General Comments:

In a number of instances there are words called out in italics - "informal urbanization was perceived as a cancer" -suggesting that someone said this but you're not telling us who. Either site a source or use your own description and eliminate the italics.

Urbanisms of the Informal:
Transformations in the Urban Fringe of Mexico City

To make the experience of conflict a maturing one requires the destruction of an assumption regnant since the work of Haussman; that the planning of cities should be directed to bring order and clarity to the city as a whole.  Instead the city must be conceived as a social order of parts without a coherent controllable whole form.  This disorder is better than dead predetermined planning.
 
Richard Sennet, The Uses of Disorder

The phenomenon of informal urbanization has become the single most pervasive element in the production of cities in developing countries.  The magnitude of this modality of city-making has rendered it as the norm rather than an exception in the growth of developing world cities as  something natural to the urban environment rather than an aberration.  The terms ‘favelas’, ‘barriadas’, ‘kampongs’, ‘slums’, ‘villas miserias’, ‘bidonvilles,’ or ‘asentamientos irregulares’ are only local manifestations of a globalized phenomenon.  The Informal has eroded our notion of what a city is and has seriously challenged the purpose (would ‘efficacy’ be better?) of urban planning altogether.  Mexico City  represents the paradigm of such an urban condition: an area of 1,400 square kilometers containsa population of 20 million inhabitants approximatetly 60% of whom live in settlements that began through some mode of informal urbanization. (Connolly 1982; Ward 1998). Peter Hall called Mexico City the “ultimate world city: ultimate in size, ultimate in population, ultimate in threat of paralysis and disintegration, ultimate in the problems it presentsÖ”(Hall 1984, p89)  

These ultimate situation prompts an alternative reading of Mexico City through the glass of informal urbanization.  The object is threefold: First, I will argue that the rise of informal urbanization and its entry into the professional design realms during the late 1950’s and 60’s coincides, both synchronically, and in terms of ideas, with some of the dominant critiques of modern city planning.  Second, I will describe why and how informality has become the dominant mode of production of urbanity in Mexico City and how the evolution of the two most significant  informal settlements in the urban fringe of Mexico City explicate or illustrate this process inthe developing city.    Finally, I hope to sketch the relevance of this phenomenon to the disciplines of architecture and urban planning by presenting a new term, Urbanisms of the Informal, and describe some of its strategies that can serve to engage, in a more instrumental way, both the forms and the procedures of this urban condition.

