Open data is receiving considerable attention because of its potential for public and private sector innovation. Various governments have the policy of providing data sets to the public via open data portals. Data sets are published in a format defined by a source, which makes it difficult to discover a useful data set and requires user interpretation of structure and semantics. Meta data insertion and semantic annotation address these problems, but are not yet widely implemented for open data. Also privacy issues and commercial sensitivity have to be addressed, leading to (technical) interventions like access restrictions and billing functions. Users might also want to be informed only of data changes with publish/subscribe functions to increase the quality of decisions based on large data sets. Data transformation, billing, security, monitoring, and publish/subscribe functionality has to be associated with data sets that are available via Application Programming Interfaces. Application Programming Interface management platforms providing this type of functionality are central to implementing open data. This paper analyses required functionality for data sharing considering the above mentioned requirements and matches these requirements with functionality of available platforms.