# Introduction
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In this section we present a brief summary of portfolio theory in a **multi-period time setting**, which constitutes the backbone of the SmartFolio analytical framework. Multi-period time setting implies that an investor is allowed to rebalance his/her portfolio continuously. Its single-period counterpart was developed by Harry M. Markowitz in his celebrated Modern Portfolio Theory. As opposed to multi-period settings, the single-period investment model stops the investor from rebalancing his/her portfolio during its lifespan. In other words, any portfolio strategy under a single-period setting retains a constant number of units in each asset until the investment horizon has been reached.
While the maths behind the continuous-time portfolio theory is far more complicated, its logic stays mostly the same. Fortunately, the essential properties of efficient portfolios under single-period and multi-period settings appear to be much similar, which makes it possible to use results obtained in the single-period model in its multi-period counterpart. In particular, in the simplest case scenario, the structure of respective optimal portfolio strategies is shifted from a constant number of units in each asset to constant **portfolio weights**.
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