. just out, includes The Ray Kurzweil Interview,and The Chinese Singularity("Chinese culture has little of the West'ssubliminal resistance to thinking machines or immortal peopleand this cultural difference may manifest itself in the next decadesin subtle ways.")
A brain-controlled bionic hand attached to an amputee's nervous systemvia electrodes implanted into the remaining part of his left armhas been developed by scientists at Pisa's Valdera Polo Sant'Anna School.The patient was able to experience sensations when grasping and making a fist.
European scientists have successfully built a brain-controlled bionic handallowing amputees to feel hand sensationsand manipulate their limb--via the brain--as if it were still there.Pierpaolo Petruzziello--who lost his arm under the elbow in a car crash several years ago--has done just that, Italy's University Campus Bio-Medico of Rome announced Wednesday.The biometric hand was developed atPisa's Valdera Polo Sant'Anna Schooland surgically attached to Petruzziello's nervous systemvia electrodes implanted into the remaining part of his left arm,meaning the robotic body part was actually like an extension of his body.After the surgery at the University Campus Bio-Medico of Rome in November 2008,it took Petruzziello just days to start using the device.During the LifeHand trial, which lasted a month,Petruzziello, 26, was able to experience sensations whengrasping, making a fist, ...The responses from the hand to commands sent from the brain were 95 percent correct,Paolo Maria Rossini, head of neurology for the project, said Wednesday.The next step, which is still at least a couple of years away,is to work out a more long-term experiment that would hopefully lead tocybernetic arms like the LifeHand as a viable option for amputees.The EU has spent $3 million and five years on the project so far,
Making the entire cell using a roll-to-roll processgives the company an advantage over otherthin-film photovoltaic companies that print on glass,which is heavier and limited to smaller areas,says Solexant CEO Damoder Reddy."The cost benefit is dramatic,allowing us to produce cells for 50 cents a watt," he says.First Solar, a thin-film company that uses vacuum depositionto print its cells onto glass,has manufacturing costs of 85 cents per watt.Nanosolar, another company making nanocrystal solar cells,uses a different semiconductor that requires chemical reactionsto take place during printing,which increases the complexity and expense of the process."We print a preformed semiconductor,"which eliminates such steps, says Reddy.The company's first product, which Reddy sayswill sell for $1 per watt next year,will contain a single layer of the nanocrystals.The company is currently developing other types of nanocrystalsthat are more responsive to different bands of the solar spectrumin the hopes of boosting its cells' efficiency."Ultimately we want to make a multilayer, broad-spectrum cell,"says Reddy.. For a truly disruptive project, check out the open-source framework
. a report by an international expert on solar energy. Daniel Nocera describes a long-awaited, inexpensive method for solar energy storagethat could help power homes and plug-in cars in the future
. Scientists have long known how to split water into hydrogen and oxygen,but unlike plants, they've needed high temperatures and harsh solutions,or rare and expensive catalysts like platinum.[without the platinum, the loose hydrogens just stay unbound,increasing the acidity, and complicating containment]Nocera's catalyst is the first made fromcheap, abundant materials (cobalt and phosphate)that works in benign conditions: a glass of water at room temperature.The crucial insight that makes this possible came to Nocera in 2004,when biologists figured out plants' water-splitting machine.They learned that the machine falls apart regularly,requiring the leaf to rebuild it from scratch.They too could let the catalyst break down,then use a small amount of solar energy to reconstruct it, again and again.
a paper describing the work in the July 31 issue of Science."This is just the beginning," said Nocera,principal investigator for the Solar Revolution Projectfunded by the Chesonis Family Foundationand co-Director of the Eni-MIT Solar Frontiers Center."The scientific community is really going to run with this."
Nocera and Matthew Kanan, a postdoctoral fellow in Nocera's lab,When electricity runs through the electrode,the cobalt and phosphate form a thin film on the electrode,and oxygen gas is produced.Combined with another catalyst, such as platinum,that can produce hydrogen gas from water,the system can duplicate the water splitting reactionthat occurs during photosynthesis.The new catalyst works at room temperature, in neutral pH water,and it's easy to set up, Nocera said.Nocera hopes that within 10 years,homeowners will be able to power their homes in daylight through photovoltaic cells,while using excess solar energy to produce hydrogen and oxygento power their own household fuel cell.Electricity-by-wire from a central source could be a thing of the past.This project was funded by the National Science Foundationand by the Chesonis Family Foundation .