On the rise of informal urbanization
Informal urbanization is conventionally regarded as development that takes place outside the legal, planned, and regulated channels of city-making. Usually it is characterized by indiscriminate occupation of land, lack of official approval, lack of property titles, makeshift housing, and absence of utilities and human services. (Cymet 1992, p3).
The notion of informality is contingent to the existence of norms. In other words, informality enters our consciousness only at the moment that the State decides to normalize practices once considered marginal  (Tomas and Azuela 1997, p234).  It was only after the origins of modern city planning in the mid nineteenth century that the existence of zoning and codes makes informality a relevant phenomenon.  This conception clearly sets informal urbanism  apart from other urban productions such as the medieval town or other forms of vernacular that share similar  traits with the phenomenon of informal urbanization, yet   are nevertheless different in their forms and procedures.
While present sporadically throughout history, informality becomes an important phenomenon only after the mid Twentieth century.  The fact that it coincides with other important critiques of CIAM urbanism and other forms of modern city planning might be enlightening. (vague--how? this is interesting, but needs to be better explained)
The boom of informality in developing countries in the early 1960s? coincides with a series of significant challenges to the assumptions of modern architecture and urban planning; dominant discourses, both European and North American, were opening to urban conditions in other parts of the world.
At the forefront of this challenge were the activities and projects of Team X, the Metabolists, the Situationists and also individuals as diverse as Henry Lefevbre, Christopher Alexander, Jane Jacobs and Melvin Webber.
Team X developed a fascination with regionalism, the vernacular, the spontaneous, the open-ended, the “self-organizing”, – subjects suppressed by modernism– which  became central to their productions.  These fascinations took different guises by different members of the group.  Aldo van Eyck took an interest in the Dogon culture of Sub-saharan Africa, as well as in other forms of primitive dwelling like Pueblo architecture. His interest in the order of these urban phenomena was not that of the classical/modern tradition, but rather in the responses of human behavior to accommodate (accommodate what? or do you mean adapt to?) within the constraints of architecture.  His studies provided a critiqueof the modern movement’s goal to eliminate slums and substitute them with worst conditions in living.
Allison and Peter Smithson’s notions of “human association” “ordinariness” and “urban restructuring” also point to a less ‘heroic’and more quotidian approach to urban planning.  In a different way, Candilis and Wood’s work with ATBAT in Northern Africa was more instrumentally informed by the aesthetics of traditional settlements, than by the procedures.
From Giancarlo de Carlo’s work in Urbino and his later obsession with user participation, to Christopher Alexander, who devoted much of his life to developing participatory methods of designing, we find in this fascination with the “vernacular” or the spontaneous a recognition of the absence of the architect as a value in the built environment.
Worth noting as well, are Fumihiko Maki’s Investigations in Collective Form and Melvin Webber’s notions of "social processes operating in space", "spatially structured processes," and "form in action" (Webber 1964, p 89).
This interest in the human-architectural symbiosis and in the self-organizing processes is evidence of a lack of faith in the traditional methods of modern architecture to engage in the transformation of everyday life and in resolving the problems of present-day society.  I believe that in this light, we can understand the change in attitude towards the urban condition of informality.

(I appreciate all of the examples that you have given in the above paragraphs, and it does serve to further your argument, but they are treated so superficially that they almost seem like name dropping. It is very frustrating. I think it would help enormously to explain much more fullly the work of the Smithsons and van Eyck, and maybe Giancarol de Carlo and how specifically their projects relate to a new form of urbanism, and maybe mention then simply that Maki, Webber, and others were doing similar research.)

Some of the earliest references to the phenomenon of informal urbanization appear in the work of John F.C. Turner and Charles Abrams (Abrams 1964; Turner 1968)(Abrams 1966).  Turner, an English architect educated at the Architectural Association in London during the 1950’s was  influenced by anarchist writers like first name Kropotkin, (who were also in London? or who were teaching at the AA? what is the relevance of this connection?).  (why did he go to Peru? like “The possibility of studying the urban ramifications of an anarchistic government led him to ?”Peru to work in community development programs and learned firsthand the experience of the barriadas in Lima.  Prior to the 1960’s, informal urbanization was perceived as a ‘cancer’ and locus of subversive groups which remained outside the experience of modernity.
Turner’s discovered the -(word choice?) of informal settlements and promoted their acceptance as a legitimate solution to the problem of housing and urbanization in the developing world. (This must be must more specific. what did he discover?  what were the virtues?  In his writings, most notably Housing by People and Freedom to Build, Turner criticized finished (modern? or government built?) housing as a very limited way of dealing with the real problems of housing. (on what basis?) Turner instead found that when thedwellers controlled  major decisions and were free to make contributions in design, construction, or management of their housing, the environment produced, stimulated individual and social well-being.  Turner’s ideas wereinfluential in developing countries and agencies such as the World Bank. (how?) what does this have to do with the world bank He would ultimately work as an advisor to housing agencies in Mexico and other developing countries and his theories would become the standard for housing policies all over the globe. 

Turner’s success in identifying the phenomenon of informal urbanization and its related social structure resulted in a important number of theoretical works and projects during the 1970’s  These works focused predominantly  on developing countries and remained  mostly marginal from dominant discourses of architecture and urban planning.  Paradoxically the more important informality became that of the urban landscape Architects became less involved with informal development  and during the 1970’s and 80’s, the interest in this  urban conditionshifted from the disciplines of architecture and urban planning to those of sociology, anthropology and political economy. 

