private string RelationshipAnalogy(Feature old, Feature newOld, Feature prevOfCurr, Feature current)
        {
            string return_message = "";
            /*Console.WriteLine("old: " + old.Data);
            Console.WriteLine("new: " + newOld.Data);
            Console.WriteLine("relationship: " + old.getRelationshipNeighbor(newOld.Data));
            Console.WriteLine("previous of current: " + prevOfCurr.Data);
            Console.WriteLine("current: " + current.Data);
            Console.WriteLine("relationship: " + prevOfCurr.getRelationshipNeighbor(current.Data));
            */

            // Senten Patterns list - for 3 nodes
            List<string> sentencePatterns = new List<string>();

            Random rnd = new Random();

            //Define A1, B1, A2, B2, R1,and R2.
            //  Node A1 has relationship R1 with node B1.
            //  Node A2 has relaitonship R2 with node B2.
            //  AND R1 and R2 are in the same list inside equivalent_relationship list.
            string a1 = "";
            string b1 = "";
            string a2 = "";
            string b2 = "";
            string r1 = "";
            string r2 = "";

            //Check equivalent and similarity
            bool found = false;
            bool directional = false;
            //Check if the relationship is a directional word.
            if (Directional_Words.Contains(old.getRelationshipNeighbor(newOld.Data))
                || Directional_Words.Contains(newOld.getRelationshipNeighbor(old.Data)))
            {
                directional = true;
            }//end if

            foreach (List<string> list in equivalent_relationships)
            {
                if (found == true) break;
                if ((list.Contains(old.getRelationshipNeighbor(newOld.Data)) && list.Contains(prevOfCurr.getRelationshipNeighbor(current.Data)))
                    || old.getRelationshipNeighbor(newOld.Data).Equals(prevOfCurr.getRelationshipNeighbor(current.Data)))
                {
                    a1 = old.Data;
                    b1 = newOld.Data;
                    a2 = prevOfCurr.Data;
                    b2 = current.Data;
                    r1 = old.getRelationshipNeighbor(newOld.Data);
                    r2 = prevOfCurr.getRelationshipNeighbor(current.Data);
                    found = true;
                }
                else if ((list.Contains(newOld.getRelationshipNeighbor(old.Data)) && list.Contains(current.getRelationshipNeighbor(prevOfCurr.Data)))
                    || newOld.getRelationshipNeighbor(old.Data).Equals(current.getRelationshipNeighbor(prevOfCurr.Data)))
                {
                    a1 = newOld.Data;
                    b1 = old.Data;
                    a2 = current.Data;
                    b2 = prevOfCurr.Data;
                    r1 = newOld.getRelationshipNeighbor(old.Data);
                    r2 = current.getRelationshipNeighbor(prevOfCurr.Data);
                    found = true;
                }
                else if ((list.Contains(newOld.getRelationshipNeighbor(old.Data)) && list.Contains(prevOfCurr.getRelationshipNeighbor(current.Data)))
                    || newOld.getRelationshipNeighbor(old.Data).Equals(prevOfCurr.getRelationshipNeighbor(current.Data)))
                {
                    a1 = newOld.Data;
                    b1 = old.Data;
                    a2 = prevOfCurr.Data;
                    b2 = current.Data;
                    r1 = newOld.getRelationshipNeighbor(old.Data);
                    r2 = prevOfCurr.getRelationshipNeighbor(current.Data);
                    found = true;
                }
                else if ((list.Contains(old.getRelationshipNeighbor(newOld.Data)) && list.Contains(current.getRelationshipNeighbor(prevOfCurr.Data)))
                    || old.getRelationshipNeighbor(newOld.Data).Equals(current.getRelationshipNeighbor(prevOfCurr.Data)))
                {
                    a1 = old.Data;
                    b1 = newOld.Data;
                    a2 = current.Data;
                    b2 = prevOfCurr.Data;
                    r1 = old.getRelationshipNeighbor(newOld.Data);
                    r2 = current.getRelationshipNeighbor (prevOfCurr.Data);
                    found = true;
                }
            }