. announced a $10 million grantto develop technology to make solar power mainstream.The Chesonis Foundation donated the money for research in three areas:materials to improve conversion of light to electricity;storage;and hydrogen production from solar energy and water.Called the Solar Revolution Project,it will provide funding for 30 five-year fellowships in solar energy.The idea is to pursue "blue sky" research,in an effort to fill the void between corporate-funded applied researchand the limited amount of federal money dedicated to basic science research in solar,said Ernest Moniz, the director of the MIT Energy Initiative."There are some really hard problems that need to be solvedfor the really big breakthroughs to come," Moniz said."The underlying science of photosythesisis extremely complicated and not well understood at the electronic level."As part of the campus-wide MIT Energy Initiative,the university already has other ongoing solar-related research initiatives,including the recently announcedMIT-Fraunhofer Center for Sustainable Energy Systems.The Solar Revolution Project funding is meant to be flexible to allow researchers topursue breakthrough technologies.A solar leadership council will be formed to coordinate activities amongdifferent research efforts at MIT, Moniz said.The Chesonis grant will also help fund asolar energy research report,modeled on the university's influential reports on nuclear and coal.Although the power is free, solar electric panels are relatively expensivebecause of the large up-front cost.Solar power is small fraction of the overall electricity production in the U.S.--just half of one percent in 2007,according to the U.S. Energy Information Administration.. to bring costs down, Researchers and solar companies are trying to developlarge-scale manufacturing technologies and higher solar cell efficiencyThe Chesonis Family Foundation was founded by Arunas Chesonis,an MIT graduate who is CEO of telecom company Paetec Holding.
Even though it is only the size of a postage stamp-- compared to the usual solar collector area that spans 4 x 4 feet --the cell is much more efficient in collecting and reusing solar energy.The lens focuses incoming sunlight onto the solar cell.Microchannels at the base of the moduletransfer energy in the form of heat and light to wires contained inside.Each vertical stack of lenses rolls and tilts like a track blind,keeping the surface of the lenses faced to incoming sunlightas the sun changes position in the sky throughout the day.Incorporating these new cells into arrayscould make solar energy an option that is competitive with other energy sources .
. Boston College researchers have built solar cellsthat get a power boost from the blue light portion of sunlight(whose energy is normally lost in heat).The solar cells could, in theory,result in efficiencies as high as 67 percent of the energy in sunlight,compared to 35 percent with ordinary solar cells...
By the year 2020, you won't need a keyboard and mouse to control your computer,say Intel Corp. researchers,who are close to gaining the ability to build brain sensing technologyinto a headset that culd be used to manipulate a computer,working with associates at Carnegie Mellon University and the University of Pittsburgh.Their next step is development of a tiny, far less cumbersome sensorthat could be implanted inside the brain.
Up to 1000 galaxy clusters have found to bestreaming at up to 1000 kilometers per secondtowards one particular part of the cosmos,a possible sign that other universes are out there....
. If a full cryptographic solution is far-off,what would a near-term solution look like?WD: A practical solution will have several properties.It will require an overall improvement in computer security.Much of this would result fromcare on the part of cloud computing providers--choosing more secure operating systems such as Open BSD and Solaris--and keeping those systems carefully configured.A security-conscious computing services providerwould provision each user withits own processors, caches, and memory at any given momentand would clean house between users,reloading the operating system and zeroing all memory.A serious potential danger will be any laws intended toguarantee the ability of law enforcementto monitor computations that they suspect of supporting criminal activity.Back doors of this sort complicate security arrangementswith two devastating consequences.Complexity is the enemy of security.Once Trojan horses are constructed,one can never be sure by whom they will be used.
