While these languages represent the specifications for the Ontology, they do not represent the real programming languages that are employed like CycL, Ontolingua, F-Logic, etc.,
1. XML: This uses a standard syntax laid down already by the W3C. The code is crisp and easy to write. The DTD can be defined the way it is required. However, this does not offer the flexibility of defining standard classes and then making use of the similar structure repeatedly. XML is easy to use in a program though of course, creating XML data which will have semantics in them is not possible with the existing structure of XML.
2. XOL on the other hand, offers all those features that are present in XML as well as in OIL. XOL employs modelling primitives that are in line with OKBC standards. This is based on XML and uses Ontologies to extend the features. Therefore, it is found that the language is supporting some of the insufficiencies in XML like standard class definition and other structure definitions. With these, the data gets verified and the mistakes in the data are avoided. In addition to these, this also supports extensive slot hierarchies. But however, it does not allow definition of relationships extensively. This makes it a weak relationship modeller. XOL is comfortable where only data is to be represented without any major relationship criterion which is hard to find in knowledge systems.