Sentence 1: The thick walls still clearly outline the fort's boundaries.

Sentence 2: The fort does not have perimeter walls.
Is this second sentence entailed by the first?

Answer: no

Sentence 1: it's no big deal

Sentence 2: I didn't mind doing this.
Is this second sentence entailed by the first?

Answer: it is not possible to tell

Sentence 1: Until the early 1990s much of the coastline was undeveloped, but a rash of building projects creates an almost continuous ribbon all along the shoreline.

Sentence 2: There wasn't much development before 1990.
Is this second sentence entailed by the first?

Answer:
yes