The ICT system description for IWSLT 2008

1.1 Silenus Silenus (Mi et al., 2008; Mi and Huang, 2008) is a forest-based tree-to-string SMT system. A packed parse forest is a compact representation of all derivations (i.e., parse trees) for a given sentence under a context-free grammar. A tree-to-string rule describes the correspondence between a source parse tree and a target string. Unlike previous tree-to-string (Liu et al., 2006; Huang et al., 2006) or string-to-tree models (Galley et al., 2006; Marcu et al., 2006), we extract tree-to-string rules from aligned forest-string pairs. In decoding, the input is a source forest rather than a source tree. Figure 1 demonstrates a pair of linked source forest and target string. Table 1 shows some tree-to-string rules learned from the example forest-string pair in Figure 1.