Introduction¶

DAS is an opensource virtual data service integration platform. The acronym DAS stands for Data Aggregation System. It provides a a common layer above various data services, allowing end users to query one (or more) of them with a more natural, search-engine-like interface. It is being developed for the [CMS] High Energy Physics experiment on the [LHC], at CERN, Geneva, Switzerland. Although it is currently only used at the CMS experiment, it was designed to have a general-purpose architecture which would be applicable to other domains.

It provides several features:

1. a caching layer for underlying data-services
2. a common meta-data look up tool for these services
3. an aggregation layer for that meta-data

The main advantage of DAS is a uniform meta-data representation and consequent ability to perform look-ups via free text-based queries. The DAS internal data-format is JSON. All meta-data queried and stored by DAS are converted into this format, according to a mapping between the notation used by each data service and a set of common keys used by DAS.