// the YML homepage

include homepage.en.yhtml2

page "YML – Why a Markup Language?!" {
    h1 > Introduction

    p   >>
        Modelling approaches like ¬http://en.wikipedia.org/wiki/Oslo_(Microsoft) Microsoft Oslo¬
        or ¬http://www.eclipse.org/modeling/emf/ Eclipse Modeling Framework¬ are trying to reach the
        situation, that a programmer can define what he wants to have, and not only how to implement
        it technically.
        >>

    p   >>
        Both projects are doing this in a complex way. With the CodeGen project, I'm trying to
        provide a generation framework plain and simple.
        >>

    p   >>
        Because one of the problems to solve is a possibility to quickly define Domain Specific
        Languages and to work with them, I created YML. YML is very easy to use – but it does not
        do the complete job itself. As a matter of fact, I'm leveraging most of the features from
        the XML toolchain.
        >>

    p   >>
        XML has the possibilities to do the job of creating Domain Specific Languages already;
        so my approach is to make these features fit in a concept for Declarative Programming
        and Code Generation.
        >>

    h2 id=xml > XML – a language to design languages already there

    p   >>
        Any time a ¬http://en.wikipedia.org/wiki/Formal_language formal language¬ is created for
        ¬http://en.wikipedia.org/wiki/Computing computing¬, a compromise has to be found: whether
        the language is perfect for the computer but terrible for the human or vice versa.
        ¬http://www.w3.org/XML/ XML¬ is very good for the computer ;-)
        >>

    p   >>
        Using XML for the reasons mentioned above, but for
        ¬http://en.wikipedia.org/wiki/Computer_programming programming¬? “Why a
        ¬http://en.wikipedia.org/wiki/Markup_language Markup Language¬?!”
        was what I was shouting some time playing around with a
        ¬http://en.wikipedia.org/wiki/Automatic_programming code generator¬ in
        ¬http://www.w3.org/TR/xslt XSLT¬. That gave the idea.
        >>

    h2 id=motivation > Motivation

    p   >>
        Many people don't write XSLT directly, because they don't like writing programs in angle
        brackets. The result usually is, that people are writing ¬http://java.sun.com Java¬ programs,
        and are processing XML from Java, or are using XSLT features from Java programs.
        >>

    p   >>
        But that is very inefficient – there are small and quick XSLT processors, and there are
        no advantages at all to implement that in Java or ¬http://en.wikipedia.org/wiki/C++ C++¬
        usually.
        >>

    p   >>
        So I wanted to have something like a Java or
        ¬http://en.wikipedia.org/wiki/C_(programming_language) C¬ like language, which can be easily
        translated into XSLT. Then a common XSLT processor can process the program, and XML can
        be processed very quickly (see also the ¬yslt#sample YSLT sample program¬).
        >>

    p   >>
        I started this, because I saw, that code generation for Automated Software Engineering
        can be implemented very easily in XSLT – but writing XSLT is annoying.
        >>

    h2 id=what > What can I do with YML?

    p > With YML you can:

    ul {
        li p > use a C-like ¬http://en.wikipedia.org/wiki/Domain-specific_language DSL¬ without writing a grammar first
        li p > generate code out of this ¬http://en.wikipedia.org/wiki/Domain-specific_language DSL¬ using ¬yslt YSLT¬
        li p > generate code out of ¬http://en.wikipedia.org/wiki/Unified_Modeling_Language UML¬ using ¬yslt YSLT¬ on ¬http://en.wikipedia.org/wiki/XML_Metadata_Interchange XMI¬
        li p > generate code out of any XML based language like ¬http://en.wikipedia.org/wiki/Scalable_Vector_Graphics SVG¬ using ¬yslt YSLT¬
        li p > define a ¬http://en.wikipedia.org/wiki/Wiki wiki¬ like language in just a few lines like ¬http://fdik.org/yml/programming#wiki YHTML¬ does
        li p > replace bad designed and complicated XML languages with simpler C-like ones
        li p > ... and much more.
    }

    h2 id=howitworks > How it works: Replacing angle brackets with some Python

    p > Just writing down what I wanted to have instead of XML for a sample:

    Code    ||
            <list name="List of goods">
                <head>
                    <columTitle>
                        Goods
                    </columnTitle>
                    <columnTitle>
                        Price
                    </columnTitle>
                </head>
                <row>
                    <value>
                        Beer
                    </value>
                    <value>
                        20
                    </value>
                </row>
                <row>
                    <value>
                        Wine
                    </value>
                    <value>
                        30
                    </value>
                </row>
            </list>
            ||

    p > Something like that should be more easy, say, like this:

    Code    ||
            list "List of goods" {
                head {
                    title > Goods
                    title > Price
                }
                row {
                    value > Beer
                    value > 20
                }
                row {
                    value > Wine
                    value > 30
                }
            }
            ||

    h2 id=ylanguages > Y Languages

    p   >>
        The latter is what I call an Y language – a language specified in YML. How could this be
        achieved? Well, what's to do? To have the required information, how to build XML from the
        script above, we need:
        >>

    ul {
        li  >>
            the information, that “list of goods” is an attribute named «name», while «Goods» is
            the text value of a tag
            >>
        li > «title» shout be written out as «columnTitle»
    }

    p > How to do that? Let's invent a simple definition language for that information:

    Code    ||
            decl list(name);
            decl title alias columnTitle;
            ||

    p > Here you can ¬samples/list.yml2 download the complete list sample¬.

    div id=bottom > ¬#top ^Top^¬ ¬programming >> Using YML 2¬ ¬index.en.yhtml2 (source)¬
}