Why Middleware Matters Arnold Rots Jonathan Mc Dowell

Why Middleware Matters Arnold Rots Jonathan Mc. Dowell

Why Look under the Hood? • The VO is intended to be user-friendly and we shouldn’t bother users with technical trivia • It’s good to be aware that there needs to be something under the hood which requires resources • For the more sophisticated user having some idea of what is under the hood helps in taking full advantage of the VO

Data Model • If different client applications and different data repositories want to be able to communicate with each other, they need to have a common understanding of what it is they are talking about – A concept of the subject matter – Exchange sufficient information – Unambiguous (consistent) information – Use a common vocabulary

Metadata • This means that (under the hood) there need to be explicit and precise standards on the metadata that are exchanged • And an infrastructure of middleware tools to handle these

Space and Time Metadata • Need to be explicit and precise – Near field / far field: • Your galaxy cluster image may be of interest to solar system research: state where you were when you took the picture – Time: • For precision timing it matters whether you use UTC or TT, and where your reference point is – Doppler velocities • Just because you do, don’t assume everybody else defines Doppler velocity using LSR and radio def.

Spectral Energy Distributions • SEDs are extremely important – and extremely tricky • Try combining radio flux densities, IR & optical magnitudes, X-ray fluxes, Γ-ray photons into a coherent and consistent spectrum • It requires specific knowledge in terms of metadata, conversions, and algorithms

We Need this Stuff • The VO does not want to bore you with the ins and outs of what’s under the hood • And you don’t need to know much about it • But you do need to be aware that ease of use requires an infrastructure • If it is crucial for you to know what can and cannot be done, the information is available