Exemplo n.º 1
0
        protected internal virtual ICollection <string> FeaturesCpC <_T0>(PaddedList <_T0> cInfo, int loc)
            where _T0 : CoreLabel
        {
            ICollection <string> features = new List <string>();
            CoreLabel            c        = cInfo[loc];
            CoreLabel            c2       = cInfo[loc + 1];
            CoreLabel            c3       = cInfo[loc + 2];
            CoreLabel            p        = cInfo[loc - 1];
            CoreLabel            p2       = cInfo[loc - 2];
            CoreLabel            p3       = cInfo[loc - 3];
            string charc   = c.GetString <CoreAnnotations.CharAnnotation>();
            string charc2  = c2.GetString <CoreAnnotations.CharAnnotation>();
            string charc3  = c3.GetString <CoreAnnotations.CharAnnotation>();
            string charp   = p.GetString <CoreAnnotations.CharAnnotation>();
            string charp2  = p2.GetString <CoreAnnotations.CharAnnotation>();
            string charp3  = p3.GetString <CoreAnnotations.CharAnnotation>();
            int    cI      = c.Get(typeof(CoreAnnotations.UTypeAnnotation));
            string uTypec  = (cI != null ? cI.ToString() : string.Empty);
            int    c2I     = c2.Get(typeof(CoreAnnotations.UTypeAnnotation));
            string uTypec2 = (c2I != null ? c2I.ToString() : string.Empty);
            int    c3I     = c3.Get(typeof(CoreAnnotations.UTypeAnnotation));
            string uTypec3 = (c3I != null ? c3I.ToString() : string.Empty);
            int    pI      = p.Get(typeof(CoreAnnotations.UTypeAnnotation));
            string uTypep  = (pI != null ? pI.ToString() : string.Empty);
            int    p2I     = p2.Get(typeof(CoreAnnotations.UTypeAnnotation));
            string uTypep2 = (p2I != null ? p2I.ToString() : string.Empty);

            if (flags.dictionary != null || flags.serializedDictionary != null)
            {
                DictionaryFeaturesCpC(typeof(CoreAnnotations.LBeginAnnotation), typeof(CoreAnnotations.LMiddleAnnotation), typeof(CoreAnnotations.LEndAnnotation), string.Empty, features, p2, p, c, c2);
            }
            if (flags.dictionary2 != null)
            {
                DictionaryFeaturesCpC(typeof(CoreAnnotations.D2_LBeginAnnotation), typeof(CoreAnnotations.D2_LMiddleAnnotation), typeof(CoreAnnotations.D2_LEndAnnotation), "-D2-", features, p2, p, c, c2);
            }

