sparql query get instances of sub classes

Question

I have a simple n3 ontology

 @prefix my: <http://www.codeproject.com/KB/recipes/n3_notation#>.
    @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
    @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .



        my:spec a rdfs:Class.
        my:security a rdfs:Class; rdfs:subClassOf my:spec .

        my:bluetooth a my:security;
        my:preferedby my:BusinessPerson;
        my:name "bluetooth".

im trying to define class specand define security class as a subclass of spec.

this is my sparql query im using with the help of dotNetRdf library

PREFIX my: <http://www.codeproject.com/KB/recipes/n3_notation#>
    PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> 
SELECT ?name WHERE {
    [ a rdfs:subClassOf*/my:spec;
        my:preferedby my:BusinessPerson;
        my:name ?name].
}

im using dotnetrdf library to query my ontology and

Graph g2 = new Graph();
        g2.LoadFromFile(@"C:\\Users\Ravindu Kottahachchi\Desktop\ontology.n3");
        ISparqlDataset ds = new InMemoryDataset(g2);
        LeviathanQueryProcessor processor = new LeviathanQueryProcessor(ds);
        SparqlResultSet resul = processor.ProcessQuery(query1)  as SparqlResultSet;

this setup works fine if i query queries without using any tokens to indicate path cardinality

but when i run the above mentioned query it gives the error VDS.RDF.Parsing.Tokens.MultiplyToken' Token which is valid only after a Predicate to indicate Path Cardinality

is it something wrong with the dotnetrdf setup im using ?

i used this

    TripleStore store = new TripleStore();
            Graph g = new Graph();
            Notation3Parser parser = new Notation3Parser();
            parser.Load(g, @"C:\\Users\Ravindu Kottahachchi\Desktop\ontology.n3");
            store.Add(g);

            SparqlQueryParser sparqlparser = new SparqlQueryParser();
SparqlResultSet results = store.ExecuteQuery(query) as SparqlResultSet;

which uses triple store with the same sparql query but it also gave the same error

can someone help me with where i have made the mistake thanks in advance