  Many geoportals such as ArcGIS Online are established with the goal of
improving geospatial data reusability and achieving intelligent knowledge
discovery. However, according to previous research, most of the existing
geoportals adopt Lucene-based techniques to achieve their core search
functionality, which has a limited ability to capture the user's search
intentions. To better understand a user's search intention, query expansion can
be used to enrich the user's query by adding semantically similar terms. In the
context of geoportals and geographic information retrieval, we advocate the
idea of semantically enriching a user's query from both geospatial and thematic
perspectives. In the geospatial aspect, we propose to enrich a query by using
both place partonomy and distance decay. In terms of the thematic aspect,
concept expansion and embedding-based document similarity are used to infer the
implicit information hidden in a user's query. This semantic query expansion 1
2 G. Mai et al. framework is implemented as a semantically-enriched search
engine using ArcGIS Online as a case study. A benchmark dataset is constructed
to evaluate the proposed framework. Our evaluation results show that the
proposed semantic query expansion framework is very effective in capturing a
user's search intention and significantly outperforms a well-established
baseline-Lucene's practical scoring function-with more than 3.0 increments in
DCG@K (K=3,5,10).