            /*
             * N-gram features. N is upto 2.
             */
            if (flags.useWord2)
            {
                // features.add(charc +"c");
                // features.add(charc2+"c2");
                // features.add(charp +"p");
                // features.add(charp + charc  +"pc");
                // features.add(charc + charc2  +"cc2");
                // // cdm: need hyphen so you can see which of charp or charc2 is null....
                // features.add(charp + "-" + charc2 + "pc2");
                features.Add(charc + "::c");
                features.Add(charc2 + "::c1");
                features.Add(charp + "::p");
                features.Add(charp2 + "::p2");
                // trying to restore the features that Huihsin described in SIGHAN 2005 paper
                features.Add(charc + charc2 + "::cn");
                // (*)
                features.Add(charp + charc + "::pc");
                features.Add(charp + charc2 + "::pn");
                features.Add(charp2 + charp + "::p2p");
                features.Add(charp2 + charc + "::p2c");
                features.Add(charc2 + charc + "::n2c");
            }
            // todo: this is messed up: Same as one above at (*); should be cn2 = charc + charc3 + "::cn2"
            if (flags.useFeaturesCpC4gram || flags.useFeaturesCpC5gram || flags.useFeaturesCpC6gram)
            {
                // todo: Both these features duplicate ones already in useWord2
                features.Add(charp2 + charp + "p2p");
                features.Add(charp2 + "p2");
            }
            if (flags.useFeaturesCpC5gram || flags.useFeaturesCpC6gram)
            {
                features.Add(charc3 + "c3");
                features.Add(charc2 + charc3 + "c2c3");
            }
            if (flags.useFeaturesCpC6gram)
            {
                features.Add(charp3 + "p3");
                features.Add(charp3 + charp2 + "p3p2");
            }
            if (flags.useGoodForNamesCpC)
            {
                // these 2 features should be distinctively good at biasing from
                // picking up a Chinese family name in the p2 or p3 positions:
                // familyName X X startWord AND familyName X startWord
                // But actually they seem to have negative value.
                features.Add(charp2 + "p2");
                features.Add(charp3 + "p3");
            }
            if (flags.useUnicodeType || flags.useUnicodeType4gram || flags.useUnicodeType5gram)
            {
                features.Add(uTypep + "-" + uTypec + "-" + uTypec2 + "-uType3");
            }
            if (flags.useUnicodeType4gram || flags.useUnicodeType5gram)
            {
                features.Add(uTypep2 + "-" + uTypep + "-" + uTypec + "-" + uTypec2 + "-uType4");
            }
            if (flags.useUnicodeType5gram)
            {
                features.Add(uTypep2 + "-" + uTypep + "-" + uTypec + "-" + uTypec2 + "-" + uTypec3 + "-uType5");
            }
            if (flags.useWordUTypeConjunctions2)
            {
                features.Add(uTypep + charc + "putcc");
                features.Add(charp + uTypec + "pccut");
            }
            if (flags.useWordUTypeConjunctions3)
            {
                features.Add(uTypep2 + uTypep + charc + "p2utputcc");
                features.Add(uTypep + charc + uTypec2 + "putccc2ut");
                features.Add(charc + uTypec2 + uTypec3 + "ccc2utc3ut");
            }
            if (flags.useUnicodeBlock)
            {
                features.Add(p.GetString <CoreAnnotations.UBlockAnnotation>() + "-" + c.GetString <CoreAnnotations.UBlockAnnotation>() + "-" + c2.GetString <CoreAnnotations.UBlockAnnotation>() + "-uBlock");
            }
            if (flags.useShapeStrings)
            {
                if (flags.useShapeStrings1)
                {
                    features.Add(p.GetString <CoreAnnotations.ShapeAnnotation>() + "ps");
                    features.Add(c.GetString <CoreAnnotations.ShapeAnnotation>() + "cs");
                    features.Add(c2.GetString <CoreAnnotations.ShapeAnnotation>() + "c2s");
                }
                if (flags.useShapeStrings3)
                {
                    features.Add(p.GetString <CoreAnnotations.ShapeAnnotation>() + c.GetString <CoreAnnotations.ShapeAnnotation>() + c2.GetString <CoreAnnotations.ShapeAnnotation>() + "pscsc2s");
                }
                if (flags.useShapeStrings4)
                {
                    features.Add(p2.GetString <CoreAnnotations.ShapeAnnotation>() + p.GetString <CoreAnnotations.ShapeAnnotation>() + c.GetString <CoreAnnotations.ShapeAnnotation>() + c2.GetString <CoreAnnotations.ShapeAnnotation>() + "p2spscsc2s");
                }
                if (flags.useShapeStrings5)
                {
                    features.Add(p2.GetString <CoreAnnotations.ShapeAnnotation>() + p.GetString <CoreAnnotations.ShapeAnnotation>() + c.GetString <CoreAnnotations.ShapeAnnotation>() + c2.GetString <CoreAnnotations.ShapeAnnotation>() + c3.GetString <CoreAnnotations.ShapeAnnotation
                                                                                                                                                                                                                                                         >() + "p2spscsc2sc3s");
                }
                if (flags.useWordShapeConjunctions2)
                {
                    features.Add(p.GetString <CoreAnnotations.ShapeAnnotation>() + charc + "pscc");
                    features.Add(charp + c.GetString <CoreAnnotations.ShapeAnnotation>() + "pccs");
                }
                if (flags.useWordShapeConjunctions3)
                {
                    features.Add(p2.GetString <CoreAnnotations.ShapeAnnotation>() + p.GetString <CoreAnnotations.ShapeAnnotation>() + charc + "p2spscc");
                    features.Add(p.GetString <CoreAnnotations.ShapeAnnotation>() + charc + c2.GetString <CoreAnnotations.ShapeAnnotation>() + "psccc2s");
                    features.Add(charc + c2.GetString <CoreAnnotations.ShapeAnnotation>() + c3.GetString <CoreAnnotations.ShapeAnnotation>() + "ccc2sc3s");
                }
            }