Word forms in WordNet are represented in their familiar orthography;word meanings are represented by synonym sets (synsets)- lists of synonymous word forms that are interchangeable in some context.Two kinds of relations are recognized: lexical and semantic.Lexical relations hold between word forms;semantic relations hold between word meanings.To learn more about WordNet, the bookcontaining an updated version of "Five Papers on WordNet"and additional papers by WordNet users .
I've been following the Texai discussion,but I don't see how it overcomes the shortcomings of Cycsuch that it requires a very expensive process ofencoding knowledge explicitly.This may have seemed like a sensible approach in the 1980'swhen we lacked the computing power and training data toimplement statistical approaches.But in hindsight the programming effort was grossly underestimated,and we still don't know.IMHO Cyc failed because it is based on models of artificial languageunrelated to the way children learn natural language.In artificial languages,you have to parse a sentence before you can understand it.In natural language,you have to understand a sentence before you can parse it.
I entirely agree with [that] comment above.The notion of bootstrapping in the Texai English dialog systemis to learn the meanings of the most frequently occurring wordsin the definitions of its yet-to-be-learned vocabulary,and then by reading their definitions,learn the meanings of the remaining wordswith help from a multitude of volunteer mentors.
In particular Matt said:
you have to understand a sentence before you can parse it.An analysis of the word usage frequency in the Texai vocabulary definitionsreveals that knowing perhaps only 10000 frequently occurring wordsshould be enough to understand halfof the whole lexicon of 85000 English words.I acknowledge that there must be a very expensive process ofencoding knowledge explicitly.Like Cycorp's initial approach for DARPA'sRapid Knowledge Formation project,for which I was the first project manager,Texai will use English dialog to rapidly acquire knowledge.I hypothesize that such dialog greatly reduces the expenseof teaching new facts to the system,and also permits a vast multitude of volunteer mentors to divide the effort:many hands make light work.
. far and away the best osx app I have.be sure to enable advanced features,use proxy items, create custom triggers,and read blog posts about things people are doing with it,and watch youtube vids of other customizations...
. The web today does not optimise for human behaviour.When we use it we are usually alone and it is not live.In a Second Life store you can see other people,sit with and talk to them.I envisage we will move a lot of what we are doing on the internet todayinto these more lifelike, 3D spaces.
. a postmortem distributed language-independent debuggerwhose graphical views follow message flowacross process and machine boundaries.An increasing number of developers face the difficult task ofdebugging distributed asynchronous programs.This trend has outpaced the development of adequate debugging tools and currently,the best option for many is an ad hoc patchworkof sequential tools and printf debugging.This paper presents Causeway,a postmortem distributed debugger that demonstrates a novel approachto understanding the behavior of a distributed program.Our message-oriented approach borrows an effective strategy fromsequential debugging:To find the source of unintended side- effects,start with the chain of expressed intentions.We show how Causeway's integrated views- describing both distributed and sequential computation -help users navigate causal pathways as they pursue suspicions.We highlight Causeway's innovative features which include adaptive,customizable event abstraction mechanisms and graphical viewsthat follow message flow across process and machine boundaries.
In this post I will elaborate onwhy some people thinkC-- has more promise than LLVMas a substrate for lazy, functional languages.Let me start by making one thing clear:LLVM does have support for garbage collectors.I am not disputing that.However, as Henderson has shown,so does C and every other language.The question we have to ask is not"Does this environment support garbage collection?"but rather"How efficiently does this environmentsupport garbage collection?".To recap,Henderson's technique involves placingroot pointers(the set of pointers which can befollowed to find all live data)on a shadow stack.Since we manage this stack ourself,it shouldn't be a problem for the GC to walk it.In short, each heap allocation incursan unnecessary stack allocationand heap pointers arenever stored in registers for long.Now what does this mean forlanguages like Haskell?Well, unlike programs written inmore traditional languages,a Haskell application might very welldo between 10 and 20 millionheap allocations per second.Writing Haskell programs is more aboutproducing the correct data streamthan it is about performing the right side-effects. It's common for functions in Haskellto manipulate data without execuingany side-effects. (Think spreadsheets.)This way of computing obviously requiresa very cheap method of allocation.Performing 10 million unnecessarystack allocations per secondwould severely hurt performance,and not having heap pointers in registerscould easily be equally devastating.So what about LLVM?Shouldn't the built-in GC support in LLVMbe more efficient than any cheap hack?Well, it turns out it isn't.The conflict between garbage collectionand optimizations haven't changed,and neither have the solution:disabling or bypassing optimizations.This in turn means unnecessary stack allocationsand sub-optimal use of registers.That LLVM'ers haven't solved the problem ofzero-overhead garbage collectionisn't too surprising. Solving this while staying agnostic of the data modelis an open question in computer science.It is here C-- differs from LLVM. C-- is a research project that aims at solvingdifficult problems such as supporting efficient GCsand cheap concurrency.LLVM, on the other hand, is an engineering project.In conclusion:garbage collection in LLVM incursunacceptable overhead,and while C-- and LLVM do have some overlap,the problems they're trying to solve are quite different.Posted by David Himmelstrup at 11:52 AM
> That LLVM'ers haven't solved the problem ofzero-overhead garbage collection> isn't too surprising .> Solving this while staying agnostic of thedata model> is an open question in computer science.