Urban legends: Four misconceptions of informal urbanization
When discussing informal urbanization, a number of prevailing myths and misconceptions need to be debunked.  These misconceptions exist amongst the general polulace, but amazingly persist among design and planning professionals.  To challenge these myths is to clarify thecondition and open up the possibility of engaging it in more productive ways.
Misconception #1.	Informal urbanization is unplanned urbanism
Informal urbanization involves a series of decisions, strategies and policies that, if minimal or unorthodox, amount to a form of planning. Squatting and 'spontaneous' invasions represent only a small percentage of the overall processes of informal urbanization.  The assumption that informal urbanization is unplanned or irrational ignores the sophisticated and sometimes more effective devices that individualsemploy to allocate resources, organize space and resolve social and economic needs.  This form of planning is foremost  a spatial practice where decisions and strategies develop alongside the transformations of physical and social space. 
Misconception #2.	Informal urbanization is only self-built housing
While still practiced, self-built housing is not the dominant modality of informal urbanization.  To assume that the production of housing is the only component of informal urbanization is to neglect the myriad strategies and forms that configure this type of urbanity.  Informality also includes the construction of public space and infrastructure. The tendency to equate urbanization with housing establishes a false polarity between the self-builder and the building industry  (the state, developers, landowners, and contractors), which in turn ignores the complex dynamics of this form of urbanization.
Misconception #3.	Informal urbanization will ultimately disappear
With every structural, political or economic change (industrialization, internal migration, modernization, population growth rate reduction), there has been a 'promise' that informal urbanization will disappear.  The common perception that the problem of informal housing can be resolved through regulated housing programs fails to recognize both the history of urban fringe development, and the rationalchoices settlers make everyday in their housing decisions. In light of the State’s limitations in providing housing and the minimum share of housing market that formal developers provide, the economic access of the poor to standard housing remains extremely hindered.
Misconception #4.	Informal urbanization is not a legitimate form of urbanity 
Citizens, politicians and even urban specialists still fail to regard informal urbanization as a serious and valid mode of development.  However itslegitimacy should not be understood only as a legal operation; itsvalidity is based on much more than just Lefevbre’s “Right to the City”.  Aside from the power and magnitude of the phenomenon, informal urbanization has generated a series of mutations and creative surges (word choice--mutations and creative surges?) in the practices of architecture and planning..  Evidence of this legitimacy is in the fact that rather than the informal city disappearing, Mexico City, has become Informal.

500 years of informality in the Valley of Mexico
Informality has played a major role In constructing Mexico City’s urban space for centuries.  Most of Tenochtitlan, the ancient Aztec capital, was built in defiance of official rules and practices (Hardoy and Satterthwaite 1989, p25).  Ignacio Castera’s plan of colonial Mexico City, drawn over 200 years ago sketched the city’s  future ensanche and included an informal city outside the plannedregulated colonial grid.  Even during the mid 18th century when the first subdivisions of land were created by private developers, irregularity was manifest in the way the land was sold and occupied, and in the lack ofpublic services provided by developers.  Informality in the 20th century did not arise spontaneously as many people seem to believe but rather, followed the same pattern of practices and mechanisms taking place for centuries.. (Varley 1989a).  The city of palaces, as Alexander von Humboldt called Mexico City, in 19??was also the city of the Informal.  However, in the last  50 years the architecture and city planning in Mexico City have increasingly  intertwined with the phenomenon of informality.

In 1949, Mario Pani finished the multifamily housing project President Miguel Aleman.  A ‘unite de hatitation’ in its own right, the Multifamiliar Juarez represented a highpoints of Mexico’s architectural, social, and political modernity .  Paradoxically, at precisely the same time Pani built his unite, informality was becoming the dominant modality of city-making in the city’s periphery.  During the next 25 years, architects and planners engaged in an ultimately lost battle with the problem of housing a growing population, and understanding the urbanization dynamics of a megalopolis that exceeded  their conceptual tools and frameworks.

