links

Hilltop constructs a query-specific authority graph by restricting link-based scoring to "expert documents" - non-affiliated pages containing topically relevant outbound links - thereby isolating genuine editorial endorsement from self-serving or incidental citation networks. Standard PageRank-style algorithms fail to distinguish between links reflecting deliberate expert judgment and links reflecting co-location, reciprocity, or structural spam, producing authority scores that reward link acquisition rather than topical relevance. This implies that ranking durability depends on source qualification upstream of link weighting: a page's authority signal degrades predictably when the underlying linker set lacks demonstrable topical expertise, making expert-filtered link graphs structurally resistant to manipulation at scale.

TrustRank is a semi-automatic spam-fighting framework that propagates trust scores from a small, manually curated seed set of high-quality pages through the hyperlink graph to assign legitimacy scores to all crawled documents. The system exploits the observation that good pages rarely link to spam, enabling trust to decay with link distance from seeds while isolating link-spam clusters that accumulate inbound links without receiving trust propagation. Search engines applying TrustRank can suppress or demote low-trust pages during ranking, reduce crawler resources wasted on spam-dense host neighbourhoods, and prioritise indexing of nodes with non-trivial trust scores - effectively making large-scale link manipulation economically unviable without proximity to authoritative seed pages.