            /*
             * Radical N-gram features. N is upto 4.
             * Smoothing method of N-gram, because there are too many characters in Chinese.
             * (It works better than N-gram when they are used individually. less sparse)
             */
            char rcharc;
            char rcharc2;
            char rcharp;
            char rcharp2;

            if (charc.Length == 0)
            {
                rcharc = 'n';
            }
            else
            {
                rcharc = RadicalMap.GetRadical(charc[0]);
            }
            if (charc2.Length == 0)
            {
                rcharc2 = 'n';
            }
            else
            {
                rcharc2 = RadicalMap.GetRadical(charc2[0]);
            }
            if (charp.Length == 0)
            {
                rcharp = 'n';
            }
            else
            {
                rcharp = RadicalMap.GetRadical(charp[0]);
            }
            if (charp2.Length == 0)
            {
                rcharp2 = 'n';
            }
            else
            {
                rcharp2 = RadicalMap.GetRadical(charp2[0]);
            }
            if (flags.useRad2)
            {
                features.Add(rcharc + "rc");
                features.Add(rcharc2 + "rc2");
                features.Add(rcharp + "rp");
                features.Add(rcharp + rcharc + "rprc");
                features.Add(rcharc + rcharc2 + "rcrc2");
                features.Add(rcharp + rcharc + rcharc2 + "rprcrc2");
            }
            if (flags.useRad2b)
            {
                features.Add(rcharc + "rc");
                features.Add(rcharc2 + "rc2");
                features.Add(rcharp + "rp");
                features.Add(rcharp + rcharc + "rprc");
                features.Add(rcharc + rcharc2 + "rcrc2");
                features.Add(rcharp2 + rcharp + "rp2rp");
            }

            /* Non-word dictionary: SEEN bi-gram marked as non-word.
             * This is frickin' useful.  I hadn't realized.  CDM Oct 2007.
             */
            if (flags.useDict2)
            {
                NonDict2 nd = new NonDict2(flags);
                features.Add(nd.CheckDic(charp + charc, flags) + "nondict");
            }
            if (flags.useOutDict2)
            {
                if (outDict == null)
                {
                    CreateOutDict();
                }
                features.Add(outDict.GetW(charp + charc) + "outdict");
                // -1 0
                features.Add(outDict.GetW(charc + charc2) + "outdict");
                // 0 1
                features.Add(outDict.GetW(charp2 + charp) + "outdict");
                // -2 -1
                features.Add(outDict.GetW(charp2 + charp + charc) + "outdict");
                // -2 -1 0
                features.Add(outDict.GetW(charp3 + charp2 + charp) + "outdict");
                // -3 -2 -1
                features.Add(outDict.GetW(charp + charc + charc2) + "outdict");
                // -1 0 1
                features.Add(outDict.GetW(charc + charc2 + charc3) + "outdict");
                // 0 1 2
                features.Add(outDict.GetW(charp + charc + charc2 + charc3) + "outdict");
            }
            // -1 0 1 2

