Annotation of loncom/html/adm/help/searchcat.html, revision 1.3
1.1 harris41 1: <html>
2: <head>
3: </head>
4: <body bgcolor='#ffffff'>
5: <a name='helptop' />
6: <img align='right' src='/adm/lonIcons/lonhelplogos.gif' />
7: <h1>Search Catalog</h1>
8: <hr />
9: <form>
10: <input type='button' onClick='self.close()' value='Close this help window' />
11: </form>
12: <ol>
13: <li><a href='#queryconstruct'>Constructing a query</a></li>
14: <li><a href='#scanningstatus'>Understanding the Search Progress screen</a></li>
15: <li><a href='#outputview'>Viewing the Output of Search Results</a>
16: <li><a href='#controlwho'>Controlling who can search through resources</a></li>
17: <li><a href='#engineperformance'>Search engine performance measurements</a>
18: </li>
19: <li><a href='#softwarearchitecture'>Notes on software architecture</a></li>
20: <li><a href='#limitations'>Limitations</a></li>
21: </ol>
22: <a name='queryconstruct' />
23: <a href='#helptop'>
24: <img border='0' align='left' src='/adm/lonIcons/lonhelptop.gif' /></a>
25: <h3>1. Constructing a query</h3>
26: <br clear='all' />
27: <p>
28: Queries are constructed with the three logical operators: AND, OR, and
29: NOT. These logical operators combined with
30: search terms creates a logical expression (Boolean query).
31: Search terms can either be alphanumeric words, or phrases
32: delimited by quotation marks. Logical operations can be
33: grouped together with parentheses.
34: </p>
35: <p>
36: Examples include:
37: </p>
38: <ul>
39: <li><tt>(Harrison and not Albertelli) or (Kortemeyer and "Alexander
40: Sakharuk")</tt></li>
41: <li><tt>not "invariant set" and topology</tt></li>
42: <li><tt>prokaryot or bacteria</tt></li>
43: <li><tt>not einstein and not bohr</tt></li>
44: </ul>
45: <p>
46: The search is case insensitive. (Logical operators are also
47: evaluated in a case insensitive manner, e.g. and=AND.)
48: </p>
49: <br /> <br />
50: <a name='scanningstatus' />
51: <a href='#helptop'>
52: <img border='0' align='left' src='/adm/lonIcons/lonhelptop.gif' /></a>
53: <h3>2. Understanding the Search Progress screen</h3>
54: <br clear='all' />
55: <p>
56: The Search Progress screen provides five pieces of
57: information. This information is dynamically updated
58: every second as the search progresses across the
59: LON-CAPA network.
60: </p>
61: <ol>
62: <li>The number of library servers being scanned.</li>
63: <li>The number of database hits found.</li>
64: <li>The time elapsed (in seconds).</li>
65: <li>A grid showing the response status of every LON-CAPA library server.</li>
66: <li>A window for displaying response details of individual LON-CAPA
67: library servers.</li>
68: </ol>
69: <p>
70: The response status grid consists of the following symbols:
71: </p>
72: <ul>
73: <li><img src='/adm/lonIcons/srvnull.gif' />:
74: unknown; the server has yet to be contacted</li>
75: <li><img src='/adm/lonIcons/srvbad.gif' />:
76: a network connection cannot be established with
77: the server
78: </li>
79: <li><img src='/adm/lonIcons/srvhalf.gif' />:
80: a network connection was established to the
81: database, but search results have yet to be
82: completely transmitted from the database
83: </li>
84: <li><img src='/adm/lonIcons/srvempty.gif' />:
85: a network connection was established and all
86: search results are transmitted; however, there are no
87: matching records for this server for this search
88: </li>
89: <li><img src='/adm/lonIcons/srvgood.gif' />:
90: a network connection was established and all
91: search results are transmitted; there is at least
92: one matching record on this server for this search
93: </li>
94: </ul>
95: <br /> <br />
96: <a name='outputview' />
97: <a href='#helptop'>
98: <img border='0' align='left' src='/adm/lonIcons/lonhelptop.gif' /></a>
99: <h3>3. Viewing the Output of Search Results</h3>
100: <br clear='all' />
101: <p>
102: The interface provides four different ways to format the output
103: of metadata information.
104: <ul>
105: <li><strong>Detailed Citation View</strong></li>
106: <ul>
107: <li><u>Description</u>:
108: Per database record, this view shows the following fields:
109: Owner, Last Revision Date, Title, Author, Subject, Keyword(s), Notes,
110: MIME Type, Language, Copyright/Distribution,
111: Extra custom metadata fields, and Short Abstract.
112: This view is meant to show a nicely formatted, detailed listing
113: of data describing a LON-CAPA resource.
114: </li>
115: <li><u>Example</u>:</li>
116: </ul>
117: <li><strong>Summary View</strong></li>
118: <ul>
119: <li><u>Description</u>:</li>
120: Per database record, this view shows the following fields:
121: Title, Owner, Last Revision Date, Copyright/Distribution, and
122: Extra custom metadata fields.
123: This view is meant to show a nicely formatted, condensed amount
124: of data describing a LON-CAPA resource.
125: <li><u>Example</u>:</li>
126: </ul>
127: <li><strong>Fielded Format</strong></li>
128: <ul>
129: <li><u>Description</u>:</li> This view shows all standard metadata fields
130: (as well as requested custom metadata fields) in the format of
131: <tt><b>field_name</b>: <b>field_value</b></tt>.
