The advances in hardware and software have been rapidly integrated by organizations, especially in the healthcare sector, demanding new approaches for software to provide more reliable products, under well-known quality standards. This thesis investigates, designs and implements a set of operationally crucial RESTful web services for Invian Oy ERP system, DomaCare. Today, DomaCare is one of the fastest growing and developing software solutions in Finland in the healthcare sector. Thousands of satisfied healthcare professionals across Finland use DomaCare daily. DomaCare is a versatile ERP system designed specifically for the social sectors. This thesis describes the theoretical part of software architecture and software architectural style, which support understanding REST. Second, the thesis introduces the environment and tools required for the development stage. Third, the thesis presents the action and sequence diagrams for each use case to support the overall understanding of the system in a higher level of abstraction. Moreover, unit tests were implemented in this thesis for each use case, and, finally, the approach which was employed to validate the system is presented. In conclusion, the thesis concludes that based on the literature review, implementation, the results obtained from the unit tests, and the system validation fulfilled the goals set for this thesis.Tiivistelmä. Laitteistojen ja ohjelmistojen tekniikkaa on nopeasti integroitu organisaatioihin erityisesti terveydenhoitoalalla. Tämä vaatii ohjelmistojen osalta uudenlaisia lähestymistapoja, jotta jatkossa voidaan tarjota luotettavampia ja tunnettujen laatustandardien mukaisia tuotteita. Tässä diplomityössä esittelen tutkimusvaihetta, suunnitteluprosessia sekä toteutustapoja toiminnallisesti tärkeän, REST-arkkitehtuurimallia noudattavan webrajapinnan toteuttamiseksi Invian Oy:n DomaCare-toiminnanohjausjärjestelmässä. Tänä päivänä DomaCare on yksi Suomen terveydenhuoltoalan nopeimmin kasvavi