Public art is not a single art form. Instead, the concept of public art system is multi-functional, multi-layered, multi-angled and multi-formational. In a city, all urban public facilities other than architecture can become an element of the public art system by means of artistic development and creation.[4] As a result, public art can be achieved in many different ways, such as through sculptures, murals, drawings, photography, body of water, park facilities, landscape, street lights, urban furniture and structure; it can also be urban public facilities of landscape art, installation art, visual art, high-technology art, light art, performance art, performing arts and so on. (See Figure 1) Elements of public art in the circulatory system of urban construction[5] form an intact system of public art, which forms the holistic features of the city together with the architectural system. The meaning of public art lies not in its form, but in the value it embodies. As Sun suggests, public art is not an art form or a unified school or style. Rather, it is a way of thought that allows art in the public space to develop a relation with society’s public in the contemporary cultural context. It is a spirit and attitude that demonstrates democracy, openness, exchange and sharing in the public space.[6] In the process of the urban construction of public art, the public’s involvement is always emphasized. The artists together with the public complete the public artwork’s presentational form. The public’s involvement makes public art really an art of the public. The result of the public’s involvement in public art is achieving the artwork’s interaction, meaning the mutual exchange and influence between the artist and the public. The subjects in the interaction are parallel. The interaction is the extension of the artwork. It leads to the result of the public art’s openness. The real meaning and humanistic value of an artwork can only be achieved through interaction.

　　Wenzhi Zhang Sculpture Garden View

　　2. The Wholeness of Public Art

　　Architecture and public facilities other than it form the unity of the city. Public facilities other than architecture can become elements of the public art system through artistic development and creation. Therefore, the scope of urban public art is very wide and it includes a variety of elements.

　　This essay applies the characteristics of general system theory (wholeness, relativity, dynamics, sequency, teleology) (See Figure 2) as suggested by Ludwig Von Bertalanffy[7] in the realm of public art in order to carry out a systematic study. System theory has it that every thing can be looked at as a system, and a system includes different elements that are interrelated; they interact and influence each other, and affect the function of the whole system. System theory emphasizes on the unity of a system, through which it deduces the operational patterns. By considering the system’s unity and overall situation, it improves the system’s structure and function.[8] This essay uses the characteristics of general system theory as an approach to study the public art system in the circulatory system of urban construction. It systematizes the complex, broad and diverse urban public art construction by identifying the organizations and patterns, and provides the frame and structure for the study of public art system theory. By adopting the characteristics of general system theory in the study of the public art realm, this essay provides the basic patterns of the structural theory as a basis for the study of public art system theory.

　　Fig 2 The characteristics of Bertalanffy’s general system theory　　

　　The elements of the public art system in the circulatory system of urban construction, which includes sculptures, murals, architectural ornaments and garden design, do not exist independently, but are instead, interdependent, interrelated and bear mutual influence. They co-exist in different space of the city. The features of public art and the city’s overall environment are closely linked. Taking the mentioned elements of the public art system as examples: sculptures are artworks built within the city’s space; murals are artworks attaching on the surface of architecture; gardens are often designed to serve as the city’s “lung”. The unorganized elements in the public art system can still form a unity together, but without organization they cannot become a system. The unity of a system must lie in the unity of a certain organizational structure.[9] The elements must be interrelated and interact in a way that forms a certain systematic structure in order to attain systematic unity.

　　The sculptures existing in the urban public space seem to be unorganized but are in fact interrelated and they interact with each other. It is an important manifestation of the unity of the urban public art system. As Bertalanffy’s discourse on wholeness in his General System Theory describes, generally speaking, the overall organization of physics, such as atoms, molecules and crystals, originated from the association of pre-existing elements. On the contrary, the overall organization of organisms is gradually built from the differentiation of the primeval unity.[10] Therefore, if we use the organic system as a metaphor for a city[11], then the functional organs in the human body would be metaphors for the different public art forms in the urban public art system; these functional organs are the essential and inseparable components of the overall system.

　　Consequently, every construction of the urban public art is closely related to the overall urban environment. Any construction of a city’s public art element must be included into the overall management system of the urban circulatory system.

　　Fig 3 The overall relations in the circulatory system of urban construction　　

　　3. The Relativity of Public Art

　　The interrelations between elements that complete the urban public art system are examined in light of the principle of relativity of systems theory.[12] The ecological environment,[13] artificial environment,[14] humanistic environment[15] and spiritual Fig 3 The overall relations in the circulatory system of urban construction

　　environment are the objectively existing elements that put together public art within the circulatory system of urban construction.(See Figure 3) Bertalanffy suggests that “a system can be defined as a complex of interacting elements,” and the whole is composed through their interrelations.[16] If a city is analogous to a biological mechanism, functions of various organs of the mechanism are interrelated. If a system is a set of component elements, the elements of various organs of the mechanism thus establish a biological system.

　　For instance, thousands of public art pieces displayed in the public space on both sides of Chicago’s Michigan Avenue and a few hundred thousand public art works at the heart of Manhattan illustrate the relations between elements of public art within the system and how their interactions assists in establishing a city's urban morphology. If, in any case, these public art works fail to compose the foundation of the whole, they will then cease to be the elements of the system. The rhythm of the system is manifested through the interrelations of elements.

　　A city is synonymous with an organism. While an organism is constantly regulated by metabolism, the growth of public art in a city is similar to the metabolic activities in a body.[17] When the public art system in the circulatory system of urban construction is examined against the long history of urban planning and development, we can unravel the changes, occurred over the course of time, in the aesthetics and criterion of city public art. Given the inevitability of urban development, the dynamics of public art is bound to evolve with time and culture.

　　4. The Dynamics of Public Art