which is used to share the <i>reverse word index</i> (RWI) to all operators and users of the proxies.
The applied logic of distribution and retrieval of RWI's on the DHT combines all participating proxies to
a <i>Distributed Search Engine</i>.
To point out that this is in contrast to local indexing and searching,
we call it a <i>Global Search Engine</i>.
</p>
<h3>Is there a central server? Does the search engine network need one?</h3>
<p>No. The network architecture does not need a central server, and there is none.
In fact there is a root server which is the 'first' peer, but any other peer has the same rights and tasks to perform.
We still distinguish three different <i>classes</i> of peers:
<ul>
<li><i>junior</i> peers are peers that cannot be reached from the internet because of routing problems or firewall settings;</li>
<li><i>senior</i> peers can be accessed by other peers and</li>
<li><i>principal</i> peers are like senior but can also upload network bootstrap information to ftp/http sites; this is necessary for the network bootstraping.</li>
Junior peers can contribute to the network by submitting index files to senior/principal peers without being asked. (This function is currently very limited)
If your peer is in Senior Mode, it is an access point for index sharing and distribution. It can be contacted for search requests and it collects index files from other peers. If your peer is in Junior Mode, it collects index files from your browsing and distributes them only to other Senior peers, but does not collect index files.
<p>Some p2p-based file sharing software assign non-contributing peers very low priority. We think that that this is not always fair since sometimes the operator does not have the choice of opening the firewall or configuring the router accordingly. Our idea of 'information wares' and their exchange can also be applied to junior peers: they must contribute to the global index by submitting their index <i>actively</i>, while senior peers contribute <i>passively</i>.
But enough senior peers are needed to make this architecture functional. Since any peer contributes almost equally, either actively or passively, you should decide to run in Senior Mode if you can.
We wanted to avoid that you start a search service ony for that very time when you submit a search query. This would give the Search Engine too little online time. So we looked for a cause the you would like to run the Search Engine during all the time that you are online. By giving you the additional value of a caching proxy, the reason was found. The built-in blacklist (url filter, useful i.e. to block ads) for the proxy is another increase in value.
</p>
<h3>Why is this Proxy also a Search Engine?</h3>
<p>YaCy has a built-in <i>caching</i> proxy, which means that YaCy has a lot of indexing information
'for free' without crawling. This may not be a very usual function of a proxy, but a very useful one:
you see a lot of information when you browse the internet and maybe you would like to search exactly
only what you have seen. Beside this interesting feature, you can use YaCy to index an intranet
simply by using the proxy; you don't need to additionally set up another search/indexing process or databases.
YaCy gives you an 'instant' database and an 'instant' search service.</p>
<h3>My YaCy says it runs in 'Junior Mode'. How can I run it in Senior Mode?</h3>
If you want to add your own code, you are welcome; but please contact the author first and discuss your idea to see how it may fit into the overall architecture.