Well, there is a project at UNSWto translate GHC Core to LLVMRemember: it wasn't clear 10 years agothat LLVM would build up all theinfrastructure C-- wasn't able to. Unfortunately,LLVM has the infrastructure forportable, optimized code,but not the infrastructurefor nice high level language support,that C-- ha(s)d.An interesting projectwould be to target LLVM from C-- ..
C-- is a compiler-target language.The idea is that a compiler for a high-level languagetranslates programs into into C--,leaving the C-- compiler to generate native code.C--'s major goals are these:C-- is not "(write-once, run-anywhere) .It conceals most architecture-specific details,such as the number of registers, but it exposes some.In particular, C-- exposes the word size, byte order,and alignment properties of the target architecture, for two reasons.First, to hide these details would requireintroducing a great deal of complexity, inefficiency, or both-- especially when the front-end compilerneeds to control the representation of its high-level data types.Second, these details are easy to handle in a front-end compiler.Indeed, a compiler may benefit, becauseit can do address arithmetic using integersinstead of symbolic constants such as FloatSize and IntSize.
I do not understand the assertion that LLVM is uncooperative.The direction LLVM takes is driven entirely by contributors.I suggest you embrace thisand implement the necessary GC support in LLVM.The devs would likely be happy to help out with any problems;the team is *very* helpful.Furthermore,that support would open the door to implementingother similar functional languages in LLVM,rather making more isolated code islands.In the long run, LHC will win *big*by having that same code used by others(and tested, and expanded.)There are many things for which it is reasonable to haveNIH (Not Invented Here syndrome).In 2009, a fast code generator is not one of them.
It's unsolved in the academic sense of the word.Solving it requires research and not engineering.If I knew how to solve it, I definitely would add it to LLVM.It's only unsolved in the general case.I doubt, however, that LLVM is interested in my specific data model(which is in a state of flux, even).
what I want to docan't yet be done by any general-purpose compiler.
