Drawing Annotated Parse Tree for Syntax Directed Definition Im trying to draw an annotated parse tree for 3*5+4n, the text book shows the following:


[Compilers - Principles, techniques and tools (Dragon Book) by Aho, p308]

I have a few questions regarding this


Why is 3*5+4 considered as a single string? Can't I draw a parse tree something like 
for the same string ie:with operator at the node  
What is the need for giving T.VAL=3 and then giving another child F.VAL=3. (I understand that the integer attribute for digit needs to be supplied by the lexical analyzer)
The Dragon book style starts with the parse tree of the expression, i.e., the root (I think the very top is a mistake, the expression is an error as written) is the step $E \Rightarrow E + T$. The tree is then decorated giving the attributes their value (like $E.val = 19$). In an attributed grammar you give the grammar and the attributes, so that the grammar looks in part as (subindices mark diferent uses of the same symbol, left to right):
\begin{eqnarray}
E \rightarrow T \quad E.val \leftarrow T.val \\
E \rightarrow E + T \quad E_0.val \leftarrow E_1.val + T.val
\end{eqnarray}
You see that the answer to your second question is that the value of the child $F$ is used to compute the value of $T$.