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At an idealized level, XML is a generic syntax that is amenable to a wide
variety of contexts and domains. Its utility is attributable to the
following qualities:
1) It is text based
Labels, delimiters, and content are encoded as Unicode characters.
Consequence: There are few impedements to transfering XML data across
heterogenous system boundaries. XML documents can be created using simple
text editors.
2) It is well-formed
The syntax can be interpreted unambiguously and without reliance upon rules
of inference.
Consequence: XML parsers are simple and ubiquitous.
3) It is partially self-describing
All content (data) is labeled.
Consequence: Content type can be clearly identified, both by human and
machine. However, semantics are implicit.
4) It is structured
The syntax describes a single-rooted tree.
Consequence: Most real-world content maps well to hierarchies; hierarchies
are also readily grasped by human beings. Thus, XML documents tend to be
human-readable.
At a practical level, XML has some warts:
1) It is text based
Consequence: Not all data is efficiently encoded as characters.
2) It is well-formed
Consequence: Well-formedness is wordy.
3) It is partially self-describing
Consequence: Names alone are often not sufficient to unambigously convey
semantics.
4) It is structured
Consequence: Data retrieval from trees is not always efficient. Some data
cannot be naturally modeled hierarchically.
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