Template XML basics

XML - eXtensible Markup Language - is a text file format with strict formatting rules. XML has quite a lot of capabilities, but for the sake of writing OTLoV templates only very basic XML understanding is required.

File format

Normally, XMLs are stored in files with extension of .xml (OTLoV looks only for .xml files) and a structure of something like (example is taken from Microsoft article):

<?xml version="1.0" encoding="utf-8"?>
<catalog>
    <book id="bk101">
        <author>Gambardella, Matthew</author>
        <title>XML Developer's Guide</title>
        <genre>Computer</genre>
        <price>44.95</price>
        <publish_date>2000-10-01</publish_date>
        <description>An in-depth look at creating applications 
        with XML.</description>
    </book>
    <book id="bk102">
        <author>Ralls, Kim</author>
        <title>Midnight Rain</title>
        <genre>Fantasy</genre>
        <price>5.95</price>
        <publish_date>2000-12-16</publish_date>
        <description>A former architect battles corporate zombies, 
        an evil sorceress, and her own childhood to become queen 
        of the world.</description>
    </book>
    ...
</catalog>

NOTE: ... denotes omitted text.

All XML files should start with a header:

<?xml version="1.0" encoding="utf-8"?>

This line tells that the file is XML, that it uses XML standard version 1.0 and that file encoding is utf-8 (encoding could be omitted, but it's recommended to always state it explicitly).

After the header a root XML element start. XML can have only ONE root element. You can't have more than 1. In sample above the root element is:

<catalog>
    ...
</catalog>

Root element name could be different - it depends on what your application is expecting. For OTLoV that would be:

<Template>
    ...
</Template>

XML elements and attributes

XML file is based on XML elements and their attributes.

Attribute is a property of the element, a simple one, like id="bk101" in the first book element. Attribute value is ALWAYS a text. But the application (or schema, which we are not covering there) could specify that attribute text value must be convertible to specific type, like, an integer number. Then the value of the attribute is still written as text, say id="123", but the app will get it converted to actual number 123, and if the value is not convertible - there could be an error.

For elements XML strictly requires that each element has a start and an end. This is especially important as XML allows children elements (tree) of any depth.

The start of element is always the same, but the end could differ a bit. XML has 2 notations for elements - full and short. Taking sample above the first book element is in full notation:

    <book id="bk101">
        <author>Gambardella, Matthew</author>
        <title>XML Developer's Guide</title>
        <genre>Computer</genre>
        <price>44.95</price>
        <publish_date>2000-10-01</publish_date>
        <description>An in-depth look at creating applications 
        with XML.</description>
    </book>

There a <book is the start of an element and a </book> is the end of the element. The element name is the book, it must be the same in the start and in the end.

What if we don't need extra information and only need the book id? Then we could use short element notation:

    <book id="bk101"/>

Here, a <book is still the start of the element, but the end is denoted with /> instead.

Short element notation does NOT allow children elements. If you need children elements - you must use full notation.

XML & special characters

XML standard reserves some characters for the XML formatting usage only. Also, XML doesn't support standard substitutions, like \n for new line, like \t for tab. Those characters must be substituted in special form. I've aggregated the most commonly used ones:

Character	In XML by name	In XML by dec code	In XML by hex code
< less then	&lt;	&#60;	&#x3C;
> greater then	&gt;	&#62;	&#x3E;
& ampersand	&amp;	&#38;	&#x26;
" double-quote	&quot;	&#34;	&#x22;
' apostrophe	&apos;	&#39;	&#x27;
\t tab		&#9;	&#x9;
\n new line		&#10;	&#xA;