information.</p> |
| |
| <h1>Data Display</h1> |
| |
| <h2>Q: How do I display page numbers in HTML or PDF?</h2><p>BIRT uses Apache FOP to convert a report to PDF. FOP does |
| pagination and assigns page numbers. As a result, there is no JavaScript |
| expression you can use to get the current page number. Instead, BIRT will add a |
| new "page number" element. It will include a special marker string that tells |
| BIRT or FO where to insert the page number. BIRT will interpret the string when |
| converting to HTML, and will convert the marker to the required FO syntax when |
| converting to PDF using FOP.</p> |
| <p>The element will allow you to say something like:</p> |
| |
| <pre class="code-block">Page $page of $count</pre> |
| |
| <p>At runtime, this will be replaced by:</p> |
| |
| <pre class="code-block">Page 1 of 5</pre> |
| |
| <p class="caution"><span class="caution-head">Release 1.0M2 Note:</span> The |
| page number element has not yet been released. Syntax is still subject to |
| change.</p> |
| |
| <h2>Q: How do I display today's Date?</h2> |
| <p>Add a data item. For the expression, enter:</p> |
| <pre class="code-block">new Date( );</pre> |
| <p>Then, in the Format page of the Property Editor, choose the date |
| format you prefer, such as Medium Date for a display of Apr 15, 2005.</p> |
| |
| <h2>Q: How do I display the row number?</h2> |
| |
| <p>Suppose you want to display a list of items, along with the row |
| number of each. BIRT provides the row variable that gives data for the current |
| data row. row[0] provides the 0-based row index. You can display a 1-based count |
| as follows:</p> |
| |
| <pre class="code-block">row[0] + 1;</pre> |
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