            /*
             * (CTB/ASBC/HK/PK/MSR) POS information of each characters.
             * If a character falls into some function categories,
             * it is very likely there is a boundary.
             * A lot of Chinese function words belong to single characters.
             * This feature is also good for numbers and punctuations.
             * DE* are grouped into DE.
             */
            if (flags.useCTBChar2 || flags.useASBCChar2 || flags.useHKChar2 || flags.usePKChar2 || flags.useMSRChar2)
            {
                string[] tagsets;
                // the "useChPos" now only works for CTB and PK
                if (flags.useChPos)
                {
                    if (flags.useCTBChar2)
                    {
                        tagsets = new string[] { "AD", "AS", "BA", "CC", "CD", "CS", "DE", "DT", "ETC", "IJ", "JJ", "LB", "LC", "M", "NN", "NR", "NT", "OD", "P", "PN", "PU", "SB", "SP", "VA", "VC", "VE", "VV" };
                    }
                    else
                    {
                        if (flags.usePKChar2)
                        {
                            //tagsets = new String[]{"r", "j", "t", "a", "nz", "l", "vn", "i", "m", "ns", "nr", "v", "n", "q", "Ng", "b", "d", "nt"};
                            tagsets = new string[] { "2", "3", "4" };
                        }
                        else
                        {
                            throw new Exception("only support settings for CTB and PK now.");
                        }
                    }
                }
                else
                {
                    //logger.info("Using Derived features");
                    tagsets = new string[] { "2", "3", "4" };
                }
                if (taDetector == null)
                {
                    CreateTADetector();
                }
                foreach (string tag in tagsets)
                {
                    features.Add(taDetector.CheckDic(tag + "p", charp) + taDetector.CheckDic(tag + "i", charp) + taDetector.CheckDic(tag + "s", charc) + taDetector.CheckInDic(charp) + taDetector.CheckInDic(charc) + tag + "prep-sufc");
                }
            }
            //features.add("|ctbchar2");

