  In this article, we propose a Category Theory approach to (syntactic)
interoperability between linguistic tools. The resulting category consists of
textual documents, including any linguistic annotations, NLP tools that analyze
texts and add additional linguistic information, and format converters. Format
converters are necessary to make the tools both able to read and to produce
different output formats, which is the key to interoperability. The idea behind
this document is the parallelism between the concepts of composition and
associativity in Category Theory with the NLP pipelines. We show how pipelines
of linguistic tools can be modeled into the conceptual framework of Category
Theory and we successfully apply this method to two real-life examples.
