There are three levels that need to be addressed in this regard:
The motivation and will to integrate (organizational level)
Standard definitions (language level)
Standard for electronic storage and exchange (technical level)
The first level is less of a topic in this guide, which takes as a point of departure that a decision has been taken about integration of data. However, it is an important issue and usually the most complex to solve given the range of actors involved in the health sector. Clear national policies on data integration, data ownership, routines for data collection, processing, and sharing, should be in place to address this issue. Often some period of disturbance to the normal data flow will take place during integration, so for many the long-term prospects of a more efficient system will have to be judged against the short-term disturbance. Integration is thus often a step-wise process, where measures need to be taken for this to happen as smoothly as possible.
At the language level, there is a need to be consistent about definitions. If you have two data sources for the same data, they need to be comparable. For example, if you collect malaria data from both standard clinics and from hospitals, this data need to describe the same thing if they need to be combined for totals and indicators. If a hospital is reporting malaria cases by sex but not age group, and other clinics are reporting by age group but not sex, this data cannot be analyzed according to either of these dimensions, though a total amount of cases will be possible to calculate. There is thus a need to agree on uniform definitions.
In addition to uniform definitions across the various sub-systems, data exchange standards must be adopted if data is to be shared electronically. The various software applications would need this to be able to understand each other. DHIS2 is supporting several data formats for import and export, but one standard format now supported by WHO is called SDMX-HD (Statistical Data and Metadata Exchange - Health Domain). Other software applications are also supporting this, and it allows the sharing of data definitions and aggregate data between them. For DHIS2, this means it supports import of aggregate data that are supplied by other applications, such as OpenMRS (for patient management), iHRIS (for human resources management)