Semantic modeling language (SMDL) report models are deprecated. Although you can you continue to use existing report models as data sources in SQL Server 2012 Reporting Services reports you should consider updating your reports to remove their dependency on report models.
SQL Server 2012 Reporting Services does not include tools for creating or updating report models.
SQL Server Data Tools (SSDT) no longer supports report model projects. The Report Model designer is not available in SQL Server 2012 Reporting Services (SSRS). You cannot create new Report Model projects or open existing projects in SQL Server Data Tools (SSDT) and you cannot create or update report models. To update report models, you can use SQL Server 2008 R2 Reporting Services or earlier tools. You can continue to use report models as data sources in reports authored in SQL Server 2012 Reporting Services (SSRS) tools such as Report Builder and Report Designer. The query designer that you use to create queries to extract report data from report models continues to be available in SQL Server 2012 Reporting Services.
Sources: here and (mainly) here
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