I am using Protegè to model a human drug domain: molecules, medicines, producers, related codes, etc.
Would there be some easier form of GUI in which I could draw classes, object and data properties graphically as nodes, edges and labels?
Protégé is a free and open source ontology editor. However, there are many other alternatives to Protégé to develop an ontology. These are mentioned below.
The PoolParty Semantic Suite based on the SKOS (Simple Knowledge Organization System), ontologies, and Linked Data principles, is an enterprises knowledge management system that uses standards-based technologies as defined by W3C. It transforms data into RDF graph that can be queried using SPARQL query language.
The KAON (Karlsruhe ontology) is an ontology infrastructure offering reasoning support for OWL ontologies.
The NeOn Toolkit which is based on the Eclipse platform is an open source, multi-platform ontology editor, which supports the development of ontologies in F-Logic and OWL/RDF. It provides ontology engineering activities such as Annotation and Documentation, Modularization and Customization, Reuse, Ontology Evolution, Translation, etc.
OntoUML which is built as an UML extension is based on the Unified Foundational Ontology (UFO) and is an ontologically well-founded language for Ontology-driven Conceptual Modeling.