Explain the main differences between the database and IR systems mentioned in Table 27.1.

Table 27.1

Table 27.1 A Comparison of Databases and IR Systems Databases IR Systems 1 Structured data Unstructured data Schema driven I Relational (or object, hierarchical, and network) model is predominant Structured query model Rich metadata operations Query returns data Results are based on exact matching (always correct) No fixed schema; various data models (e.g., vector space model) Free-form query models I Rich data operations - Search request returns list or pointers to documents I Results are based on approximate matching and measures of effectiveness (may be imprecise and ranked)