SSI-2021: Scientific Services & Internet

We present a collection of selected materials from the All-Russian Conference "Scientific Services & Internet (SSI-2021), which took place on September 20-23, 2021 at Keldysh Institute of Applied Mathematics in Moscow, Russia. However, because of the worldwide COVID-19 crisis, SSI-2021 had to take place online. The issues discussed at the conference include: digital libraries, information systems, knowledge representation, national bibliographic systems, ontology engineering, parallel computing, Semantic Web, situational modeling. © 2021 Copyright for this paper by its authors.