Business-IT alignment (BITA) remains a challenging topic for enterprise architects, and especially operational BITA that focus on the alignment between business processes and IT applications. A major challenge is determining the level of alignment between these Business and IT layers. Some approaches propose to assess this alignment, but they are often context-specific. Moreover, no approach intends to combine various assessment means for a more in-depth alignment evaluation. Thus, we propose an alignment assessment approach combining different means (metrics, consistency rules, anti-patterns). We also provide a methodology that integrates this approach by relying on an established cartography expressing the current state of alignment. This cartography is composed of Business and IT models, and of explicit links between them. The proposed methodology and assessment approach are illustrated on the SoftSlate case study, an open-source Java E-commerce solution. In the reported experiment, we considered four metrics, two consistency rules, and four anti-patterns.