Arabic is a collection of dialectal variants that are historically related but significantly different. These differences can be
seen across regions, countries, and even cities in the same countries. Previous work on Arabic Dialect identification has
focused mainly on specific dialect levels (region, country, province, or city) using level-specific resources; and different efforts
used different schemas and labels. In this paper, we present the first effort aiming at defining a standard unified three-level
hierarchical schema (region-country-city) for dialectal Arabic classification. We map 29 different data sets to this unified
schema, and use the common mapping to facilitate aggregating these data sets. We test the value of such aggregation by
building language models and using them in dialect identification. We make our label mapping code and aggregated language
models publicly available.