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| Re: ROM Feedback: ROM_BASE_ELEMENTS_SPEC [message #1601 is a reply to message #635] |
Wed, 05 January 2005 01:50  |
 Paul Rogers
Messages: 152
Registered: July 2009 |
Senior Member |
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Scott,
Thanks for your detailed comments on the specs. Sorry about the confusion
over the base elements. Your summary is correct. Let's see if I can explain
it better here.
ROM is made up of "report elements". One major category of such elements are
"report items": visual elements that can appear in the report layout. In the
XML implementation, all elements have certain fundamental attributes
represented by the "Design Element" concept. So, the element inheritance
hierarchy is something like:
DesignElement
- Report Element
- - DataSource
- - DataSet
- - ReportItem
- - - Data
- - - Label
- - - List
- - - .
The DesignElement concept handles low-level housekeeping such as holding a
list of properties, defining user-defined properties, holding methods, and
so on. ReportElement is a kind of DesignElement that adds report-specific
attributes such as a name, a base element (for inheritance) and so on.
ReportItem is a kind of ReportElement that adds visual attributes like (x,y)
position, (height,width) size information, style information, and so on.
(By the way, writing this it became clear that we have a confusing naming
ambiguity. There is the "ReportElement" base element, and the "Report"
element at the root of the containment hierarchy. I'll ask the development
team to fix this.)
Elements have two kinds attributes: properties and slots. A property can be
a simple scalar (single-value) such as a color; a list (such as the list of
custom colors), a structure (such as an action), or a list of structures
(such as a highlight rule). (Methods, by the way, are really just scalar
properties whose value is the code for the method.)
The "two base items" in the confusing text of the ROM spec refer to
DesignElement and ReportElement. The "number of structures" refers to
structures used to define certain properties such as actions, user-defined
properties and so on.
Thanks,
- Paul
Paul Rogers
Actuate
BIRT PMC
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