Fischer von Erlach's reconstruction of Split, from his Entwuerff einer historischen Architektur, Vienna 1721, Tafel X
Although the site is traditionally called the Palace of Diocletian, and has monuments in a setting suitable for the enactment of imperial ceremonies, there is no universal agreement that - for example - the peristyle was so used, or indeed that Diocletian after his retirement was due for or received any cermonial attention.
The whole question is confused by our limited knowledge of just how ceremonial functioned at this time. The current state of play seems to be that the pro-palace lobby (Dyggve 1941, L'Orange 1965) has lost to the pro-villa lobby (Duval 1965, Wilkes 1986), who point to the achronicity of referring to ceremonial from the Byzantine court (i.e. several centuries later) and trying to fit it to a setup of about 300 AD. The "villa lobby" also point out that the format of Diocletian's Palace - that is, a walled country residence - is to be found in subsequent North African villas (known from mosaics): Diocletian's villa at Spalato was thus not an isolated phenomenon. If one makes allowance for the obvious differences of scale and elaboration, it can be seen to reflect the same current of events as that which produced a whole series of fortified villas, quasi-military in plan, which began to emerge on the provincial scene during the closing years of the third century (Boethius & Ward-Perkins 1970, 527).
Here is just such a villa, seen in a 3rd century mosaic from Carthage, and now in the Bardo Museum, Tunis:
The basic design as regards the airy piano nobile colonnade we find at Split on the sea front has been a feature of Roman villas probably since the late Republic, as seen in the view of a Campanian seaside villa from a house at Pompeii (destroyed 79 AD):
Thus the villa of Piazza Armerina in Sicily (cool as a parallel, now that few accept it as an Imperial villa, let alone as the retirement villa of Diocletian's companion-Emperor, Maximian), is of approximately the same date, and also has "interestingly" shaped rooms. Better still, the recently excavated villa at Gamzigrad in eastern Serbia, has been identified as the villa-residence of the Emperor Galerius, who took over as Augustus from Diocletian. What is more, it has palace-like structures inside (Wilkes 1986, 66ff. for a description).
Another very likely source is the palace which Diocletian as Emperor built for himself at Antioch, known to us only through a description by his contemporary Libanius:
The whole of it is an exact plan, and an unbroken wall surrounds it like a crown. From four arches which are joined to each other in the form of a rectangle, four pairs of stoas proceed ... towards each quarter of the heaven. Three of these pairs running as far as the wall, are joined to its circuit, while the fourth is shorter but is the more beautiful ... since it runs toward the palace, which begins hard by, and serves as an approach to it... (quoted from Boethius & Ward-Perkins 1970, 527).
Split has the same stoas, or covered colonnades, the same focus on the palace, and the spectacular crossing point of the four colonnades, forming a similar design to Antioch's tetrapylon.
The source of the Palace of Diocletian in the Roman military camp is quite clear - as clear as the Hellenistic and then Roman tradition of colonnaded streets, and Wilkes (1986, 60) sees the military significance of Peristyle, porch and vestibule is intelligible as a provision for military ceremony implied by the arrangement in contemporary forts. Certainly, comparisons can be made with the layout at sites such as Timgad, where the Via Principalis and the Via Praetoria adopt a similar plan (Boethius & Ward-Perkins 1970, 526).
This is fine as far as it goes - but what military ceremonial is associated with a retired Emperor? And is it known definitively that Diocletian took no part in Imperial (or ex-Imperial) ceremonial?
It is at this point that the potential flexibility of XMosaic should come into play! What we need is experts in the field attaching arguments, sketch plans, excavation reports and good old-fashioned deadly-polite polemic to this document. After all, one of the aims of networking any document should be that they change and grow - dynamic electronic discussion documents (rather than the old sequential ones) which take advantages of the possibilities inherent in multimedia.
From here you may go to any of the following pages:
The Introductory Page; The Colonnaded Streets; Comparisons with Split's Architecture; Diocletian as Builder; The Emperor's Apartments; The Great Hall & Peristyle Complex; The Emperor's Mausoleum; The Temple; The Walls & Gates A short description of the Tetrarchy; The Bibliography; My Biography; The technology I've used; A Short Research Paper.