With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Silicon Valley refers to the southern part of the San Francisco Bay Area in California.
text_B: In cartography , a phase line is a line to show some positional dependency or relation to the passage of time , most often changing phases of a military operation , or changing borders in histogeographic maps .. cartography. cartography
not_related.