Two settlements are paradigmatic of Mexico City’s informal urbanization in the last 50 years.  Athough they were developed at different times and in different ways, Neza and Valle de Chalco nevertheless share a scale, magnitude and relevance to the broader megalopolis.

I would like to see more specific description of the spatial  characteristics of both Neza and Chalco. These sections form the backbone of  the piece and both are very readable and interesting, but I am left wondering exactly what these places are like architecturally.  As a concluding sentence to the section on Neza you state that 'a high degre of social interaction, plurality and spatial complexities' make it a mature and sophisticated city in its own right. I don't disagree, but I'd like to get a sense of what that spatial complexity and plurality is. You mention that Neza is comprised principally of 2-3 story single family dwellings - are they made of concrete block? Recycled materials? Do most of the buildings look the same? How many houses 'deep' until the next street? Does Neza have a different architectural characted than Chalco?  Are there streets or squares that form the centers of the community? In the section on Chalco you mention that the grid is 'far less flexible, making the relationship betwen street frontage and lot area inefficient.' I'd like to know more about what constitutes the street frontage, how it's different than Neza, how it's inefficient.

Neza: The Anti-Atlantis
Neza, short for Ciudad Nezahualcoyotl is an area of roughly 3,800 hectares, twelve kilometerskm east of downtown Mexico City, located in the region formerly occupied by Texcoco Lake. Its development is intimately related to the drainage operations of Texcoco Lake in the Mexico City Valley that were begun by the  Spanish colonists in the 1600s?and continued into this century.  Neza initially developed during the mid 1940s on land with dubious legal tenure. The receding water line of the lake continually reconfigured the territory generating property disputes that remained unresolved for decades.

If one of the ideal cities in the western tradition has been Atlantis, the mythical city buried under waters, then Neza is its anti-thesis; a city that was exposed asthe waters of Lake Texcoco receded in mid 20th century. Neza counters the utopian ideals of Atlantis, -civilization, form, community and city-, with the short term tactics of flexibility, informality pragmatism and action. (in this last sentence you are opposing community , city and civilization with flexibility, etc. , undermining your argument--that community, city and civilization can arise from informality,pragmatism, no? I very much like the idea, but what ideals of atlantis are opposite than neza--heirarchical planning? form? I don’t know atlantis well enough, to say ,but you should.The name Neza, even today, evokes exaggerations, images of chaos, injustice, fraud, despair, vulnerability, crime and real estate speculation. Both in public opinion, as well as professional circles, Neza became the symbol of everything that was wrong with the city, plagued by pollution, environmental decay and uncontrolled. Critics (more specifically who?)called Neza a bastard urbanization, a cancer that should have never been allowed to grow.(should you site these quotes?)  The development of Neza coincided with Mexico City entering a permanent state of crisis. (specifically what do you mean by a permanent state of crisis?)

