"[Text Mining] How to feed SGML format file into dictionary?"

Hello, is there any way to load SGML-fomated file into TextInput operator? If not, are there some ways to convert SGML file into other formats to be loaed in TextInput operator? The loaed file will be combined with the dictionary as the following big picture of my experiment below:

<< Big Picture >>

(1) Documents ==> (2) Dictionary Creation ==> (3) Text Representation (based on either the number of the most frequently occurring words in the documents or Boolean, the exisistence of whether a specific topic words are appearing in the documents) ==> (4) Model Induction (e.g. rule-based induction) ==> (5) Document Classfication Rules

The input file is Reuters-21578 Text Catergorization Collection Data Set from UCI Machine Learning Repository, and the data set files are formated with SGM file tag.