Hello Vikas,
in HANA native modelling there is nothing which can be 1:1 compared to BW transformations. I think behind that there is a good reason: Avoid bad performance imperative logic which slows down the execution of models.
But there are some constructs which can be used to enrich your models with more sophisticated logic. Beside the power of projection, join, union and aggregation nodes you have also the options to enrich your models using Calculated Columns and Restricted Columns. For "more complex" data sources you can also use Table User Defined Functions.
Regarding your described required I think it is possible (w/o knowing the details what you wanna reach) to achive it using two projections with corresponding filters for Date open/Date closed.
In general I think it is a good approach to make you familiar with the HANA modeling capabilities described in the Modeling Developer Guides (Introduction to Modeling - SAP HANA Modeling Guide - SAP Library or for XS Advanced (if you are already using it) Introduction to Modeling in the SAP HANA Web IDE - SAP Library).
Regards,
Florian