LLVM is written in C++, but, like C--, it provides first-class support forintermediate representation written as a text file (described here:http://llvm.org/docs/LangRef.html), which allows you to write yourcompiler in the language that makes the most sense for you.In addition to the feature set of C--, LLVM provides several useful piecesof infrastructure: a C/C++/ObjC front-end based on GCC 4, JIT support,aggressive scalar, vector (SIMD), data layout, and interproceduraloptimizations, support for X86/X86-64/PPC32/PPC64/Sparc/IA-64/Alpha andothers, far better codegen than C--, etc. Further, LLVM has a vibrantcommunity, active development, large organizations using and contributingto it (e.g. Apple), and it is an 'industrial strength' tool, so you don'tspend the majority of your time fighting or working around our bugs :).Like C--, LLVM doesn't provide with a runtime (beyond libc :) ), which canbe a good thing or a bad thing depending on your language (forcing you touse a specific runtime is bad IMHO). I would like to see someone developa runtime to support common functional languages out of the box better(which language designers could optionally use), but no-one has done soyet.OTOH, C-- does have some features thatLLVM does not yet have first class support for.LLVM does not currently support for generating efficient codethat detects integer arithmetic overflow, doesn't expose therounding mode of the machine for FP computation, and does not yet supportmultiple return values, for example.While it is missing some minor features, one of the most importantfeatures of LLVM is that it is relatively easy to extend and modify. Forexample, right now LLVM's integer type system consists of signed andunsigned integers of 1/8/16/32 and 64-bits. Soon, signedness will beeliminated (giving us the equivalent of C--'s bits8/bits16/bits32/bits64integer types) and after that, we plan to generalize the integer types toallow any width (e.g. bits11). This is intended to provide better supportfor people using LLVM for hardware synthesis, but is also useful forprecisely constrainted types like those in Ada (i.e. it communicates valueranges to the optimizer better).> I think the three new things I'd like to see out of C-- are (in rough> order of priority):> 1) x86-64 support> 2) the ability to move/copy a stack frame from one stack to another, and> 3) Some form of inline assembler without having to go to C (necessary for> writting threading primitives in C--)LLVM provides #1 and #3 'out of the box'. #2 requires runtimeinteraction, which would be developed as part of the runtime aspect.For me, one disappointment of the LLVM project so far is that we have notbeen very successful engaging the functional language community. We havepeople that use LLVM as "just another C/C++/Objc compiler", we have peoplethat reuse the extant front-ends and optimizer to target their crazy newarchitectures, and we have mostly-imperative language people (e.g. python)using LLVM as an optimizer and code generator. If we had a fewknowledgable people who wanted to see support for functional languagesexcel, I believe LLVM could become the premier host for the functionalcommunity.If you are considering developing aggressive new languages, I stronglyrecommend you check out LLVM. The llvmdev mailing listis a great place to ask questions.
The OCaml Journal has published around 40 articles now. The most popular andthird most popular articles are both about LLVM. So I don't think it iscorrect to say that "functional language people don't like LLVM". Indeed, Ithought I was a kook for trying to write a compiler for a functional languageusing LLVM until I mentioned it to the OCaml community and half a dozenpeople stepped forward with their own alternatives. :-)
Frame-based systems represent domain knowledge. frames are a notion originally introduced by Marvin Minsky (1975)in the seminal paper"A framework for representing knowledge" .. prior to that, domain knowledge was represented byrule-based and logic-based formalisms .Minsky proposed organizing knowledge into chunks called frames.These frames are supposed to capture the essence ofconcepts or stereotypical situations,by clustering all relevant information for these situations together.Important descendants of frame-based representation formalismsare description logicsthat capture the declarative part of frames using a logic-based semantics.Most of these logics are decidable fragments of first order logicand are very closely related to other formalismssuch as modal logics and feature logics.. Minsky's 1975 ideas were evolved into FRL and KRL(Bobrow and Winograd 1977).KRL addressed almost every representational problemdiscussed in the literature.-- a very rich repertoire and almost unlimited flexibility.Features that are common to FRL, KRL, and later frame-based systems(Fikes and Kehler 1985) are:(1) frames are organized in (tangled) hierarchies;(2) frames are composed out of slots (attributes)for which fillers (scalar values, references to other frames or procedures)have to be specified or computed; and(3) properties (fillers, restriction on fillers, etc.)are inherited from superframes to subframes in the hierarchyaccording to some inheritance strategy.
. from math, a monotone function is order-preserving:x less than y impliesf(x) less than f(y),. monotonic logic is a formal logic whose consequence relationis monotonicmeaning that adding a formula to a theorynever produces a reduction of its set of consequences.Intuitively,monotonicity indicates that learning a new piece of knowledgecannot reduce the set of what is known.A monotonic logic cannot handle various reasoning taskssuch as reasoning by default(consequences may be derived only because oflack of evidence of the contrary),abductive reasoning(consequences are only deduced as most likely explanations)and some important approaches to reasoning about knowledge(the ignorance of a consequence must be retractedwhen the consequence becomes known)and similarly belief revision(new knowledge may contradict old beliefs).An example of a default assumption is that the typical bird flies.As a result, if a given animal is known to be a bird, and nothing else is known,it can be assumed to be able to fly.The default assumption must however be retracted if it is later learnedthat the considered animal is a penguin.This example shows that a logic that models default reasoningshould not be monotonic.
