A single application or tool may play the role of reader, writer and/or checker.
A SKOS reader is a tool or application that takes as input a KOS represented using SKOS (in some concrete syntax, e.g. RDF/XML, turtle, N3 etc.), and parses that representation into some internal data structure. This document says nothing about what the tool must do with that data structure, or whether the data structure should conform to any standard. A SKOS reader is expected to accept all of the SKOS vocabulary, but may not necessarily provide internal representation for all constructs (for example, not all readers may fully understand/represent Collections). SKOS Writer
A SKOS writer is a tool or application that is able to provide as output a SKOS representation of a KOS in an appropriate concrete syntax (e.g. RDF/XML, turtle, N3 etc.). The SKOS representation produced should respect the semantic conditions as given in the SKOS reference. Note that, depending on the internals of the application, a SKOS writer may not make use of all the SKOS vocabulary -- for example a simple hierarchy sketch-pad may just produce concept hierarchies using hierarchical semantic relations and lexical labels. SKOS Checker
A SKOS checker is a tool or application that takes as input a KOS represented using SKOS (in some concrete syntax, e.g. RDF/XML, turtle, N3 etc.) and returns either true or false, depending on whether the SKOS representation provided respects the semantic conditions as given in the SKOS reference. A SKOS checker is expected to understand all of the SKOS core vocabulary. If the document does not respect the conditions, a detailed report may be provided. This document provides no statement as to how such a report should represented.
Draft Text, tables, formats etc. for SKOS Implementation report.