Two dominant events precipitated the founding of Neza. Rural migration created significant demographic changes Mexicoin the mid twentieth century.   Almost 60% of Neza’s population in 1970 were born elsewhere in the country. This rapid growth in Mexico City’s population sparked a series of disjointed urban policies implemented by the local governments of the Federal District (DF) and the State of Mexico. Rent control policies implemented in downtown Mexico Citycombined with uncoordinated governmental regulations that banned land subdivisions and limited growth forced masses of residentsto move t to the periphery to find housing..  Neza, with its privileged location just over the state line, was an obvious first choice.
The drainage of Texcoco lake and the immediate pattern of land sales and appropriations point to a rational, almost Jeffersonian  subdivision of land. The first operation(implemented by who?) to define the urban pattern used a gridiron at two scales: a maxi-grid – 1km by 1km- that organized the territory in districts, and, a mini-grid, which arranged each district according to its own distinct logic.  The district typologies varied according to the different developers and to the mode of occupation; invasion or illegal sale.  A typical district consists of orthogonal blocks 150 x 40 meters and is de?limited by avenues 45 meters wide (one and a half times wider than Avenues in Manhattan).  Most districts originally contained a large central site for public facilities and open space Over time, most of these squares have been infilled leaving the districts with minimal public space.  Individual private lots are roughly 150 square meters.
 Neza developed both through illegal land subdivisions and sales by developers and through invasions by squatters.  The illegal subdivisions resulted from owners holding dubious property titles or from  developers defaulting on the provision of services. The question remains why such a vast development, if illegal was allowed to be built. Contrary to the belief that clandestine developers started all settlements, the people and the companies involved in the development of Neza never hid their activities. Drawings and plans were widely usedfor sales and marketing, and in some cases, they revealed an elaborate comprehension of urban plansThese plans were  probably  created by other developers working within the primary land market at the same time.  These plans show street hierarchies as well as areas for schools, markets, medical facilities and open space. Areas developed through squatting reveal minor irregularities in the standard, orderly grids and some realignment of streets.
The first land sales took place in 1946, and continued strong for 25 years without governmental  provision of services or infrastructure. Settlers and buyers organized into social and civic groups to deal with tasks such as the provision of water through tank trucks, obtaining health and education facilities, and minimizing damage from flooding.  Urbanity (what is urbanity? governmental support for the development?) was progressively achieved (when-date?)through negotiation with developers and State authorities.
 In the late 1960’s a variety of these civic groups organized into the Movimiento Restaurador de Colonos (MRC) (Movement for the Restoration of Settlers) Settlers fought against both fraudulent developers who were not fulfilling promises to provide services and infrastructure, and the State that was not heeding to their needs.  By channeling demands and articulating protest, the MRC was able to achieve many of the improvements that currently exist in Neza.  During the early 1970’s the MRC organized a payment boycott,vandalized developers' offices numerous times resulting in  a number of violent clashes between local police and settlers. The MRC as most other popular grassroots movements, was ultimatetly  co-opted by the city government.  Initially weakened by a schism in the movement in 1971, the establishment of FINEZA in 1973 eliminated the MRC. FINEZA was fiduciary fund created by the government in 1973, as a response to increasing protests over the urban, political, administrative and judicial problems of Neza. Although dismantled, the MRC not only set a precedent for other grassroots movements striving for urbanity, but also served as  a model for the provision of urban services in most informal urbanization.  The MRC was, in a way the first group of 'bottom-up' planners in Mexico.
After 1973, Neza moved into the realm of formal planning and the State’s efforts turned to focus on granting clear and legal land deeds, and to organizing  urban services.  A parallel history of architecture and planning decisions continued to be taken at the level of individuals and organized groups, from the progressive construction of the individual private dwelling, to the construction and appropriation of public space.
Neza was transflormed from a  desolate territory, to a city of almost 1.5 million people in less than fourty  years. The current population densityof 363 inhabitants per hectare represents an astonishing number considering that, the primary land use is two to three story single family dwellings. Neza has become a fulllymatured city with a high degree of social interaction, plurality and spatial complexities that other ‘planned’ communities can only desire.

