CIPA 2005 XX International Symposium, 26 September - 01 October. 2005, Torino, Italv 
939 
Details can not be discussed here. It must be annotated, that the 
DTD will be replaced in future by the more powerful Xschema. 
With XML, XSL and DTD structured information is separated 
from processing: This file structure can be processed with 
object-oriented programming languages in client-server 
environments. 
the menu. 
4. PROCESSING GRAPHIC DATA 
4.1 SVG Scalable Vector Graphics 
3. PARSING XML FILES WITH PHP 
3.1 The Parser 
It is proposed to explain parsing and processing XML- 
documents by using the photogrammetric example from above. 
Requested are the camera values for the camera referenced by 
the description nikon_28. The client's request typed in the 
address line of the browser: 
http://www.imagefact.de/zitadelle-wesel/ 
parse_camera.php?earnera=nikon_28 
has to be submitted to the server. 
A parser will go through the file until the requested camera is 
found. The parser analyses and validates the file structure. 
Expat is an event driven parser and provided by PHP. Events 
are the occurrences of tags and content. An instance of the 
parser is created with the statement: 
$parser = xml_parser_create(); 
It is necessary to set parameter for the parser and handler for the 
elements, for example: 
xml_set_element_handler( $parser, 
"start_element", "end_element" ); 
or 
xml_set_character_data_handler( 
$parser, "inhalt" ); 
start element, end element and inhalX are functions called by 
the parser, if it meets one of the defined events. 
3.2 Processing Data 
The function inhalt will process, if the content of a tag was 
camera. The camera data is stored in arrays. 
function inhalt(Sparser,$data ){ 
global $curr_tag,$index,$camera 
switch ($curr_tag){ 
case "type": $index=$data;break; 
case "ck": $camera[$index][ck]=$data;break; 
case "xh": $camera[$index][xh]=$data;break; 
case "yh": $camera[$index][yh]=$data;break; 
case "al": $camera[$index][al]=$data;break; 
case "a2": $camera[$index][a2]=$data;break; 
case "formX": $camera[$index][formX]= 
$data;break; 
case "formY": $camera[$index][formY]= 
$data;break; 
} 
} 
After getting the camera data, the arrays must be evaluated and 
the requested data, embedded in HTML-tags, has to be 
generated and must be passed to the client. PHP uses the echo- 
function for writing HTML commands. Figure 3 shows the 
answer to a request including image data as rendered by the 
browser. The complete examples can be found on the Web 
under www.programmierpraktikum.de, follow the navigation to 
the readers section (leserbereich), select PHP&XML there from 
Scalable Vector Graphics SVG is the XML formulation of 2D 
vector graphics. It includes drawing of vector data, displaying 
of image data, interaction and animation. Structure and 
appearance of graphic elements is separated by using style 
sheets. 
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Figure 3. Parsing XML-Information and displaying 
the result on a Web page 
Applying a SVG viewer as a plug-in for the Web browser 
enables zooming and panning in the graphic area. Figure 4 
displays the position of control points and demonstrates the use 
of image data inside vector data. 
Figure 4. Image data nd vector data combined with SVG 
The images are rectified and represent to a certain extend a true 
scale image map. Zooming in is followed by loss of quality. 
This is not the case with vector data. The appearance of the 
drawing, shown in figure 5, is dependent from the applied style 
sheet. The file content can be easily transformed to different