Describe and evaluate the working memory model

Proposed by Baddeley and Hitch in the 1970s following a series of dual-task experiments, the working memory model (or the multi-store model) comprises 4 slave systems: the central executive, the phonological loop (auditory information), the visuo-spatial sketchpad, and the episodic buffer (transferring information from the central executive to long term memory). This model was developed to explain how we store limited amounts of information with minimal processing, as well as the reason why we cannot do certain tasks - ones that require the use of the same slave system - simultaneously.
This model does well to explain parallel processing, unlike Attkinson and Shiffrin's memory model. It portrays memory as an active process rather than a passive one. Support for it comes from ... [insert one of the experiments].
However, these experiments fail to explain the function of the central executive or to prove its existence. Furthermore, ecological validity is limited in the aforementioned studies as they were highly controlled laboratory experiments. In real life there may be a lot more distracting factors interfering with the working memory functioning, which were not taken into account in these experiments. [insert a study which was less controlled?]