frame lang's are found in the context of inheritance networks. these are building relations, eg the assertion prop(x)is represented as a positive link x -> (class for which prop is true)while a complementary assertion can have a negative linknonmonotonic system permits exceptions to inherited propertieseg, neg'links can override pos'links .. the type systems of oopl's are unipolar (positive linking only) monotonicbut frame systems (eg FRL) are unipolar non-monotonic .homogeneous inheritance system (unlike hetero)are one or the other but not both of{ monotonic: all links are strict, thoroughly nonmonotonic: links are defeasible} the concern of this paper isnon-mono homo multiple inheritance systems
. a property of many logic systemsthat states that the hypotheses of any derived factmay be freely extended with additional assumptions.Any true statement in a logic with this propertycontinues to be true, even after adding new axioms.Logics with this property may be called monotonic,to differentiate them from non-monotonic logic.
. typing systems that work similarly to frame'based kb systemsare termed prototype-based languages that use delegation:the language runtime is capable of dispatching the correct methodor finding the right piece of data simply by following a series ofdelegation pointers (from object to its prototype)until a match is found.As such, the child object can continue to be modifiedand amended over time without rearranging the structure of its associated prototypeas in class-based systems.It is also important to note that not only data but also methodscan be added or changed.For this reason, most prototype-based languagesrefer to both data and methods as "slots".Metaobjects are lightweight classes that have but a single instance(the metaobject's referent)A metaobject contains an explicit reference to its referent.An object, working in tandem with a metaobject,is functionally similar to a SELF object that describes its own behavior.
. any entity that manipulates, creates, describes, or implements other objects.The object that the metaobject is about is called the base object.Some information that a metaobject might storeis the base object's type, interface, class, methods,attributes, variables, functions, control structures, etc.A metaobject protocol (MOP)is an interpreter of the semantics of a program that is open and extensible.Therefore, a MOP determines what a program meansand what its behavior is,and it is extensible in that a programmer (or metaprogrammer)can alter program behavior by extending parts of the MOP.The MOP exposes some or all internal structure of the interpreterto the programmer.The MOP may manifest as a set of classes and methodsthat allow a program to inspect the state of the supporting systemand alter its behaviour.MOPs are implemented as object-oriented programswhere all objects are metaobjects.ompiling process, but do not exist when the program is running.One of the best-known runtime MOPs is the one described in the bookThe Art of the Metaobject Protocol (often referred to as AMOP);One example use of a MOP is to alter the implementation of multiple inheritance.A recurring issue is how to resolve conflicting slots and methods of the superclasses.Typically, language designers select one solution,and language users must live with it.A metaobject protocol is one way to implement aspect-oriented programming languages.Many of the early founders of MOPs, including Gregor Kiczaleshave since moved on to be the primary advocates foraspect-oriented programming.http://en.wikipedia.org/wiki/Aspect-oriented_programmingAspects emerged out of object-oriented programming and computational reflection.AOP languages have functionality similar to, but more restricted thanmetaobject protocols.Aspects relate closely to programming concepts likesubjects, mixins, and delegation.Other ways to use aspect-oriented programming paradigms includeComposition Filtersand the hyperslices approach.Since at least the 1970s, developers have been using forms ofinterception and dispatch-patching that are similar tosome of the implementation techniques for AOP,but these never had the semantics thatthe crosscutting specifications were written in one place.Designers have considered alternative ways to achieve separation of code,such as C#'s partial types,but such approaches lack a quantification mechanismthat allows reaching several join points of the codewith one declarative statement.see alt"Subject-Oriented Programming
an object-oriented software paradigmin which the state (fields) and behavior (methods) of objectsare not seen as intrinsic to the objects themselves,but are provided by various subjective perceptions (ÒsubjectsÓ) of the objects.The term and concepts were first published in September 1993in a conference paper[1] which was later recognized as beingone of the three most influential papers to be presented at the conferencebetween 1986 and 1996[2]. As illustrated in that paper,an analogy is made with the contrast between the philosophical views of Plato and Kantwith respect to the characteristics of ÒrealÓ objects,but applied to software ones.For example, while we may all perceive a tree as having ameasurable height, weight, leaf-mass, etc.,from the point-of view of a bird,a tree may also have measures of relative value for food or nesting purposes,or from the point-of-view of a tax-assessor,it may have a certain taxable value in a given year.Neither the bird's nor the tax-assessor's additional state informationneed be seen as intrinsic to the tree,but are added by the perceptions of the bird and tax-assessor,and from Kant's analysis,the same may be true even of characteristics we think of as intrinsic.Like aspect-oriented programming,subject-oriented programming, composition filters, feature oriented programmingand adaptive methodsare considered to be aspect-oriented software development approaches.
