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Both sides previous revision Previous revision 2014/10/12 15:04 popel 2014/10/12 15:03 popel 2013/03/27 16:56 vandemos 2013/03/22 14:54 popel 2013/03/19 00:05 popel 2013/03/18 20:27 vandemos vytvořeno Go Next revision		Previous revision 2014/10/12 15:04 popel 2014/10/12 15:03 popel 2013/03/27 16:56 vandemos 2013/03/22 14:54 popel 2013/03/19 00:05 popel 2013/03/18 20:27 vandemos vytvořeno Go
courses:rg:2013:memm [2013/03/19 00:05] popel		courses:rg:2013:memm [2014/10/12 15:04] (current) popel
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-	===== Maximum Entropy Markov Models =====	+	===== Maximum Entropy Markov Models - Questions =====
-	**1.** Explain (roughly) how the new formula for α_t+1(s) is derived (i.e. formula 1 in the paper).	+	1. Explain (roughly) how the new formula for α_t+1(s) is derived (i.e. formula 1 in the paper).
-	**2.** Section 2.1 states "we will split P(s|s',o) into |S| separately trained transition functions". What are the advantages and disadvantages of this approach?	+	2. Section 2.1 states "we will split P(s|s',o) into |S| separately trained transition functions". What are the advantages and disadvantages of this approach?
-	**3.** Let S= {V,N} (verb and non-verb)	+	3. Let S= {V,N} (verb and non-verb)
	Training data = he/N can/V can/V a/N can/N		Training data = he/N can/V can/V a/N can/N
	//Observation features// are:		//Observation features// are:
Line 13:		Line 13:
	When implementing MEMM you need to define s_0, i.e. the previous state before the first token. It may be a special NULL, but for simplicity let’s define it as N.		When implementing MEMM you need to define s_0, i.e. the previous state before the first token. It may be a special NULL, but for simplicity let’s define it as N.
	a) What are the states (s) and observations (o) for this training data?		a) What are the states (s) and observations (o) for this training data?
-	b) Equation (2) defines features f_a based on //observation features// b. How many such features do we have?	+
		+	b) Equation (2) defines features f_a based on //observation features// b. How many such f_a features do we have?
	c) Equation (3) defines constraints. How many such constraints do we have?		c) Equation (3) defines constraints. How many such constraints do we have?
		+
	d) List all the constraints involving feature b2, i.e. substitute (whenever possible) concrete numbers into Equation (3).		d) List all the constraints involving feature b2, i.e. substitute (whenever possible) concrete numbers into Equation (3).
		+
	e) In step 3 of the GIS algorithm you need to compute <latex>P_{s’}^{(j)}(s|o)</latex>. Compute <latex>P_N^{(0)}(N|can)</latex> and <latex>P_N^{(0)}(V|can)</latex>.		e) In step 3 of the GIS algorithm you need to compute <latex>P_{s’}^{(j)}(s|o)</latex>. Compute <latex>P_N^{(0)}(N|can)</latex> and <latex>P_N^{(0)}(V|can)</latex>.

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