            /*
             * In error analysis, we found English words and numbers are often separated.
             * Rule 1: isNumber feature: check if the current and previous char is a number.
             * Rule 2: Disambiguation of time point and time duration.
             * Rule 3: isEnglish feature: check if the current and previous character is an english letter.
             * Rule 4: English name feature: check if the current char is a conjunct pu for English first and last name, since there is no space between two names.
             * Most of PUs are a good indicator for word boundary, but - and .  is a strong indicator that there is no boundry within a previous , a follow char and it.
             */
            if (flags.useRule2)
            {
                /* Reduplication features */
                // previous character == current character
                if (charp.Equals(charc))
                {
                    features.Add("11-R2");
                }
                // previous character == next character
                if (charp.Equals(charc2))
                {
                    features.Add("22-R2");
                }
                // current character == next next character
                // fire only when usePk and useHk are both false.
                // Notice: this should be (almost) the same as the "22" feature, but we keep it for now.
                if (!flags.usePk && !flags.useHk)
                {
                    if (charc.Equals(charc2))
                    {
                        features.Add("33-R2");
                    }
                }
                char cur1 = ' ';
                char cur2 = ' ';
                char cur  = ' ';
                char pre  = ' ';
                // actually their length must be either 0 or 1
                if (charc2.Length > 0)
                {
                    cur1 = charc2[0];
                }
                if (charc3.Length > 0)
                {
                    cur2 = charc3[0];
                }
                if (charc.Length > 0)
                {
                    cur = charc[0];
                }
                if (charp.Length > 0)
                {
                    pre = charp[0];
                }
                string prer = rcharp.ToString();
                // the radical of previous character
                Pattern E  = Pattern.Compile("[a-zA-Z]");
                Pattern N  = Pattern.Compile("[0-9]");
                Matcher m  = E.Matcher(charp);
                Matcher ce = E.Matcher(charc);
                Matcher pe = E.Matcher(charp2);
                Matcher cn = N.Matcher(charc);
                Matcher pn = N.Matcher(charp2);
                // if current and previous characters are numbers...
                if (cur >= '0' && cur <= '9' && pre >= '0' && pre <= '9')
                {
                    if (cur == '9' && pre == '1' && cur1 == '9' && cur2 >= '0' && cur2 <= '9')
                    {
                        //199x
                        features.Add("YR-R2");
                    }
                    else
                    {
                        features.Add("2N-R2");
                    }
                }
                else
                {
                    // if current and previous characters are not both numbers
                    // but previous char is a number
                    // i.e. patterns like "1N" , "2A", etc
                    if (pre >= '0' && pre <= '9')
                    {
                        features.Add("1N-R2");
                    }
                    else
                    {
                        // if previous character is an English character
                        if (m.Matches())
                        {
                            features.Add("E-R2");
                        }
                        else
                        {
                            // if the previous character contains no radical (and it exist)
                            if (prer.Equals(".") && charp.Length == 1)
                            {
                                if (ce.Matches())
                                {
                                    features.Add("PU+E-R2");
                                }
                                if (pe.Matches())
                                {
                                    features.Add("E+PU-R2");
                                }
                                if (cn.Matches())
                                {
                                    features.Add("PU+N-R2");
                                }
                                if (pn.Matches())
                                {
                                    features.Add("N+PU-R2");
                                }
                                features.Add("PU-R2");
                            }
                        }
                    }
                }
                string engType = IsEnglish(charp, charc);
                string engPU   = IsEngPU(charp);
                if (!engType.Equals(string.Empty))
                {
                    features.Add(engType);
                }
                if (!engPU.Equals(string.Empty) && !engType.Equals(string.Empty))
                {
                    StringBuilder sb = new StringBuilder();
                    sb.Append(engPU).Append(engType).Append("R2");
                    features.Add(sb.ToString());
                }
            }
            //end of use rule
            // features using "Character.getType" information!
            string origS = c.GetString <CoreAnnotations.OriginalCharAnnotation>();
            char   origC = ' ';

            if (origS.Length > 0)
            {
                origC = origS[0];
            }
            int type = char.GetType(origC);

            switch (type)
            {
            case char.UppercaseLetter:
            case char.LowercaseLetter:
            {
                // A-Z and full-width A-Z
                // a-z and full-width a-z
                features.Add("CHARTYPE-LETTER");
                break;
            }

            case char.DecimalDigitNumber:
            {
                features.Add("CHARTYPE-DECIMAL_DIGIT_NUMBER");
                break;
            }

            case char.OtherLetter:
            {
                // mostly chinese chars
                features.Add("CHARTYPE-OTHER_LETTER");
                break;
            }

            default:
            {
                // other types
                features.Add("CHARTYPE-MISC");
                break;
            }
            }
            features.Add("cliqueCpC");
            return(features);
        }
Exemplo n.º 2
0
        public virtual ICollection <string> FeaturesCpC(PaddedList <IN> cInfo, int loc)
        {
            ICollection <string> features = new List <string>();
            CoreLabel            c        = cInfo[loc];
            CoreLabel            c1       = cInfo[loc + 1];
            CoreLabel            c2       = cInfo[loc + 2];
            CoreLabel            c3       = cInfo[loc + 3];
            CoreLabel            p        = cInfo[loc - 1];
            CoreLabel            p2       = cInfo[loc - 2];
            CoreLabel            p3       = cInfo[loc - 3];
            string charc = c.Get(typeof(CoreAnnotations.CharAnnotation));

            if (charc == null)
            {
                charc = string.Empty;
            }
            string charc1 = c1.Get(typeof(CoreAnnotations.CharAnnotation));

            if (charc1 == null)
            {
                charc1 = string.Empty;
            }
            string charc2 = c2.Get(typeof(CoreAnnotations.CharAnnotation));

            if (charc2 == null)
            {
                charc2 = string.Empty;
            }
            string charc3 = c3.Get(typeof(CoreAnnotations.CharAnnotation));

