Domain　ontologies　play　an　important　role　in　knowledge　sharing　and　reuse.　However,　building　such　domain　ontologies　is　a　difficult　task　requiring　many　skills,　especially　when　building　Chinese　domain　ontologies　due　to　the　lack　of　a　complete　methodology.　Ontology　learning　(ontology　extraction,　or　ontology　acquisition)　is　a　subtask　of　information　extraction.　The　goal　of　ontology　learning　is　to　semi-automatically　extract　relevant　concepts　and　relations　from　a　given　corpus　or　other　kinds　of　data　sets　to　form　an　ontology.　This　paper　analyzes　the　state　of　the　art　in　domain　ontology　learning　and　outlines　future　research　directions.