Since 2011, schema.org has been introduced by search engines such as Bing, Google, Yahoo! and Yandex to become a de facto standard for semantically annotating data, content, and services on the web. Schema.org focuses on defining types and properties to describe “things” on web pages that are most valuable to automated agents (e.g. search engines, chatbots or personal assistant systems). This implies that search engines and dialog assistants get the information they need most to improve search results and give the required answer.

Schema.org is designed for annotating any relevant content on the World Wide Web. In conclusion it provides a rather large vocabulary not specific to a certain domain. Vice versa, for a given domain schema.org may only provide a very superficial coverage. Domain Specifications ([Şimşek et al., 2017], [Panasiuk et al., 2018a], and [Panasiuk et al., 2018b]) are a means to deal with these two challenges. First, it allows to restrict the overall complexity of schema.org need to cover given domains and tasks. Second, it provides a structures approach to extend schema.org for domain and task specific needs.

References:

[Panasiuk et al., 2018a] Panasiuk, O., Kärle, E., Simsek, U., and Fensel, D.: Defining Tourism Domains for Semantic Annotation of Web Content. In e-Review of Tourism Research (eRTR), Research Notes in ENTER 2018 Conference, Vol. 9, 2018.
[Panasiuk et al., 2018b] Panasiuk, O., Akbar, Z., Gerrier, T. and Fensel, D.: Representing GeoData for Tourism with Schema.org. In Proceedings of the International Conference on Geographical Information Systems Theory, Applications and Management, 17-19 March, 2018.
[Şimşek et al., 2017] Şimşek, U., Kärle, E., Holzknecht, O., and Fensel, D.: Domain specific semantic validation of schema.org annotations. In International Andrei Ershov Memorial Conference on Perspectives of System Informatics, pp. 417-429, Springer, Cham, 2017.