If you are someone who was exposed to the world of reporting through Ax reports then there is a dilemma that you would face when you create a Ax-SSRS report for the first time. The dilemma is the perception towards data methods.
Conceptually Ax data methods and SSRS data methods are quite different, this has to do with their architecture.
When MS planned it’s migration from SSRS to Ax reports, the major reason cited was the randomness or the chaotic way of data gathering and rendering from Ax.
The Ax reporting engine does preparation of data and rendering of the same in an alternative way. A record is fetched and then all the additional information related to it is processed (display methods) and then it is rendered. This means every record fetched is processed before it’s rendered. This is the reason to receive the current record as a parameter for a display method and do calculations on it. This can be too simple but would be cumbersome to scale the reporting ability.
While SSRS reports have a well defined approach here. The data that is to be displayed in the reports are processed first before rendering. So even calculated/display methods are pre-processed and the data is kept ready. This data is then passed to the rendering engine which renders it. This is a more structured and scalable approach to follow.
When I had to start with SSRS for the first time It took me sometime to figure out this. Thanks to Saveen and the Dynamics BI team for making it much easier to understand for everyone. Today there is loads of SSRS Demo available in the Youtube Dynamics Ax BI Channel including the one that details about data method.
Data method related videos
Watch out to tune in your reports perception