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The Signature is a token of identity and identification.

In the world of components and services, signatures denote the characteristic syntax associated with a component or service interface.

Doctrine of Signatures - from Herbal Medicine to Modern Services

Signature as Token of Identity - The Case of Guy Fawkes

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Doctrine of Signatures - from Herbal Medicine to Modern Services

veryard projects > sebpc > signature > doctrine

In the past, many practitioners of herbal medicine believed that visual inspection of a plant could determine its medical properties. For example, the seeds of Skullcap (used as a headache remedy) look like miniature skulls; while the white spotted leaves of Lungwort (a traditional remedy for tuberculosis) look like the lungs of a diseased patient. This belief is known as the Doctrine of Signatures.

As it happens, a surprising number of herbal remedies fit this doctrine. However, this could possibly be explained by the fact that much of the discovery of medicinal plants was carried out by people who believed in the Doctrine of Signatures; and so their researches were not randomly distributed.

Since there are vast numbers of plants, each of which can be prepared in numerous ways; and since there are many diseases that may take different forms in different patients; the Doctrine of Signatures provides a way of reducing the complexity of the discovery process. However, herbalists have accumulated knowledge about these herbs from practical use of these herbs over many centuries, and this means they are no longer dependent on the Doctrine of Signatures alone for knowledge of the proper use of a medicinal plant.

Nowadays, even many practising herbalists regard the Doctrine of Signatures with interested scepticism. Many others may dismiss it as arrant superstition. So what has this got to do with the latest technology such as web services?

As the science fiction writer Arthur C. Clarke once observed, any sufficiently advanced technology is akin to magic, and attitudes towards new technology often border on superstition. In the case of web services, many people adhere to a modern version of the Doctrine of Signatures, by which services can be discovered and understood by looking at their signature.

The signature of a web service is inscribed in WSDL. If we accepted the Doctrine of Signatures, the service lifecycle would simply involve coding the signature of a web service, and publishing it for potential consumers; service consumers would search through these signatures for a suitable "remedy" for their system needs, and use the signature to guide their consumption of the service.

But even in herbal medicine, the Doctrine of Signatures does not tell the whole story about a plant. The ancients identified willow bark as a remedy for rheumatism, by observing the damp environment in which willow trees grow. Willow bark contains what we now know as aspirin, but the Doctrine of Signatures failed to identify the many other potential medical uses of aspirin. Furthermore, the Doctrine of Signatures tells us nothing about the proper preparation and use of a herb, the proper dose, and the possible interactions (synergy or interference) between multiple herbal remedies.

Similarly, a WSDL signature does not provide a full specification of a web service it tells us nothing about its performance, side-effects or possible interactions. Reliance on WSDL limits the potential reuse of a web service. Although it plays a useful role in the deployment of web services, it is not all you need for the management of the service lifecycle.


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Signature as Identity Token - Guy Fawkes

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After his attempt to blow up the Houses of Parliament, Guy Fawkes was taken to the Tower of London and tortured to extract a confession. His signature - an important token of identity - degenerated under torture, and on his confession it is barely legible.

There are serious questions about the validity and authenticity of confessions extracted under torture. The Guy Fawkes example indicates that the identity of the person signing the confession may be brutally transformed by torture, or perhaps even destroyed.  We also know that identity and character may be tranformed by brainwashing - which we may sometimes regard as just another more subtle form of violence.  In other contexts, identity may be altered by advertising or other modes of influence.
 
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This page last updated on November 3rd, 2003
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