Update Knowledg Graph Representation (RDF and Property Graph) and Schema.md

Author: heathersherry

topics/Knowledg Graph Representation (RDF and Property Graph) and Schema.md

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 ## Knowledg Graph Representation (RDF and Property Graph) and Schema
 
-### RDF
-1. 
+### RDF 
+__General Papers__
+1. Relational schema optimization for RDF-based knowledge graphs (Information Systems 2021) [[Paper](https://www.sciencedirect.com/science/article/pii/S0306437921000223)] 
+
+__Queries and Search over RDF based KG__
+1. Faceted search over RDF-based knowledge graphs (Journal of Web Semantics 2016) [[Paper](https://www.sciencedirect.com/science/article/pii/S1570826815001432)] 
+2. Semantic SPARQL similarity search over RDF knowledge graphs (VLDB 2016) [[Paper](https://dl.acm.org/doi/pdf/10.14778/2983200.2983201)] 🌟
 
 ### Property Graph
-1. Property Graph Schema Optimization for Domain-Specific Knowledge Graphs [[Paper](https://arxiv.org/pdf/2003.11580.pdf)] (ICDE 2021) 🌟
+1. Property Graph Schema Optimization for Domain-Specific Knowledge Graphs (ICDE 2021) [[Paper](https://arxiv.org/pdf/2003.11580.pdf)] 🌟