The core of SlapOS is the SLAP protocol. SLAP stands for “Simple Language for Accounting and Provisionning”. With SLAP, every computer part of a Cloud publishes on so-called SlapOS Master the list resources which are available to others then receives from SlapOS Master resources to allocate and notifies to SlapOS Master resource usage for a given period of time. Thanks to SLAP, IaaS, PaaS and SaaS are unified together with metering, accounting and billing.
SLAP is implemented in SlapOS by SLAPGRID, the accounting and provisionning runtime of the Compatible ONE R&D project. Developers can use SLAP either through the SLAP API or by implementing the SLAP Procol.
The SLAP API mainly consists of the request() method. Python and Java libraries are provided to developers. PHP, Javascript, Ruby and Perl libraries are considered.
The SLAP protocol exists in two form: XML-RPC and REST. The SLAP payload can either be XML or JSON. XML-RPC is the easiest for integration to existing web sites, since it mimics HTML form data and requires practically no coding. REST is the modern way to use the SLAP protocol with a documentary approach. The choice of XML vs. JSON is mostly a question of taste. XML provides more mature tools for data validation in most environments while JSON is preferred for its lighter syntax in other environments.