            //If there is a blank relationship, no analogy may be made.
            if (r1.Equals("") || r2.Equals(""))
                return "";
            //if a1 equals a2 and b1 equals b2, no analogy may be made.
            if (a1.Equals(a2) && b1.Equals(b2))
                return "";
            //If the relationship is directional and b1 does NOT equal b2, then
            //no analogy may be made.
            if (directional && !(b1.Equals(b2)))
            {
                return "";
            }//end if

            //if (old.getRelationshipNeighbor(newOld.Data).Equals(prevOfCurr.getRelationshipNeighbor(current.Data)) &&
            //	old.getRelationshipNeighbor(newOld.Data) != "" && prevOfCurr.getRelationshipNeighbor(current.Data) != "")
            //{
            //string relationship = old.getRelationshipNeighbor(newOld.Data);

            // enable bilingual mode

            string a1_en = a1;
            string a1_cn = a1;
            if (a1.Contains("##"))
            {
                a1_en = a1.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                a1_cn = a1.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            string b1_en = b1;
            string b1_cn = b1;
            if (b1.Contains("##"))
            {
                b1_en = b1.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                b1_cn = b1.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            string r1_en = r1;
            string r1_cn = r1;
            if (r1.Contains("##"))
            {
                r1_en = r1.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                r1_cn = r1.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            string a2_en = a2;
            string a2_cn = a2;
            if (a2.Contains("##"))
            {
                a2_en = a2.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                a2_cn = a2.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            string b2_en = b2;
            string b2_cn = b2;
            if (b2.Contains("##"))
            {
                b2_en = b2.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                b2_cn = b2.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            string r2_en = r2;
            string r2_cn = r2;
            if (r2.Contains("##"))
            {
                r2_en = r2.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                r2_cn = r2.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            // 4 nodes
            sentencePatterns.Add("[Just as " + a1_en + " " + r1_en + " " + b1_en
                + ", so too " + a2_en + " " + r2_en + " " + b2_en + ".] " + "##"
                + "[正像" + a1_cn + r1_cn + b1_cn + "一样," + a2_cn + r2_cn + b2_cn + "。] " + "##");

            sentencePatterns.Add("[" + a2_en + " " + r2_en + " " + b2_en
                + ", much like " + a1_en + " " + r1_en + " " + b1_en + ".] " + "##"
                + "[" + a2_cn + r2_cn + b2_cn + "," + "就像" + a1_cn + r1_cn + b1_cn + "。] " + "##");

            sentencePatterns.Add("[Like " + a1_en + " " + r1_en + " " + b1_en + ", "
                + a2_en + " also " + r2_en + " " + b2_en + ".] " + "##"
                + "[像" + a1_cn + r1_cn + b1_cn + "一样," + a2_cn + "也" + r2_cn + b2_cn + "。] " + "##");

            sentencePatterns.Add("[The same way that " + a1_en + " " + r1_en + " " + b1_en
                + ", " + a2_en + " " + r2_en + " " + b2_en + ".] " + "##"
                + "[如同" + a1_cn + r1_cn + b1_cn + "一般," + a2_cn + r2_cn + b2_cn + "。] " + "##");

            sentencePatterns.Add("[Remember how " + a1_en + " " + r1_en + " " + b1_en
                + "? Well, in the same way, " + a2_en + " also " + r2_en + " " + b2_en + ".] " + "##"
                + "[就像" + a1_cn + r1_cn + b1_cn + "一样," + a2_cn + "也" + r2_cn + b2_cn + "。] " + "##");

            sentencePatterns.Add("[" + a2_en + " also " + r2_en + " " + b2_en
                + ", similar to how " + a1_en + " " + r1_en + " " + b1_en + ".] " + "##"
                + "[" + a2_cn + r2_cn + b2_cn + "," + "正像" + a1_cn + r1_cn + b1_cn + "。] " + "##");

