[brailleblaster] How semanntic-action files are used in BrailleBlaster
- From: "John J. Boyer" <john.boyer@xxxxxxxxxxxxxxxxx>
- To: brailleblaster@xxxxxxxxxxxxx
- Date: Mon, 22 Oct 2012 06:58:22 -0500
Below is a description of how semantic-action files are used to enable
BraileBlaster to work with any flavor of xml. Note that their format is
completely different from liblouisutdml semantic-action files. I'll try
to get a description of how styles are used out soon.
This is a step-by-step description of how the BrailleBlaster document
model is built and used. It explains the block diagram in more detail.
It begins with an xml file containing utd and a semantic-action file for
that flavor of xml.
The file is parsed to produce a parse tree and then closed. The document
node is pased to a method in the Semantics class.
This method looks for a semantic-action file in the semantics
subdirectory of the programData folder. The name of this file is formed
by adding .sem to the name of the root element. If such a file does not
exist a prototype file containing a line for each distinct markup in the
document is created. A dialog box informs the user of this situation.
The file can later be edited by a developer and added to
BrailleBlaster's repertoire.
An example semantic-action file for dtbook DAISY xml files is shown
below. Note that this file is not a final version, nor is the Semantics
class shown later.
--------------------
newEntries=no
internetAccesRequired=no
book=style document
p=style para
h1=style heading1
h2=style heading2
h3=style heading3
h4=style heading4
h5=style heading4
h6=style heading4
a,href=action htmlLink
a,name=action htmlTarget
code=style computerCode
code,class,inline=action compbrl
em=action italic \s,\s
b=action bold
acronym=action notranslate
li=style list
pagenum=action pagenum
docauthor=style para
doctitle=style heading1
th=style para
tr=style para
strong=action italic \s,\s
code,class,display=style computerCode
note=style note
blockquote=style blockquote
samp=style para
sidebar=style para
br=action softReturn
abbr=style para
--------------------
The semantic-action file is read into an array of the inner class
SemanticEntry, shown below. This array is called semanticTable If no
semantic-action file exists a default semanticTable which will give a
bare-bones display in the print window is built. The display in the
Braille window is defined by the utd part of the document.
--------------------
package newclasses;
public class Semantics {
enum Action {
no,
skip,
generic,
cdata,
htmlLink,
htmlTarget,
document,
para,
heading1,
heading2,
heading3,
heading4,
heading5,
heading6,
heading7,
heading8,
heading9,
heading10,
contentsHeader,
contents1,
contents2,
contents3,
contents4,
conents5,
contents6,
contents7,
contents8,
contents9,
contents10,
noTranslate,
attrToText,
runningHead,
footer,
boxLine,
italic,
bold,
underline,
compbrl,
lineSpacing,
blankLine,
softReturn,
newPage,
brl,
music,
math,
chemistry,
graphic
};
class SemanticEntry {
String markup;
String operation;
String operand;
String parameters;
Action action;
StyleType style;
String macro;
}
SemanticEntry[] semanticTable = new SemanticEntry[100];
}
--------------------
A hashtable is then constructed in which the key is the markup field of
each SementicEntry and the value is its position in the
semanticTable array.
The array is searched for XPath expresions. If they are found they are
applied to the parse tree. Each node in the nodeset is then augmented
with a new attribure, bbsem whose value is the position of the
SemanticEntry in semanticTable
The parse tree is then traversed. If a node does not contain a bbsem
attribute the hash table is used to discover whether it is in the
semanticTable array. First the attributes with their values, together
with the element name are looked up, then just the element name and the
name of each attribute, then just the element name. if any of these
lookups is successful, a bbsem atttribute is added. During this
traversal information on the document, such as whether it references
graphics, is also collected.
This completes the construction of the document model.
BrailleBlaster then calls another method in the Semantics class to
display the document in both the print and Braille windows. In the
Braille window each line of Braille is displayed with proper indentation
and vertical spacing. Tactile images are also displayed. In the print
window the bbsem attribute of each node is used to find the appropriate
entry in the semanticTable. the style, action or macro referenced in
that table is applied. Actions cause methods to be invoked. For example,
such a method might underline a block of characters. Instances of class
StyleType are created the first time a particular style is used. Macros
are compiled the first time they are invoked.
BrailleBlaster then calls a readAndEdit method. If a text node is edited
in the print window it is dynamically retranslated at each character
keystroke in the Braille window. If a new block of characters is created
it is assigned the style para (paragraph), but the user can bring up a
list of valid styles. When a style or action is chosen, the block of
characters is added to the parse treee with the markup in the
corresponding entry in the semanticTable. The entry is found by a linear
search for the style or action name. There may be several entries that
match. The first one is taken. For example, there are several entries in
the dtbok.sem file shown above for the para style. The desired one has
been placed before all the others, which are used to display various
things.
When something in the Braille window is edited the markup to be used for
locking
it is obtained from the semanticTable, as is the markup to be used to
indicate that the corresponding part of the print window is to be
skipped during retranslation.
At any time the user can chose the save menu item. This has two options:
save working (utd) file and save enhanced document. In either case
the save process involves removal of the bbsem attributes. If the save
working document is chosen the parse tree is used to create a file with
the utd extension in the same directory as the original document. If the
save enhanced document option is chosen any edited Braille is moved into
the print part of the document with its appropriate markup. The <brl>
subtrees are deleted and a file with the original document name is
written to the original directory.
If the user choses the Save As menu item s/he can chose a number of
options, among them, save as a brf file and save as pef.
The emboss menu item will send the <brl> portions of the document to the
appropriate embosser driver.
The print menu item will print the document as it is shown in the print
window.
--
John J. Boyer; President, Chief Software Developer
Abilitiessoft, Inc.
http://www.abilitiessoft.com
Madison, Wisconsin USA
Developing software for people with disabilities
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