MKWS Target Selection
=====================


MKWS accesses targets using the Pazpar2 metasearching engine, almost
always fronted by the Service Proxy to manage target selection. This
document assumes the SP is used, and so that a library of targets is
available, maintained using an instance of MKAdmin (often
http://mkc-admin.indexdata.com/console/)


1. Selecting targets within the library
---------------------------------------

MKWS applications can choose what subset of the library's targets to
use, by means of several alternative settings on individual widgets or
in the mkws_config structure:

* targets -- contains a Pazpar2 targets string, typically of the form
  "pz:id=" or "pz:id~" followed by a pipe-separated list of low-level
  target IDs.

  At present, these IDs can take one of two forms, depending on the
  configuration of the Service Proxy being used: they may be based on
  ZURLs, so a typical value would be something like:
	pz:id=josiah.brown.edu:210/innopac|lui.indexdata.com:8080/solr4/select?fq=database:4902
  Or they may be UDBs, so a typical value would be something like:
	pz:id=brown|artstor

* targetfilter -- contains a CQL query which is used to find relevant
  targets from the relvant library. For example,
	udb==Google_Images
  Or
	categories=news

* target -- contains a single UDB, that of the sole target to be
  used. For example
	Google_Images
  This is merely syntactic sugar for "targetfilter" with the query
	udb==NAME


2. Changing the library
-----------------------

Some MKWS applications will be content to use the default library with
its selection of targets. Most, though, will want to define their own
library providing a different range of available targets. An important
case is that of applications that authenticate onto subscription
resources by means of credentials stored in MKAdmin: precautions must
be taken so that such library accounts do not allow unauthorised
access.

Setting up such a library is a two or three-stage process.

Stage A (on MKAdmin)

Create the library:
	- Make a new library on http://mkc-admin.indexdata.com/console/
	- Select relevant targets
	- Add authentication credentials to the targets as necessary
	- Create an end-user account
	- Set its username and password

Stage B (on the application's web-server):

### simple SP URLs

Stage C (optional)

### Fix description

Authentication onto the library can be achieved by a single HTTP GET
to the relevant Service Proxy, passing in the credentials and thereby
initiating an HTTP session. This can most simply be done just by
setting the service_proxy_auth configuration item to a URL such as
	http://mkws.indexdata.com/service-proxy/?command=auth&action=check,login&username=MIKE&password=SWORDFISH
which is usually done with JavaScript like:

	<script type="text/javascript">
	  var mkws_config = { service_proxy_auth:
	  "http://mkws.indexdata.com/service-proxy/?command=auth&action=check,login&username=MIKE&password=SWORDFISH" };
        </script>

However, doing so reveals the the credentials to public view -- to
anyone who does View Source on the MKWS application. This may be
acceptable for some libraries, but is intolerable for those which
provide authenticated access to subscription resources. For such
circumstances, a more elaborate approach is necessary. The idea is to
make a local URL that is used for authentication onto the Service
Proxy, hiding the credentials, and to use local mechanisms to limit
access to that local authentication URL. Here is one way to do it when
Apache2 is the application's web-server, which we will call
example.com:

	- Add a rewriting authentication alias to the configuration:
		RewriteEngine on
		RewriteRule /spauth/ http://mkws.indexdata.com/service-proxy/?command=auth&action=check,login&username=U&password=PW [P]
	- Set thwe MKWS configuration item "service_proxy_auth" to:
		http://example.com/spauth/
	- Protect access to http://example.com/spauth/ (e.g. using a .htaccess file).

Once such a library has been set up, and access to it established,
target selection within the set that it makes available can be done
using the mechanisms above.