
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given an ellipse C: $$\frac {x^{2}}{a^{2}}+ \frac {y^{2}}{b^{2}}=1(a＞b＞0)$$ with a focal length of $$2 \sqrt {3}$$, and C passes through the point $$( \sqrt {3}， \frac {1}{2})$$.
(I) Find the equation of ellipse C;
(II) Let B₁, B₂ be the lower and upper vertices of ellipse C, respectively. P is any point on the ellipse other than B₁ and B₂. Draw a line PM perpendicular to the y-axis at M, and N is the midpoint of line segment PM. Line B₂N intersects with the line y = -1 at point D. E is the midpoint of line segment B₁D. O is the coordinate origin. Determine whether $$\overset{ -}{ON}\cdot \overset{ -}{EN}$$ is a constant value. If it is, find the value; if not, explain the reason.

Present the answer in LaTex format: \boxed{Your answer}
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