
we analyse the intuitive concept of reflectivity which directs
our definition of an abstract notion of sequential deterministic reflective al-
gorithms in Sect. 4.3. As characteristic examples for the practice of reflective
programming we specify the reflective behaviour of programs in three con-
crete (logical, functional and imperative) languages: Prolog (Section 4.4),
LISP (Section 4.5), and the reflective version RASP (Random Access Stored
Program Machine) of the RAM (Section 4.6). In Sect. 4.6.1 we show an ex-
ample of a reflective machine at work, namely a RASP simulation of indirect
addressing. The simplicity and the expressive power of our generic concept of
reflective machines are also highlighted by using reflectivity to define a com-
putationally universal abstract machine (Sect. 9.1.2.1, pg. 228). In Sect. 4.7
we compare the reflectivity features of the mentioned languages with our def-
inition of reflective ASMs and relate them with the closely related concept
of reification of programming features, a different reflectivity style offered for
example by Java.

### The Architecture
When operating on structured objects one might wish to permit the inde-
pendent specification of two or more ‘local’ updates in parts of the structure
that are then combined (‘aggregated’) into one ‘global’ update of the struc-
ture, possibly also mediating conflicts that could occur among the given local
updates. This consideration applies in full generality to multiple so-called
partial updates for any structured objects, like sets, functions, graphs, trees,
programs, and also to multiple assignments to shared locations in concurrent
runs, e.g. a counter where updates by different agents may be intended to be
applied cumulatively

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