Valle de Chalco: The territory of informality
Valle de Chalco covers an area of roughly 2,200 hectares located in the southeastern fringe of metropolitan Mexico City, thirty kilometers from the center of the city.  Similar to Neza, the settlement is located on a former lakebed, Lake Chalco.  From the early twentiety century to the late 1960s Lake Chalco was drained for high-yielding agriculture.  The expansion of industry into the valley ultimately polluted the water, making it impossible for farmers to grow productive crops.  By the 1970s Valle de Chalco was a bleak valley with high pastures, an active floodplain during the summer months
Viewed from the air, Valle de Chalco exceeds what is considered urban(whatdoes this mean, exceeds what?) and enters the realm of geography as its vastness achieves a territorial condition.  The same flat, gray, unfinished, homogenized space extends for kilometers.  Only the Xico volcano, the canal bordering Chalco Lake,,the 'diagonals' of the highway, the right of way for high-tension electricity lines, and the railroad line serve as boundaries and references within a large tabula rasa.
At a first glance, Valle de Chalco and Neza  appear similar. Both consist ofa continuous orthogonal grids developed on a former lakebed. However,  on closer examination, they have considerable differences, both in the planning processes undertaken, and in the urbanity thatdeveloped.
Organized land invasions and other forms of squatting were not the norm in Valle de Chalco, rather, it was through widespread illegal sales of the ejido lands in the late 70s that the valley was developed. Clandestine real estate brokers made arrangements with the agricultural communities in order tosell the land with relative ease. Unlike Neza, in Valle de Chalco, there was never an explicit promise or contract from the developers to the settlers regarding planned services such as electricity, water or sewage.  Settlers assumed that infrastructure and services were extras to be demanded by them and provided by the state over a long period of time rather than the developer’s obligations.
The first areas to be occupied in Valle de Chalco were those between the highway and the sewage canal to the north. (do we have a map? other wise the description of north is meaningless) The highway served as a development corridor because it provided access to transportation and jobs in the factories nearby. (I assume the reason you meniton the sewrage canal is because it provided another appropriated infrastructure..) After this initial development, settlement continued to spread without clear resulting in dispersed growth over a large region rather than concentrated growth in smaller areas.
From 1978 to 1984 illegal sales proliferated, but in 1984 municipal authorities clamped down on the developers, taking some of them to prison.  Paradoxically, sales remained consistent, withcollisions between ejidatarios and local authorities abounding throughout the 1980’s. A strong connection emerged between the developers, local authorities and  official political party, making it a commonplace for illegal practices to be approved or tacitly allowed by public servants. (Legorreta 1994, p 118).
 	Unlike Neza, Chalco never had a district nor an overall city-wide plan.  Real Estate operations were carried out with plans drawn on a piece of cardboard or drawn on the ground in situ  The apparent regularity of the urban pattern can be attributed to the fact that ejido properties followed a orderly gridiron and that some developers involved in subdividing Chalco had previous experience in Neza. 
The absence of public and semi-public space in Valle de Chalco is brutal.  Urbanization has been reduced to its minimum, and the block’s patterns rarely escape the tight-knit scale associated with single-family housing. In some cases the limited provision of space for public amenities was a product of negotiations between ejidatarios/developers and settlers but in most cases, settlers simply 'appropriated' empty land to preserve it for schools and markets.  Unlike an orthodox division of public and private spaces, the street has become the site for public life, from the open-air market to playground, as an extension of the private space. 
Valle de Chalco is comprised of around 25 different districts.  Although they vary in size, each district contains on average over 3,000 lots, close to 200 city blocks. The standard lot is around 190 square meters but over 25% of the dwellings have only one room. In the early 1990s the average dwelling was fourty-one square meters and over half of the dwellings were less than thirty square meters. (Hiernaux Nicolas and LindÛn Villoria 1997). An average of 5.41 persons live in each dwelling,the highest densities in Valle de Chalco are close to 200 persons per hectare.

In the late 1980s and early 1990s, Valle de Chalco became the center of national attention.  President Salinas instituted a poverty alleviation program, PRONASOL, which he tested in Valle de Chalco. PRONASOL provided funds for specific projects but requiredthe community’s participation in the project through time and work thuschanging traditional paternalistic processes of providing services.  Iin a matter of months the conditions of urban space in Valle de Chalco were changed. 
PRONASOL provided electricity for all Valle de Chalco in just 60 days.  Before the provision of the 'legal' electricity, the system of illegal connections known as the 'telaraÒa' (cobweb)had provided irregular access to light.  Water provision was another success of PRONASOL.  In the early years of the settlement, residents obtained water through hydrants along the highway, from illegal wells from delivery by water trucks.  After 1995, over 90% of the dwellings had runningwater..

As Chalco was built with far less planning than Neza, its grid is far less flexible making the relationship between street frontage and lot area inefficient.  However Valle de Chalco’s development involved a less problematic relationship between settlers and developers.  If migrations and demographics originated Neza, Valle de Chalco emerged from connection between the informalization of the city and the informalization of economic activities andprocesses which resulted from large economic restructuring.  Valle de Chalco is a territory 'built' through informal practices, but one that nevertheless recreates the conditions of informality and serves as the bastion of an informal economy.