            if (charc3 == null)
            {
                charc3 = string.Empty;
            }
            string charp = p.Get(typeof(CoreAnnotations.CharAnnotation));

            if (charp == null)
            {
                charp = string.Empty;
            }
            string charp2 = p2.Get(typeof(CoreAnnotations.CharAnnotation));

            if (charp2 == null)
            {
                charp2 = string.Empty;
            }
            string charp3 = p3.Get(typeof(CoreAnnotations.CharAnnotation));

            if (charp3 == null)
            {
                charp3 = string.Empty;
            }

            /*
             * N-gram features. N is upto 2.
             */
            if (flags.useWord2)
            {
                // features.add(charc +"c");
                // features.add(charc1+"c1");
                // features.add(charp +"p");
                // features.add(charp +charc  +"pc");
                // if( flags.useMsr ){
                //   features.add(charc +charc1 +"cc1");
                //   features.add(charp + charc1 +"pc1");
                // }
                features.Add(charc + "::c");
                features.Add(charc1 + "::c1");
                features.Add(charp + "::p");
                features.Add(charp2 + "::p2");
                // trying to restore the features that Huishin described in SIGHAN 2005 paper
                features.Add(charc + charc1 + "::cn");
                features.Add(charp + charc + "::pc");
                features.Add(charp + charc1 + "::pn");
                features.Add(charp2 + charp + "::p2p");
                features.Add(charp2 + charc + "::p2c");
                features.Add(charc2 + charc + "::n2c");
                features.Add("|word2");
            }

            /*
             * Radical N-gram features. N is upto 4.
             * Smoothing method of N-gram, because there are too many characters in Chinese.
             * (It works better than N-gram when they are used individually. less sparse)
             */
            char rcharc;
            char rcharc1;
            char rcharc2;
            char rcharc3;
            char rcharp;
            char rcharp1;
            char rcharp2;
            char rcharp3;

            if (charc.Length == 0)
            {
                rcharc = 'n';
            }
            else
            {
                rcharc = RadicalMap.GetRadical(charc[0]);
            }
            if (charc1.Length == 0)
            {
                rcharc1 = 'n';
            }
            else
            {
                rcharc1 = RadicalMap.GetRadical(charc1[0]);
            }
            if (charc2.Length == 0)
            {
                rcharc2 = 'n';
            }
            else
            {
                rcharc2 = RadicalMap.GetRadical(charc2[0]);
            }
            if (charc3.Length == 0)
            {
                rcharc3 = 'n';
            }
            else
            {
                rcharc3 = RadicalMap.GetRadical(charc3[0]);
            }
            if (charp.Length == 0)
            {
                rcharp = 'n';
            }
            else
            {
                rcharp = RadicalMap.GetRadical(charp[0]);
            }
            if (charp2.Length == 0)
            {
                rcharp2 = 'n';
            }
            else
            {
                rcharp2 = RadicalMap.GetRadical(charp2[0]);
            }
            if (charp3.Length == 0)
            {
                rcharp3 = 'n';
            }
            else
            {
                rcharp3 = RadicalMap.GetRadical(charp3[0]);
            }
            if (flags.useRad2)
            {
                features.Add(rcharc + "rc");
                features.Add(rcharc1 + "rc1");
                features.Add(rcharp + "rp");
                features.Add(rcharp + rcharc + "rpc");
                features.Add(rcharc + rcharc1 + "rcc1");
                features.Add(rcharp + rcharc + rcharc1 + "rpcc1");
                features.Add("|rad2");
            }
            /* non-word dictionary:SEEM bi-gram marked as non-word */
            if (flags.useDict2)
            {
                NonDict2 nd = new NonDict2(flags);
                features.Add(nd.CheckDic(charp + charc, flags) + "nondict");
                features.Add("|useDict2");
            }
            if (flags.useOutDict2)
            {
                if (outDict == null)
                {
                    logger.Info("reading " + flags.outDict2 + " as a seen lexicon");
                    outDict = new CorpusDictionary(flags.outDict2, true);
                }
                features.Add(outDict.GetW(charp + charc) + "outdict");
                // -1 0
                features.Add(outDict.GetW(charc + charc1) + "outdict");
                // 0 1
                features.Add(outDict.GetW(charp2 + charp) + "outdict");
                // -2 -1
                features.Add(outDict.GetW(charp2 + charp + charc) + "outdict");
                // -2 -1 0
                features.Add(outDict.GetW(charp3 + charp2 + charp) + "outdict");
                // -3 -2 -1
                features.Add(outDict.GetW(charp + charc + charc1) + "outdict");
                // -1 0 1
                features.Add(outDict.GetW(charc + charc1 + charc2) + "outdict");
                // 0 1 2
                features.Add(outDict.GetW(charp + charc + charc1 + charc2) + "outdict");
            }
            // -1 0 1 2

