One of the main hurdles towards a wide endorsement of ontologies is the high cost of constructing them. Reuse of existing ontologies offers a much cheaper alternative than building new ones from scratch, yet tools to support such reuse are still in their infancy. However, more ontologies are becoming available on the web, and online libraries for storing and indexing ontologies are increasing in number and demand. Search engines have also started to appear, to facilitate search and retrieval of online ontologies. This paper presents a fresh view on constructing ontologies automatically, by identifying, ranking, and merging fragments of online ontologies. Categories and Subject Descriptors I.2.4 [Knowledge Representation Formalisms and Methods]: Representation languages, Semantic networks; H.3.3 [Information Search and Retrieval]: Search process, Selection process Keywords Automatic ontology construction, ontology reuse, ontology segmentation, ontology merging, ontology ranking