Neza and Valle de Chalco are not isolated phenomena.  Hundreds of settlements in the urban fringe of Mexico City have followed this modality of urbanization in spite, or precisely because of, the intrinsic limitations of formal planning and architecture practices.    Without ignoring their deficiencies they both have developed a distinct and often successful urbanity.  The banal, vulgar, generic and sometimes mediocre qualities of their built environment is never a detraction from the creative transgressions and subversions that take place everyday(we really could use an example of this)  which  challenge our fixed assumptions of what a city is.

Your description of politcal movements is interesting and important, but I also think it's important to keep in mind that we are an architectural journal and to define informal urbanism in those terms as well. I think this could be achieved by the addition of a few sentences specifically describing the physical urban space  in both the Neza and Chalco sections.

       You talk about the fact that public space and infrastructure is part of informal urbanism along with self-built housing - are there examples? I find the statistics regarding population density fascinating, and the  30 square foot dwelling with an average of 5 people is mind blowing.  More information like this that gives us a feel for the characteristics of these places is essential.
  
A new term
The use of specific words and terms to describe new and emerging conditions always runs the risk of sounding trivial or demagogic.  During the 1980s the term informal was used as a semantic blanket to describe anything from self-built dwellings to petty economic activities.  And yet terms such as spontaneous, anarchic, illegal, self-built, or irregular, do not adequatetly describe this urban condition. Conscious of its limitations, I propose the term Urbanisms of the Informal as a possible, if only transitory tool to describe and engage a particular urban condition.  Urbanisms, in plural, not only embraces the complex and heterogeneous forms and procedures that represent this urban phenomenon, but it also engages them both as practice (as in urban planning and design), and as body of knowledge, a new episteme.   The word Informal  is used with its multiple connotations.  Informal means “lacking form”, as in formless, but it also means “outside of the formal, the regular or prescribed”, as in irregular.  Finally, the term informal also refers to “casual” or “ordinary”.

Urbanisms of the Informal refers to the practices (social, economic, architectural and urban), and the forms (physical, spatial) that a group of stakeholders (dwellers, developers, planners, landowners and the state), undertake not only to obtain access to land and housing, but also to satisfy their needs to engage in urban life. These practices are characterized by tactical and incremental decisions, by a complex interaction among players, and a distinct set of spatial strategies that produce a progressive urban space and reconfigured hierarchies.  In using such a definition I strive to separate the association made between terms such as informality and illegality with that of undesirability.  By suspending judgement on the quality of the urban environment produced through informal processes, we can achieve better instrumental understanding of the phenomenon.
If professional attitudes towards this urban condition have traditionally been concerned with how planners and architects can improve informal urbanization, perhaps it is  more relevant to understand how informal urbanization can enlighten the processes and forms we currently use to develop and plan the city.  To do so, we have to understand the spatial strategies of informal urbanization that define its exceptional condition.  With different degrees of complexity, these strategies operate at distinct scales: from the dwelling and the district to the city and the territory.

Shifting hierarchies
In Urbanisms of the Informal the traditional notions of hierarchies of development -of use, of distinction betweenpublic andprivate, and of infrastructure- achieve a high degree of flexibility.  The apparently non-hierarchical space of informalityalways manifest in the use of the grid, in reality configures and reconfigures itself over time.  Shifting hierarchies is the process by which generally accepted spatial hierarchies are substituted with a-posteriori tactics of infrastructure, service provision and land occupation.  As a result, areas of lesser importance early in the development of a settlement eventually take a dominant role, and r areas that had a hierarchy at some point, see their development slowed.
Ecologies of time
Urbanisms of the Informal deal with evolution, over time, in far more complex ways than traditional modalities of urbanization do.  Urbanity is realized by spending more time to consolidate and achieve an 'image of the city'.  It involves a combination of slow and fast strategies that maximize the relationship between stakeholders' resources and needs.  Some residents may build a unitl shell in as little as two weeks while the transition from a shack to finished dwelling may take decades.  This approach to urbanization as a city becoming, shifts our understanding of urbanity as a finished form to urbanity as the density of spatially structured processes.
The human-architectural symbiosis
Theurban configuration of informal urbanization supersedes the mere physical definition of space.  This strategy not only involves high levels of participation by stakeholders in constructing urban space, but also involves a complex intertwining between forms of urbanity and processes that create that urbanity.  From the ad-hoc provision of services and infrastructures such as water and electricity, to the appropriation of a street for an open-air market, the human-architectural symbiosis (unfinished sentence)