            /*
             * (CTB/ASBC/HK/PK/MSR) POS information of each characters.
             * If a character falls into some function categories,
             * it is very likely there is a boundary.
             * A lot of Chinese function words belong to single characters.
             * This feature is also good for numbers and punctuations.
             * DE* are grouped into DE.
             */
            if (flags.useCTBChar2 || flags.useASBCChar2 || flags.useHKChar2 || flags.usePKChar2 || flags.useMSRChar2)
            {
                string[] tagsets;
                // the "useChPos" now only works for CTB and PK
                if (flags.useChPos)
                {
                    if (flags.useCTBChar2)
                    {
                        tagsets = new string[] { "AD", "AS", "BA", "CC", "CD", "CS", "DE", "DT", "ETC", "IJ", "JJ", "LB", "LC", "M", "NN", "NR", "NT", "OD", "P", "PN", "PU", "SB", "SP", "VA", "VC", "VE", "VV" };
                    }
                    else
                    {
                        if (flags.usePKChar2)
                        {
                            //tagsets = new String[]{"r", "j", "t", "a", "nz", "l", "vn", "i", "m", "ns", "nr", "v", "n", "q", "Ng", "b", "d", "nt"};
                            tagsets = new string[] { "2", "3", "4" };
                        }
                        else
                        {
                            throw new Exception("only support settings for CTB and PK now.");
                        }
                    }
                }
                else
                {
                    //logger.info("Using Derived features");
                    tagsets = new string[] { "2", "3", "4" };
                }
                if (taDetector == null)
                {
                    taDetector = new TagAffixDetector(flags);
                }
                foreach (string tagset in tagsets)
                {
                    features.Add(taDetector.CheckDic(tagset + "p", charp) + taDetector.CheckDic(tagset + "i", charp) + taDetector.CheckDic(tagset + "s", charc) + taDetector.CheckInDic(charp) + taDetector.CheckInDic(charc) + tagset + "prep-sufc");
                }
            }
            // features.add("|ctbchar2");  // Added a constant feature several times!!