            int random_int = rnd.Next(sentencePatterns.Count);

            return_message += sentencePatterns[random_int];
            //}

            //DEBUG
            Console.WriteLine("return_message: " + return_message);

            return return_message;
        }
        //optional parameter for_additional_info, if set true, will avoid any actual leading statements
        //except for relationship mentions. If no relationship mention can be made, then blank string
        //is returned.
        private string LeadingTopic(Feature last, Feature first, bool for_additional_info = false)
        {
            string return_message = "";

            string first_data_en = first.Data;
            string first_data_cn = first.Data;
            if (first.Data.Contains("##"))
            {
                first_data_en = first.Data.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                first_data_cn = first.Data.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            Console.WriteLine("In LeadingTopic, first_data_en " + first_data_en + " first_data_cn " + first_data_cn);

            string last_data_en = last.Data;
            string last_data_cn = last.Data;
            if (last.Data.Contains("##"))
            {
                last_data_en = last.Data.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                last_data_cn = last.Data.Split(new string[] { "##" }, StringSplitOptions.None)[1];
            }

            Console.WriteLine("In LeadingTopic, last_data_en " + last_data_en + " last_data_cn " + last_data_cn);

            //First is the current node (the one that has just been traversed to)
            //A set of possible lead-in statements.
            List<string> lead_in_statements = new List<string>();
            lead_in_statements.Add("{There's also " + first_data_en + ".} " + "##" + "{还有" + first_data_cn + "呢。} " + "##");
            lead_in_statements.Add("{But let's talk about " + first_data_en + ".} " + "##" + "{我们来聊聊" + first_data_cn + "吧。} " + "##");
            lead_in_statements.Add("{And have I mentioned " + first_data_en + "?} " + "##" + "{之前我说过" + first_data_cn + "吗?} " + "##");
            lead_in_statements.Add("{Now, about " + first_data_en + ".} " + "##" + "{接下来是" + first_data_cn + "。} " + "##");
            lead_in_statements.Add("{Now, let's talk about " + first_data_en + ".} " + "##" + "{接着我们说说" + first_data_cn + "吧。} " + "##");
            lead_in_statements.Add("{I should touch on " + first_data_en + ".} " + "##" + "{我要谈谈关于" + first_data_cn + "。} " + "##");
            lead_in_statements.Add("{Have you heard of " + first_data_en + "?} " + "##" + "{你听说过" + first_data_cn + "吗?} " + "##");

            //A set of lead-in statements for non-novel nodes
            List<string> non_novel_lead_in_statements = new List<string>();
            non_novel_lead_in_statements.Add("{There's also " + first_data_en + ".} " + "##" + "{还有" + first_data_cn + "呢。} " + "##");
            non_novel_lead_in_statements.Add("{Let's talk about " + first_data_en + ".} " + "##" + "{我们谈谈" + first_data_cn + "吧。} " + "##");
            non_novel_lead_in_statements.Add("{I'll mention " + first_data_en + " real quick.} " + "##" + "{我想简要提提" + first_data_cn + "。} " + "##");
            non_novel_lead_in_statements.Add("{So, about " + first_data_en + ".} " + "##" + "{那么,说说" + first_data_cn + "。} " + "##");
            non_novel_lead_in_statements.Add("{Now then, about " + first_data_en + ".} " + "##" + "{现在谈谈" + first_data_cn + "吧。} " + "##");
            non_novel_lead_in_statements.Add("{Let's talk about " + first_data_en + " for a moment.} " + "##" + "{我们聊一会儿" + first_data_cn + " 吧。} " + "##");
            non_novel_lead_in_statements.Add("{Have I mentioned " + first_data_en + "?} " + "##" + "{之前我说过" + first_data_cn + "吗?} " + "##");
            non_novel_lead_in_statements.Add("{Now, about " + first_data_en + ".} " + "##" + "{接着是" + first_data_cn + "。} " + "##");
            non_novel_lead_in_statements.Add("{Now, let's talk about " + first_data_en + ".} " + "##" + "{现在我们谈谈" + first_data_cn + "吧。} " + "##");
            non_novel_lead_in_statements.Add("{I should touch on " + first_data_en + ".} " + "##" + "{我要说说" + first_data_cn + "。} " + "##");