To present Urbanisms of the Informal as a way to understand Mexico City, is to inform city- making with a social and political dimension, to relinquish the obsession of control as a desirable tool, and to recognize the limits of form.  It is also a call for a practice of urbanism that is able to embrace the real, the everyday, the generic and the built without prejudices and biases. Rather than Neza or Valle de Chalco looking more like Mexico City, the city will look more like these places.  The future of Mexico City will depend in good part on the ability of planners and architects to acknowledge informality as a constitutive condition of the city and to align frameworks and tools to deal with this evermore complex urban phenomenon.

“ÖBy deletion, combination, deformation, reorganization, we seek to break through the stubborn stereotypes that fortify the city against penetration, and to achieve an effective characterization.  A character thus conveyed is as much made as found.  Capture by rendering is comprehension and creation.  Right and relevant renderings make and remake cities and even remake our way of making cities.”

Nelson Goodman, On Capturing Cities

References:

Abrams, Charles: Man's struggle for shelter in an urbanizing world. Cambridge: MIT Press, 1964.
Abrams, Charles: Housing in the modern world. London: Faber and Faber, 1966.
Connolly, Priscilla. "Uncontrolled settlement and self-build: what kind of solution? The Mexico City case." In Self-help housing: a critique, ed. Peter Ward, 141-74. London: Mansell; Bronx, 1982.
Cymet, David: From ejido to metropolis, another path: an evaluation on ejido property rights and informal land development in Mexico City; American university studies. Series XXI, Regional studies, ISSN 0895 -0482; vol. 6. New York: P. Lang, 1992.
Hardoy, Jorge Enrique, and David Satterthwaite: Squatter citizen: life in the urban Third World. London: Earthscan, 1989.
Hiernaux Nicolas, Daniel, and Alicia LindÛn Villoria. "ProducciÛn del espacio y regularizaciÛn de la tenencia de la tierra en el Valle de Chalco." In El acceso de los pobres al suelo urbano, ed. Francois Tomas and Antonio Azuela. MÈxico DF: PUEC, UNAM, 1997.
Legorreta, Jorge: Efectos ambientales de la expansion de la Ciudad de Mexico, 1970-1993. 1. ed. ed. Col. Del Valle, Mexico: Centro de Ecologia y Desarrollo, 1994.
Turner, John C. "Housing priorities, settlement patterns, and urban development in modernizing countries." AIP Journal, vol. 34 (1968): 354-363.
Turner, John F. C.: Housing by people: towards autonomy in building environments. London: Marion Boyars, 1976.
Turner, John F. C., and Robert joint author Fichter: Freedom to build; dweller control of the housing process, 1972.
Varley, Ann. "Propiedad de la revolucion? Los ejidos en el crecimiento de la Ciudad de Mexico." Revista de la Sociedad Inter Americana de Planificacion, vol. XXII, no. 87-88 (1989a): 125-155.
Webber, Melvin, ed. Explorations into urban structure. Philadelphia: University of Pennsylvania Press, 1964.
Ward, Peter M.: Mexico City. Rev. 2nd ed. ed.; World cities series. Chichester; New York: J. Wiley, 1998.
Hall, Peter Geoffrey: The world cities. 3rd ed. ed. London: Weidenfeld and Nicolson, 1984.