            /*
             * In error analysis, we found English words and numbers are often separated.
             * Rule 1: isNumber feature: check if the current and previous char is a number.
             * Rule 2: Disambiguation of time point and time duration.
             * Rule 3: isEnglish feature: check if the current and previous character is an english letter.
             * Rule 4: English name feature: check if the current char is a conjunct pu for English first and last name, since there is no space between two names.
             * Most of PUs are a good indicator for word boundary, but - and .  is a strong indicator that there is no boundry within a previous , a follow char and it.
             */
            if (flags.useRule2)
            {
                /* Reduplication features */
                // previous character == current character
                if (charp.Equals(charc))
                {
                    features.Add("11");
                }
                // previous character == next character
                if (charp.Equals(charc1))
                {
                    features.Add("22");
                }
                // current character == next next character
                // fire only when usePk and useHk are both false.
                // Notice: this should be (almost) the same as the "22" feature, but we keep it for now.
                if (!flags.usePk && !flags.useHk)
                {
                    if (charc.Equals(charc2))
                    {
                        features.Add("33");
                    }
                }
                char cur1 = ' ';
                char cur2 = ' ';
                char cur  = ' ';
                char pre  = ' ';
                // actually their length must be either 0 or 1
                if (charc1.Length > 0)
                {
                    cur1 = charc1[0];
                }
                if (charc2.Length > 0)
                {
                    cur2 = charc2[0];
                }
                if (charc.Length > 0)
                {
                    cur = charc[0];
                }
                if (charp.Length > 0)
                {
                    pre = charp[0];
                }
                string prer = rcharp.ToString();
                // the radical of previous character
                Pattern E  = Pattern.Compile("[a-zA-Z]");
                Pattern N  = Pattern.Compile("[0-9]");
                Matcher m  = E.Matcher(charp);
                Matcher ce = E.Matcher(charc);
                Matcher pe = E.Matcher(charp2);
                Matcher cn = N.Matcher(charc);
                Matcher pn = N.Matcher(charp2);
                // if current and previous characters are numbers...
                if (cur >= '0' && cur <= '9' && pre >= '0' && pre <= '9')
                {
                    if (cur == '9' && pre == '1' && cur1 == '9' && cur2 >= '0' && cur2 <= '9')
                    {
                        //199x
                        features.Add("YR");
                    }
                    else
                    {
                        features.Add("2N");
                    }
                }
                else
                {
                    // if current and previous characters are not both numbers
                    // but previous char is a number
                    // i.e. patterns like "1N" , "2A", etc
                    if (pre >= '0' && pre <= '9')
                    {
                        features.Add("1N");
                    }
                    else
                    {
                        // if previous character is an English character
                        if (m.Matches())
                        {
                            features.Add("E");
                        }
                        else
                        {
                            // if the previous character contains no radical (and it exist)
                            if (prer.Equals(".") && charp.Length == 1)
                            {
                                // fire only when usePk and useHk are both false. Not sure why. -pichuan
                                if (!flags.useHk && !flags.usePk)
                                {
                                    if (ce.Matches())
                                    {
                                        features.Add("PU+E");
                                    }
                                    if (pe.Matches())
                                    {
                                        features.Add("E+PU");
                                    }
                                    if (cn.Matches())
                                    {
                                        features.Add("PU+N");
                                    }
                                    if (pn.Matches())
                                    {
                                        features.Add("N+PU");
                                    }
                                }
                                features.Add("PU");
                            }
                        }
                    }
                }
                string engType = IsEnglish(charp, charc);
                string engPU   = IsEngPU(charp);
                if (!engType.Equals(string.Empty))
                {
                    features.Add(engType);
                }
                if (!engPU.Equals(string.Empty) && !engType.Equals(string.Empty))
                {
                    features.Add(engPU + engType);
                }
            }
            //end of use rule
            // features using "Character.getType" information!
            string origS = c.Get(typeof(CoreAnnotations.OriginalCharAnnotation));
            char   origC = ' ';

            if (origS.Length > 0)
            {
                origC = origS[0];
            }
            int type = char.GetType(origC);

            switch (type)
            {
            case char.UppercaseLetter:
            case char.LowercaseLetter:
            {
                // A-Z and full-width A-Z
                // a-z and full-width a-z
                features.Add("CHARTYPE-LETTER");
                break;
            }

            case char.DecimalDigitNumber:
            {
                features.Add("CHARTYPE-DECIMAL_DIGIT_NUMBER");
                break;
            }

            case char.OtherLetter:
            {
                // mostly chinese chars
                features.Add("CHARTYPE-OTHER_LETTER");
                break;
            }

            default:
            {
                // other types
                features.Add("CHARTYPE-MISC");
                break;
            }
            }
            return(features);
        }