======= 2.2.2.3.2.3 Distributed Applications =======
[[dido:public:ra:1.2_views:2_tech_views:2-nodenet:3_nodearch:3_xdata| return to Ancillary Data ]]

One of the major extensions to the original Satoshi Nakamoto [1] [27] papers on peer-to-peer electronic cash systems is the use of oracles to access external data and [[dido:public:ra:xapend:xapend.a_glossary:s:smart_contract]] to enforce business rules on ledger transactions. For example, an account holder wants to transfer Bitcoins from one account to another, but there is a “reserve” placed on the account to cover potential debts from option trading. This “reserve” information would not be part of the [[dido:public:ra:xapend:xapend.a_glossary:l:ledger]], but would be ancillary data. The enforcement of the “reserve” is done by a [[dido:public:ra:xapend:xapend.a_glossary:d:dapp|distributed application]] called a smart contract.

  : //A distributed application is software that is executed or runs on multiple computers within a network. These applications interact in order to achieve a specific [[dido:public:ra:xapend:xapend.a_glossary:g:goal|goal]] or task. Traditional applications relied on a single system to run them. Even in the [[dido:public:ra:xapend:xapend.a_glossary:c:client-server|client-server]] model, the application software had to run on either the [[dido:public:ra:xapend:xapend.a_glossary:c:client]], or the [[dido:public:ra:xapend:xapend.a_glossary:s:server|server]] that the client was accessing. However, distributed applications run on both simultaneously.//

  : //With distributed applications, if a [[dido:public:ra:xapend:xapend.a_glossary:n:node|node]] that is running a particular application goes down, another node can resume the task.// ((Techopedia, "Techopedia Definitions," 1 December 2017. [[https://www.techopedia.com/definition/23971/distributed-application]]. ))

A distributed application (DApp) is software that is executed or runs on multiple computers within a network simultaneously. The software is deterministic meaning that given the same inputs, they all produce the same outputs. One of the main benefits of DApps is they are extremely durable and hardened against a single point of failure. Therefore, to be distributed, deterministic and durable, any services that the DApp must interact with must also be distributed, deterministic, and durable. This makes [[dido:public:ra:xapend:xapend.a_glossary:d:dapp]] interaction with traditional client/server cloud services difficult. Naturally, cloud services applications such as [[dido:public:ra:xapend:xapend.a_glossary:s:saas]] and [[dido:public:ra:xapend:xapend.a_glossary:d:daas| Data as a Service (DaaS)]] have some redundancy and reliability built into them; however, they cannot achieve the same level of robustness as a DApp. Therefore, SaaS and DaaS need to expose their functionality using a proxy DApp, which by its nature has latency. This [[dido:public:ra:xapend:xapend.a_glossary:l:latency|latency]] could adversely affect the DApp’s deterministic and durability nature.

Another important aspect of a DApp is that it should be runtime environment agnostic: allowing as many DIDO nodes into the DIDO network as possible. This can be achieved using [[dido:public:ra:xapend:xapend.a_glossary:v:vm]] such as a Java Virtual Machine (JVM) or interpretive engines such as those available with ECMAScript. There are some [[dido:public:ra:xapend:xapend.a_glossary:p:platform|platform]] specific virtual machines available such as the [[dido:public:ra:xapend:xapend.a_glossary:c:clr]] which are not standardized and do not run with the deterministic rigor on non-Windows platforms. Consequently, the list of languages allowable in DApps is limited to those that have a standardized runtime environment (i.e., VM or Engine) that runs on multiple platforms.

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