quiz 1 solution

2018-komp-ling/quizzes/quiz-01-response.md

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+# Quiz 1 solution
+
+
+## 1. Which problems does maxmatch suffer from? (Choose all that apply.)
+
+a) requires comprehensive dictionary
+
+d) constructs non-grammatical sentences
+
+On the performance: MaxMatch looks to be slow (*O(len(sentence) + sum(len(entry) for entry in vocabulary))*) on the worst case, but it's hard to construct such case and to meet such example in the natural language text.
+
+---
+## 2. Write a perl/sed substitution with regular expressions that adds whitespace for segmentation around "/" in "either/or" expressions but not around fractions "1/2":
+
+```
+sed 's/\([^0-9]\+\)\/\([^0-9]\+\)/\1 \/ \2/g'
+```
+
+---
+## 3. the text mentions several times that machine learning techniques produce better segmentation than rule-based systems; what are some downsides of machine learning techniques compared to rule-based?
+
+Machine-learning techniques are often harder to interpret (e.g. all these NN-based solutions). Having found the group of mistakes produced by the ML-algorithm you won't just add a bugfix cause the whole model needs to be rebuilt and retrained.
+
+---
+## 4. write a sentence (in English or in Russian) which maxmatch segments incorrectly.
+
+An ambigous example from the school textbook: "наполеонсеялрожь". Maxmatch will choose the less statistically probable examle "наполеон сеял рожь".
+
+---
+## 5. what are problems for sentence segmentation? provide one example in English or Russian for each that applies.
+Depends on the segmentation algorithm. 
+### a) ambiguous abbrevations with punctuation
+
+"... и т.п. случаи."
+
+### b) sentences containing symbols '!' and '?'
+
+"Are you O.K.?!"
+
+"Here ```!condition ? do_this_if_inverted_condition_is_true : do_that_if_inverted_condition_is_false``` is the ternary operator usage example."
+
+### c) sentences lacking separating punctuation
+
+>Hello, this is my first email
+>
+>And i will not use dots to finish last sentences in the paragraph. And I also love WYSIWYG
+>
+>Yours, me.
+
+### d) sentences not separated by whitespace
+
+"The first sentence.The second one."