            //A set of lead-in statements for novel nodes
            //TODO: Author these again; things like let's talk about something different now.
            List<string> novel_lead_in_statements = new List<string>();
            novel_lead_in_statements.Add("{Let's talk about something different. " + "##" + "{我们聊点别的吧。" + "##");
            novel_lead_in_statements.Add("{Let's talk about something else. " + "##" + "{我们说点其他的吧。" + "##");
            novel_lead_in_statements.Add("{Let's switch gears. " + "##" + "{我们换个话题吧。" + "##");

            Random rand = new Random();

            // Check if there is a relationship between two nodes
            if (last.getNeighbor(first.Data) != null || first.getNeighbor(last.Data) != null)
            {
                string relationship_neighbor_en = last.getRelationshipNeighbor(first.Data);
                string relationship_neighbor_cn = last.getRelationshipNeighbor(first.Data);
                string relationship_parent_en = last.getRelationshipParent(first.Data);
                string relationship_parent_cn = last.getRelationshipParent(first.Data);

                Console.WriteLine("In LeadingTopic, relationship_neighbor_en " + relationship_neighbor_en + " relationship_neighbor_cn " + relationship_neighbor_cn);

                if (relationship_neighbor_en.Contains("##"))
                {
                    relationship_neighbor_en = relationship_neighbor_en.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                    relationship_neighbor_cn = relationship_neighbor_cn.Split(new string[] { "##" }, StringSplitOptions.None)[1];
                }
                if (relationship_parent_en.Contains("##"))
                {
                    relationship_parent_en = relationship_parent_en.Split(new string[] { "##" }, StringSplitOptions.None)[0];
                    relationship_parent_cn = relationship_parent_cn.Split(new string[] { "##" }, StringSplitOptions.None)[1];
                }//end if

                // Check if last has first as its neighbor
                if (!last.getRelationshipNeighbor (first.Data).Equals("")
                    && !(last.getRelationshipNeighbor (first.Data) == null))
                {
                    return_message = "{" + last_data_en + " " + relationship_neighbor_en + " "
                        + first_data_en + ".} " + "##" + "{" + last_data_cn + " " + relationship_neighbor_cn + " "
                        + first_data_cn + ".} " + "##";
                    return return_message;
                }//end if
                // If last is a child node of first (first is a parent of last)
                else if (!last.getRelationshipParent (first.Data).Equals("")
                            && !(last.getRelationshipParent(first.Data) == null))
                {
                    return_message = "{" + last_data_en + " " + relationship_parent_en + " "
                        + first_data_en + ".} " + "##" + "{" + last_data_cn + " " + relationship_parent_cn + " "
                        + first_data_cn + ".} " + "##";
                    return return_message;
                }//end else if
            }//end if
            // Neither neighbor or parent/child.
            //If this is for additional info, return blank string; the two nodes
            //are not neighbors or have a blank relationship.
            if (for_additional_info)
                return "";

            // NEED TO consider novelty value (low)
            //else if (last.getNeighbor(first.Data) == null || first.getNeighbor(last.Data) == null)

            //If the novelty is high enough, always include a novel topic lead-in statement.
            if (noveltyValue >= 0.6)
                return_message += novel_lead_in_statements[rand.Next(novel_lead_in_statements.Count)];
            //Otherwise, include a non-novel topic lead-in statement.
            else
            {
                return_message += non_novel_lead_in_statements[rand.Next(non_novel_lead_in_statements.Count)];
            }//end if

            //!FindSpeak(first).Contains<string>(first.Data)

            return return_message;
        }