Introduction: In a standards-based school-system alignment of policy documents with standards and assessment is important. To be able to evaluate whether schools and students have reached the standards, the assessment should focus on the standards. Different models and methods can be used for measuring alignment, i.e. the correspondence between standards and assessment. Based on the assumption that a model must be able to include content and cognitive complexity, nine different models are identified and these models are then scrutinized with reference to defined theoretical criteria. The conclusion is that Bloom's revised taxonomy and Porter's taxonomy are the most appropriate models. Method: Bloom's revised taxonomy and Porter's taxonomy are compared based on empirical data from standards and assessment in a chemistry course in upper secondary schools in Sweden. The comparison is based on five rules and of inter-rater reliability. Results: Bloom's revised taxonomy was more inclusive and exclusive than Porter's taxonomy. The inter-rater reliability for classification of standards was significantly better for Bloom's revised taxonomy than for Porter's taxonomy. Conclusion: Based on the five rules, the conclusion is that Bloom's revised taxonomy is the best model. (Contains 3 tables.)