XML Schema (W3C) - Criticism

Criticism

Although XML Schema is successful in that it has been widely adopted and largely achieves what it set out to, it has been the subject of a great deal of severe criticism, perhaps more so than any other W3C Recommendation.

A good summary of the criticisms is provided by James Clark (who promotes his own alternative, RELAX NG):

  • There are many surprises in the language, for example that restriction of elements works differently from restriction of attributes.
  • The W3C Recommendation itself is extremely difficult to read. Most users find W3Cs XML Schema Primer much easier to understand
  • XSD lacks any formal mathematical specification. (This makes it difficult to reason about schemas, for example to prove that a modification to a schema is backwards compatible.)
  • XSD 1.0 provided no facilities to state that the value or presence of one attribute is dependent on the values or presence of other attributes (so-called co-occurrence constraints). This has been fixed in XSD 1.1.
  • XSD offers very weak support for unordered content.
  • The set of XSD datatypes on offer is highly arbitrary.
  • The two tasks of validation and augmentation (adding type information and default values) should be kept separate.

Read more about this topic:  XML Schema (W3C)

Famous quotes containing the word criticism:

    “... criticism ... makes very little dent upon me, unless I think there is some real justification and something should be done.”
    —Eleanor Roosevelt (1884–1962)

    “The critic lives at second hand. He writes about. The poem, the novel, or the play must be given to him; criticism exists by the grace of other men’s genius. By virtue of style, criticism can itself become literature. But usually this occurs only when the writer is acting as critic of his own work or as outrider to his own poetics, when the criticism of Coleridge is work in progress or that of T.S. Eliot propaganda.”
    —George Steiner (b. 1929)

    “It is ... pathetic to observe the complete lack of imagination on the part of certain employers and men and women of the upper-income levels, equally devoid of experience, equally glib with their criticism ... directed against workers, labor leaders, and other villains and personal devils who are the objects of their dart-throwing. Who doesn’t know the wealthy woman who fulminates against the “idle” workers who just won’t get out and hunt jobs?”
    —Mary Barnett Gilson (1877–?)