Tags and Elements
Tagging content gives the content of a document structure and specific meaning. Each
tag defines an element of the document. For example, compare the following excerpts
from a text file before and after tags have been added.
Original Text File
Coffee house wide shot
17
300
Good
Tagged Document
<clip>
<name>Coffee house wide shot</name>
<reel>17</reel>
<duration>300</duration>
<good>TRUE</good>
</clip>
In the original text file, you have to make assumptions about the meaning of the
numbers 17 and 300. In the tagged document, the tags clarify that 17 is actually the
reel name of a clip and 300 is the clip duration (in frames).
In XML, elements can contain other elements. In the example above, the <clip>
element encompasses all of the other elements.
Most markup languages have a limited set of tags and rules about how the elements
can be ordered hierarchically. For example, an HTML document can have a <p> element
(this is a paragraph element) but if you added a <sentence> element, it would not be
recognized by HTML-aware applications unless the entire HTML standard were altered.
Chapter 11
Using Final Cut Pro XML and QuickTime Metadata
155
II
XML was designed to be extensible—you can define any tags and hierarchical rules
that fit the data you are working with. For example, an XML file that contains store
inventory data might have elements such as <product>, <manufacturer>, <cost>, and
<size>. An XML file that contains video editing information would have very different
elements, such as <clip>, <name>, <duration>, <logginginfo>, and so on.
XML is a strict markup language, which means all tags must be closed. For example, if
your XML document contains a <clip> tag, there must be a corresponding </clip> tag
to close the element. Unclosed tags create errors.