Subject: RE: [xsl] A theoretical question From: "Ray Lukas" <rlukas@xxxxxxxxxxx> Date: Thu, 1 Mar 2001 10:33:12 -0500 |
No problem my friend: I am also just learning this stuff. I don't know what your ultimate goal is in the XML universe of technology. I myself an big into Java and so I found a pretty good book on Java and XML and of course all of the related technologies. They are quite a few out there now. This book is the Java ad XML book from O'Reilly (ISBN# 0-596-00016-2). It is a pretty good book.. But enough of that. XSL is the Extensible Stylesheet Language. And it is for transforming and translating XML data from one format to another. Okay so what is this other format. It can be almost anything, text output, and even binary output. Well if the output format is some kind of binary format like a PDF (Acrobat Reader) file you would use a Formatting Object in your XSL file. This formatting object does the binary crunching that can produce a PDF file. You can get the specialized formatting object from a lot of places. So that is what a formatting object is for. It takes XML data and converts it into some kind of binary output. So what the heck is XSLT for. Well HTML and XML are not binary they are normal text output. So XSLT can take a XML file and parse it and reformat is into another text based output file, like XML and HTML or any other format you want. I find it helpful to think about XSLT as fancy parser and translator. Getting really good at this stuff is some work. I am on that quest right now. I have several tools which I want to integrate together. XML provides a mean of obtaining data independence. Much like the Java language provides language independence. So each of my tools will accept XML as input and generate XML as output. Output from one tools will then be used by another tool after of course it is formatted (translated) into the correct format for that receiving tool. So XSLT can be used to re-structure one XML file into another XML file. Sometimes my XML might need to go to a user. So XSLT can be used to, instead of generating another XML file to another tool, generate a HTML file for a browser. See what I am saying here. Now a fancy parse like this XSL needs a way to "query and reference" the tags inside of your XML and so there is something called XPath. Now XPath is a specification of its own and defines how a specific items within an XML document can be located (queried). So using this XPath thing you can obtain a series of nodes from the input XML file. It is kind of like getting a record set from a relational database. And the result of this query is even called a "node set". From this node set you generate your output. There is a lot of interesting things that you can do with XPath stuff. Getting some skills in this I think would really be key. The moral is to also try and gain an understanding of XSL, (the general topic) and XPath (the query engine). These two things together seem to be the corner stones. The formatting object stuff you most likely will not need to write since you will almost always use someone else's. Then the final thing, which I plan on using most, is the XSLT stuff which allows you to construct templates. These templates define a set of rules that are applied to your nodeset (remember the XPath stuff). An XSLT file is really a series of these templates. These templates are called over and over and over again by the XSLT processor matching and transforming sections of your XML input file to produce your (text based) output. I know that this all seems really confusing. But have faith and just try and stick with it. I guess that last thing which I want to mention (without writing a book) is there are several XML frameworks which can help you use this stuff. I started working with something called Cocoon. Cocoon is produced by Apache (www.Apache.org). I am, as time permits and it usually doesn't, trying to learn about it. May the Cocoon Gods forgive me but a lot of people have some misery getting this installed and working. I do not know if Apache is the best or even how one would really define what best even means. It all depends. I am just trying to say that it exists and is free and works and is good if you want to learn more. If you need a hand you may call on me. I will try and help you, as best I can. I am not an expert but I am will to try and give you a hand. I hope that this helps you. Ray Lukas RLukas@xxxxxxxxxxx (work) 978.262.6297 (fax) 978.262.6777 -----Original Message----- From: owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx [mailto:owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx] On Behalf Of mcarrasc mcarrasc Sent: Thursday, March 01, 2001 9:05 AM To: Lista XSL Subject: [xsl] A theoretical question Hello! I´m beginning with XSL, and i have a big gap in my small knownledgements :) and I guess you don´t mind to answer me, thanks. I´m really confuse with XSL, XSLT, XSL Formatting Objects.. I don´t know who is who here, because i was searching in the W3C website, and there are recommendations for all of them. What is the difference between XSL and XSL FO? And XSL and XSLT? and all the possible combinations among them :) Thank you very much, and congratulations for your list. It´s very useful. Thanks again. Marta Carrasco _______________________________________________________________ Do You Yahoo!? Envía mensajes instantáneos y recibe alertas de correo con Yahoo! Messenger - http://messenger.yahoo.es XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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