Further advances in FOSD arose from recognizing the following facts:Every program has multiple representations(e.g., source, makefiles, documentation, etc.)and adding a feature to a program could elaborate each of its representationsso that all representations are consistent.
The language in which the metaprogram is written is called the metalanguage.The language of the programs that are manipulated is called the object language.The ability of a programming language to be its own metalanguageis called reflection or reflexivity.Having the programming language itself as a first-class data type(as in Lisp, Forth or Rebol) is also very useful.Generic programming invokes a metaprogramming facility within a language,in those languages supporting it.generative programming vs incremental compilation vs modifiable at runtime:. the compiler is a metaprogramming tool;if incremental compilation is available to a programthen metaprogramming can be performed without actually generating source code.In Lisp metaprogramming, the quasiquote operator (typically a comma)introduces code that is evaluated at program definition timerather than at run time.The metaprogramming language is thus identical to the host programming language, and existing Lisp routines can be directly reused for metaprogramming if desired.. in lisp a quote is a hard quote,meaning there is no attention payed to unquote as an escape .. the quasiquote does allow the unquote to work as an escape from quote .
The Accord programming framework supports the development ofautonomic Grid applications .Accord enables runtime composition and autonomic managementof these components using dynamically defined rules.. current (2004) frameworks have interaction patternsthat can't be defined dynamically .. compon'based frameworks don't havethe context-aware self-mgt of individual compon's .. service'based models implicitly assumethat context does not change during app`lifetime .. dynamic context requires autonomic computing,capable of managing themselves using high-level ruleswith minimal human intervention.The Accord programming framework consists of 4 concepts.* an application contextthat defines a common semantic basis for the application.* the definition of autonomic componentsas the building blocks of autonomic applications.* the definition of rules and mechanisms forthe dynamic composition of autonomic components.* an agent infrastructureto support rule enforcement to realize self-managingand dynamic composition behaviors.Accord builds on the AutoMate middleware infrastructurethat provides the essential services required to supportthe development and execution of autonomic applications.( naming service,discovery service,lifecycle management service,and registration service.)
. oop has extremely poor modularity propertieswith respect to class extension and modification.For example, it is easy to override a methodthat should not be overridden,or to reimplement a class in a way thatcauses problems in subclasses.Other large-scale development problems includethe confusion between classes and object types,which limits the construction of abstractions,and the fact that subtype polymorphismis not good enough for expressing container classes .Here are some things that could or shouldbe done to sofware engineering with respect to oop:* Economy of execution.Much can be done to improve the efficiency of method invocationWe also need to design type systems that canstatically check many of the conditions that now requiredynamic subclass checks.* Economy of compilation.the separate compilation of (sub)classes,without resorting to recompilation of superclassesand without relying on "private" information in interfaces.* Economy of small-scale development.improve error detection and the expressiveness of interfaces.* Economy of large-scale development.formulating and enforcing inheritance interfaces:the contract between a class and its subclasses(as opposed to the instantiation interfacewhich is essentially an object type).Parametric polymorphism is beginning to appearand its interactions with object-oriented featuresneed to be better understood.Subtyping and subclassing must be separated.Similarly, classes and interfaces must be separated.* Economy of language features.Prototype-based languages [provide simpler,more composable features with orthogonality] .How can we design powerful engineeringbut also simple and reliable engineering?