132: <li><u>Example</u>:</li>
133: </ul>
134: <li><strong>XML/SGML</strong></li>
135: <ul>
136: <li><u>Description</u>:</li>
137: This view shows all standard metadata fields
138: (as well as requested custom metadata fields) in the format of
139: <tt><b><field_name></b><b>field_value</b><b></field_name></b></tt>.
140: <li><u>Example</u>:</li>
141: </ul>
142: </ul>
143: </p>
144: <br /> <br />
145: <a name='controlwho' />
146: <a href='#helptop'>
147: <img border='0' align='left' src='/adm/lonIcons/lonhelptop.gif' /></a>
148: <h3>4. Controlling who can search through resources</h3>
149: <br clear='all' />
150: <p>
151: Currently, any user can see metadata for any published resource.
152: We are working to change this and are considering two possibilities:
153: </p>
154: <ol>
155: <li>
156: <pre>
157: Browsing and searching should only be
158:
159: * either user specific (georgio can only browse and search
160: /res/DOMAIN/georgio)
1.3 ! albertel 161: * or has advanced status as indicated by $env{'user.adv'}
1.1 harris41 162: </pre>
163: </li>
164: <li>
165: <pre>
166: If user can access resource through current role (student in a
167: class, etc) then it should show up on searching and browsing.
168: Even if resource conditionals prevent actually viewing
169: the specific resource. Advanced users can search and browse
170: "everywhere".
171: </pre>
172: </li>
173: </ol>
174: <br /> <br />
175: <a name='engineperformance' />
176: <a href='#helptop'>
177: <img border='0' align='left' src='/adm/lonIcons/lonhelptop.gif' /></a>
178: <h3>5. Search engine performance measurements</h3>
179: <br clear='all' />
180: <p>
181: </p>
182: <br /> <br />
183: <a name='softwarearchitecture' />
184: <a href='#helptop'>
185: <img border='0' align='left' src='/adm/lonIcons/lonhelptop.gif' /></a>
186: <h3>6. Notes on software architecture</h3>
187: <br clear='all' />
188: <p>
1.2 harris41 189: LON-CAPA is meant to distribute A LOT of educational content
190: to A LOT of people. It is ineffective to directly rely on contents
191: within the ext2 filesystem to be speedily scanned for
192: on-the-fly searches of content descriptions. (Simply put,
193: it takes a cumbersome amount of time to open, read, analyze, and
194: close thousands of files.)
195: </p>
196: <p>
197: The solution is to hash-index various data fields that are
198: descriptive of the educational resources on a LON-CAPA server
199: machine. Descriptive data fields are referred to as
200: "metadata". The question then arises as to how this metadata
201: is handled in terms of the rest of the LON-CAPA network
202: without burdening client and daemon processes. I now
203: answer this question in the format of Problem and Solution
204: below.
205: </p>
206: <p>
207: <pre>
208: PROBLEM SITUATION:
209:
210: If Server A wants data from Server B, Server A uses a lonc process to
211: send a database command to a Server B lond process.
212: lonc= loncapa client process A-lonc= a lonc process on Server A
213: lond= loncapa daemon process
214:
215: database command
216: A-lonc --------TCP/IP----------------> B-lond
217:
218: The problem emerges that A-lonc and B-lond are kept waiting for the
219: MySQL server to "do its stuff", or in other words, perform the conceivably
220: sophisticated, data-intensive, time-sucking database transaction. By tying
221: up a lonc and lond process, this significantly cripples the capabilities
222: of LON-CAPA servers.
223:
224: While commercial databases have a variety of features that ATTEMPT to
225: deal with this, freeware databases are still experimenting and exploring
226: with different schemes with varying degrees of performance stability.
227:
228: THE SOLUTION:
229:
230: A separate daemon process was created that B-lond works with to
231: handle database requests. This daemon process is called "lonsql".
232:
233: So,
234: database command
235: A-lonc ---------TCP/IP-----------------> B-lond =====> B-lonsql
236: <---------------------------------/ |
237: "ok, I'll get back to you..." |
238: |
239: /
240: A-lond <------------------------------- B-lonc <======
241: "Guess what? I have the result!"
242:
243: Of course, depending on success or failure, the messages may vary,
244: but the principle remains the same where a separate pool of children
245: processes (lonsql's) handle the MySQL database manipulations.
246: </pre>
1.1 harris41 247: </p>
248: <br /> <br />
249: <a name='limitations' />
250: <a href='#helptop'>
251: <img border='0' align='left' src='/adm/lonIcons/lonhelptop.gif' /></a>
252: <h3>7. Limitations</h3>
253: <br clear='all' />
254: <p>
255: The metadata search can only consist of spaces and alphanumeric
256: characters. Other characters are illegal and are filtered out
257: when sending the search request to the search engine.
258: </p>
259: <p>
260: LON-CAPA library servers are given 9 seconds to inform
261: another server that they are in the process of generating
262: a reply to a search request. Note that this is DIFFERENT
263: than actually conducting the search. Upon initial communication,
264: the individual library servers just send a response key to
265: indicate the name of the results file that is going to be generated.
266: </p>
267: <p>
268: LON-CAPA library servers will only send up
269: to 100 records in response to a search.
270: </p>
271: <p>
272: The output of matching records is limited
273: to 200 records.
274: </p>
275: <p>
276: The capping of results to values of 100 and 200
277: should eventually be user modifiable. These limitations
278: exist to avoid processing overly expansive search requests.
279: </p>
280: <br /> <br />
281: </body>
282: </html>
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