| ROM Feedback: ROM_BASE_ELEMENTS_SPEC [message #635] |
Thu, 30 December 2004 17:15  |
Eclipse User |
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I found the first paragraph of the ROM_BASE_ELEMENTS_SPEC difficult to
understand:
This specification defines the two elements at the root of the report
element hierarchy. The Report Element is the base element for anything that
major components that make up a report. A report item has a name, properties
and so on. The report item element is the base element for all visual report
items and includes data and style information.
This specification also defines a number of structures used by these two
base items.
I have read that section a number of times and it is still a little unclear
what exactly it means. I gather from this that a report is made up of a
number of different components. The majority of those components descend
from the Report Element. One particular type of Report Element is the Report
Item, from which all Visual Report Items descend.
Is this correct?
Scott Rosenbaum
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| Re: ROM Feedback: ROM_BASE_ELEMENTS_SPEC [message #1601 is a reply to message #635] |
Tue, 04 January 2005 20:50  |
| Eclipse User |
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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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