name="l00263"></a>00263   <span class="keyword">virtual</span> <span class="keywordtype">double</span> emission_cost(<span class="keywordtype">size_t</span> i, <span class="keywordtype">size_t</span> j) <span class="keyword">const</span> = 0;
<a name="l00264"></a>00264 
<a name="l00265"></a>00265   <span class="comment">// return transition cost of [j-th tag at i-th token] to</span>
<a name="l00266"></a>00266   <span class="comment">// [k-th tag at(i+1)-th token]</span>
<a name="l00267"></a>00267   <span cl